Full Code of drone/envsubst for AI

Repository: drone/envsubst
Branch: master
Commit: 179042472c46
Files: 18
Total size: 50.0 KB

Directory structure:
gitextract_1ivk2yvi/

├── .drone.yml
├── .gitignore
├── LICENSE
├── cmd/
│   └── envsubst/
│       └── main.go
├── eval.go
├── eval_test.go
├── funcs.go
├── funcs_test.go
├── go.mod
├── go.sum
├── parse/
│   ├── node.go
│   ├── parse.go
│   ├── parse_test.go
│   ├── scan.go
│   └── scan_test.go
├── path/
│   └── match.go
├── readme.md
└── template.go

================================================
FILE CONTENTS
================================================

================================================
FILE: .drone.yml
================================================
kind: pipeline
name: default

steps:
- name: build
  image: golang:1.11
  commands:
  - go test -v ./...


================================================
FILE: .gitignore
================================================
/envsubst
coverage.out


================================================
FILE: LICENSE
================================================
MIT License

Copyright (c) 2017 drone.io

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.


================================================
FILE: cmd/envsubst/main.go
================================================
package main

import (
	"bufio"
	"fmt"
	"log"
	"os"

	"github.com/drone/envsubst/v2"
)

func main() {
	stdin := bufio.NewScanner(os.Stdin)
	stdout := bufio.NewWriter(os.Stdout)

	for stdin.Scan() {
		line, err := envsubst.EvalEnv(stdin.Text())
		if err != nil {
			log.Fatalf("Error while envsubst: %v", err)
		}
		_, err = fmt.Fprintln(stdout, line)
		if err != nil {
			log.Fatalf("Error while writing to stdout: %v", err)
		}
		stdout.Flush()
	}
}



================================================
FILE: eval.go
================================================
package envsubst

import "os"

// Eval replaces ${var} in the string based on the mapping function.
func Eval(s string, mapping func(string) string) (string, error) {
	t, err := Parse(s)
	if err != nil {
		return s, err
	}
	return t.Execute(mapping)
}

// EvalEnv replaces ${var} in the string according to the values of the
// current environment variables. References to undefined variables are
// replaced by the empty string.
func EvalEnv(s string) (string, error) {
	return Eval(s, os.Getenv)
}


================================================
FILE: eval_test.go
================================================
package envsubst

import "testing"

// test cases sourced from tldp.org
// http://www.tldp.org/LDP/abs/html/parameter-substitution.html

func TestExpand(t *testing.T) {
	var expressions = []struct {
		params map[string]string
		input  string
		output string
	}{
		// text-only
		{
			params: map[string]string{},
			input:  "abcdEFGH28ij",
			output: "abcdEFGH28ij",
		},
		// length
		{
			params: map[string]string{"var01": "abcdEFGH28ij"},
			input:  "${#var01}",
			output: "12",
		},
		// uppercase first
		{
			params: map[string]string{"var01": "abcdEFGH28ij"},
			input:  "${var01^}",
			output: "AbcdEFGH28ij",
		},
		// uppercase
		{
			params: map[string]string{"var01": "abcdEFGH28ij"},
			input:  "${var01^^}",
			output: "ABCDEFGH28IJ",
		},
		// lowercase first
		{
			params: map[string]string{"var01": "ABCDEFGH28IJ"},
			input:  "${var01,}",
			output: "aBCDEFGH28IJ",
		},
		// lowercase
		{
			params: map[string]string{"var01": "ABCDEFGH28IJ"},
			input:  "${var01,,}",
			output: "abcdefgh28ij",
		},
		// substring with position
		{
			params: map[string]string{"path_name": "/home/bozo/ideas/thoughts.for.today"},
			input:  "${path_name:11}",
			output: "ideas/thoughts.for.today",
		},
		// substring with position and length
		{
			params: map[string]string{"path_name": "/home/bozo/ideas/thoughts.for.today"},
			input:  "${path_name:11:5}",
			output: "ideas",
		},
		// default not used
		{
			params: map[string]string{"var": "abc"},
			input:  "${var=xyz}",
			output: "abc",
		},
		// default used
		{
			params: map[string]string{},
			input:  "${var=xyz}",
			output: "xyz",
		},
		{
			params: map[string]string{"default_var": "foo"},
			input:  "something ${var=${default_var}}",
			output: "something foo",
		},
		{
			params: map[string]string{"default_var": "foo1"},
			input:  `foo: ${var=${default_var}-suffix}`,
			output: "foo: foo1-suffix",
		},
		{
			params: map[string]string{"default_var": "foo1"},
			input:  `foo: ${var=prefix${default_var}-suffix}`,
			output: "foo: prefixfoo1-suffix",
		},
		{
			params: map[string]string{},
			input:  "${var:=xyz}",
			output: "xyz",
		},
		// replace suffix
		{
			params: map[string]string{"stringZ": "abcABC123ABCabc"},
			input:  "${stringZ/%abc/XYZ}",
			output: "abcABC123ABCXYZ",
		},
		// replace prefix
		{
			params: map[string]string{"stringZ": "abcABC123ABCabc"},
			input:  "${stringZ/#abc/XYZ}",
			output: "XYZABC123ABCabc",
		},
		// replace all
		{
			params: map[string]string{"stringZ": "abcABC123ABCabc"},
			input:  "${stringZ//abc/xyz}",
			output: "xyzABC123ABCxyz",
		},
		// replace first
		{
			params: map[string]string{"stringZ": "abcABC123ABCabc"},
			input:  "${stringZ/abc/xyz}",
			output: "xyzABC123ABCabc",
		},
		// delete shortest match prefix
		{
			params: map[string]string{"filename": "bash.string.txt"},
			input:  "${filename#*.}",
			output: "string.txt",
		},
		{
			params: map[string]string{"filename": "path/to/file"},
			input:  "${filename#*/}",
			output: "to/file",
		},
		{
			params: map[string]string{"filename": "/path/to/file"},
			input:  "${filename#*/}",
			output: "path/to/file",
		},
		// delete longest match prefix
		{
			params: map[string]string{"filename": "bash.string.txt"},
			input:  "${filename##*.}",
			output: "txt",
		},
		{
			params: map[string]string{"filename": "path/to/file"},
			input:  "${filename##*/}",
			output: "file",
		},
		{
			params: map[string]string{"filename": "/path/to/file"},
			input:  "${filename##*/}",
			output: "file",
		},
		// delete shortest match suffix
		{
			params: map[string]string{"filename": "bash.string.txt"},
			input:  "${filename%.*}",
			output: "bash.string",
		},
		// delete longest match suffix
		{
			params: map[string]string{"filename": "bash.string.txt"},
			input:  "${filename%%.*}",
			output: "bash",
		},

		// nested parameters
		{
			params: map[string]string{"var01": "abcdEFGH28ij"},
			input:  "${var=${var01^^}}",
			output: "ABCDEFGH28IJ",
		},
		// escaped
		{
			params: map[string]string{"var01": "abcdEFGH28ij"},
			input:  "$${var01}",
			output: "${var01}",
		},
		{
			params: map[string]string{"var01": "abcdEFGH28ij"},
			input:  "some text ${var01}$${var$${var01}$var01${var01}",
			output: "some text abcdEFGH28ij${var${var01}$var01abcdEFGH28ij",
		},
		{
			params: map[string]string{"default_var": "foo"},
			input:  "something $${var=${default_var}}",
			output: "something ${var=foo}",
		},
		// some common escaping use cases
		{
			params: map[string]string{"stringZ": "foo/bar"},
			input:  `${stringZ/\//-}`,
			output: "foo-bar",
		},
		{
			params: map[string]string{"stringZ": "foo/bar/baz"},
			input:  `${stringZ//\//-}`,
			output: "foo-bar-baz",
		},
		// escape outside of expansion shouldn't be processed
		{
			params: map[string]string{"default_var": "foo"},
			input:  "\\\\something ${var=${default_var}}",
			output: "\\\\something foo",
		},
		// substitute with a blank string
		{
			params: map[string]string{"stringZ": "foo.bar"},
			input:  `${stringZ/./}`,
			output: "foobar",
		},
	}

	for _, expr := range expressions {
		t.Run(expr.input, func(t *testing.T) {
			t.Logf(expr.input)
			output, err := Eval(expr.input, func(s string) string {
				return expr.params[s]
			})
			if err != nil {
				t.Errorf("Want %q expanded but got error %q", expr.input, err)
			}

			if output != expr.output {
				t.Errorf("Want %q expanded to %q, got %q",
					expr.input,
					expr.output,
					output)
			}
		})
	}
}


================================================
FILE: funcs.go
================================================
package envsubst

import (
	"strconv"
	"strings"
	"unicode"
	"unicode/utf8"

	"github.com/drone/envsubst/v2/path"
)

// defines a parameter substitution function.
type substituteFunc func(string, ...string) string

// toLen returns the length of string s.
func toLen(s string, args ...string) string {
	return strconv.Itoa(len(s))
}

// toLower returns a copy of the string s with all characters
// mapped to their lower case.
func toLower(s string, args ...string) string {
	return strings.ToLower(s)
}

// toUpper returns a copy of the string s with all characters
// mapped to their upper case.
func toUpper(s string, args ...string) string {
	return strings.ToUpper(s)
}

// toLowerFirst returns a copy of the string s with the first
// character mapped to its lower case.
func toLowerFirst(s string, args ...string) string {
	if s == "" {
		return s
	}
	r, n := utf8.DecodeRuneInString(s)
	return string(unicode.ToLower(r)) + s[n:]
}

// toUpperFirst returns a copy of the string s with the first
// character mapped to its upper case.
func toUpperFirst(s string, args ...string) string {
	if s == "" {
		return s
	}
	r, n := utf8.DecodeRuneInString(s)
	return string(unicode.ToUpper(r)) + s[n:]
}

// toDefault returns a copy of the string s if not empty, else
// returns a concatenation of the args without a separator.
func toDefault(s string, args ...string) string {
	if len(s) == 0 && len(args) > 0 {
		// don't use any separator
		s = strings.Join(args, "")
	}
	return s
}

// toSubstr returns a slice of the string s at the specified
// length and position.
func toSubstr(s string, args ...string) string {
	if len(args) == 0 {
		return s // should never happen
	}

	pos, err := strconv.Atoi(args[0])
	if err != nil {
		// bash returns the string if the position
		// cannot be parsed.
		return s
	}

	if pos < 0 {
		// if pos is negative (counts from the end) add it
		// to length to get first character offset
		pos = len(s) + pos

		// if negative offset exceeds the length of the string
		// start from 0
		if pos < 0 {
			pos = 0
		}
	}

	if len(args) == 1 {
		if pos < len(s) {
			return s[pos:]
		}
		// if the position exceeds the length of the
		// string an empty string is returned
		return ""
	}

	length, err := strconv.Atoi(args[1])
	if err != nil {
		// bash returns the string if the length
		// cannot be parsed.
		return s
	}

	if pos+length >= len(s) {
		if pos < len(s) {
			// if the position exceeds the length of the
			// string just return the rest of it like bash
			return s[pos:]
		}
		// if the position exceeds the length of the
		// string an empty string is returned
		return ""
	}

	return s[pos : pos+length]
}

// replaceAll returns a copy of the string s with all instances
// of the substring replaced with the replacement string.
func replaceAll(s string, args ...string) string {
	switch len(args) {
	case 0:
		return s
	case 1:
		return strings.Replace(s, args[0], "", -1)
	default:
		return strings.Replace(s, args[0], args[1], -1)
	}
}

// replaceFirst returns a copy of the string s with the first
// instance of the substring replaced with the replacement string.
func replaceFirst(s string, args ...string) string {
	switch len(args) {
	case 0:
		return s
	case 1:
		return strings.Replace(s, args[0], "", 1)
	default:
		return strings.Replace(s, args[0], args[1], 1)
	}
}

// replacePrefix returns a copy of the string s with the matching
// prefix replaced with the replacement string.
func replacePrefix(s string, args ...string) string {
	if len(args) != 2 {
		return s
	}
	if strings.HasPrefix(s, args[0]) {
		return strings.Replace(s, args[0], args[1], 1)
	}
	return s
}

// replaceSuffix returns a copy of the string s with the matching
// suffix replaced with the replacement string.
func replaceSuffix(s string, args ...string) string {
	if len(args) != 2 {
		return s
	}
	if strings.HasSuffix(s, args[0]) {
		s = strings.TrimSuffix(s, args[0])
		s = s + args[1]
	}
	return s
}

// TODO

func trimShortestPrefix(s string, args ...string) string {
	if len(args) != 0 {
		s = trimShortest(s, args[0])
	}
	return s
}

func trimShortestSuffix(s string, args ...string) string {
	if len(args) != 0 {
		r := reverse(s)
		rarg := reverse(args[0])
		s = reverse(trimShortest(r, rarg))
	}
	return s
}

func trimLongestPrefix(s string, args ...string) string {
	if len(args) != 0 {
		s = trimLongest(s, args[0])
	}
	return s
}

func trimLongestSuffix(s string, args ...string) string {
	if len(args) != 0 {
		r := reverse(s)
		rarg := reverse(args[0])
		s = reverse(trimLongest(r, rarg))
	}
	return s
}

func trimShortest(s, arg string) string {
	var shortestMatch string
	for i := 0; i < len(s); i++ {
		match, err := path.Match(arg, s[0:len(s)-i])

		if err != nil {
			return s
		}

		if match {
			shortestMatch = s[0 : len(s)-i]
		}
	}

	if shortestMatch != "" {
		return strings.TrimPrefix(s, shortestMatch)
	}

	return s
}

func trimLongest(s, arg string) string {
	for i := 0; i < len(s); i++ {
		match, err := path.Match(arg, s[0:len(s)-i])

		if err != nil {
			return s
		}

		if match {
			return strings.TrimPrefix(s, s[0:len(s)-i])
		}
	}

	return s
}

func reverse(s string) string {
	r := []rune(s)
	for i, j := 0, len(r)-1; i < len(r)/2; i, j = i+1, j-1 {
		r[i], r[j] = r[j], r[i]
	}
	return string(r)
}


================================================
FILE: funcs_test.go
================================================
package envsubst

import "testing"

func Test_len(t *testing.T) {
	got, want := toLen("Hello World"), "11"
	if got != want {
		t.Errorf("Expect len function to return %s, got %s", want, got)
	}
}

func Test_lower(t *testing.T) {
	got, want := toLower("Hello World"), "hello world"
	if got != want {
		t.Errorf("Expect lower function to return %s, got %s", want, got)
	}
}

func Test_lowerFirst(t *testing.T) {
	got, want := toLowerFirst("HELLO WORLD"), "hELLO WORLD"
	if got != want {
		t.Errorf("Expect lowerFirst function to return %s, got %s", want, got)
	}
	defer func() {
		if recover() != nil {
			t.Errorf("Expect empty string does not panic lowerFirst")
		}
	}()
	toLowerFirst("")
}

func Test_upper(t *testing.T) {
	got, want := toUpper("Hello World"), "HELLO WORLD"
	if got != want {
		t.Errorf("Expect upper function to return %s, got %s", want, got)
	}
}

func Test_upperFirst(t *testing.T) {
	got, want := toUpperFirst("hello world"), "Hello world"
	if got != want {
		t.Errorf("Expect upperFirst function to return %s, got %s", want, got)
	}
	defer func() {
		if recover() != nil {
			t.Errorf("Expect empty string does not panic upperFirst")
		}
	}()
	toUpperFirst("")
}

func Test_default(t *testing.T) {
	got, want := toDefault("Hello World", "Hola Mundo"), "Hello World"
	if got != want {
		t.Errorf("Expect default function uses variable value")
	}

	got, want = toDefault("", "Hola Mundo"), "Hola Mundo"
	if got != want {
		t.Errorf("Expect default function uses default value, when variable empty. Got %s, Want %s", got, want)
	}

	got, want = toDefault("", "Hola Mundo", "-Bonjour le monde", "-Halló heimur"), "Hola Mundo-Bonjour le monde-Halló heimur"
	if got != want {
		t.Errorf("Expect default function to use concatenated args when variable empty. Got %s, Want %s", got, want)
	}
}

func Test_substr(t *testing.T) {
	got, want := toSubstr("123456789123456789", "0", "8"), "12345678"
	if got != want {
		t.Errorf("Expect substr function to cut from beginning to length")
	}

	got, want = toSubstr("123456789123456789", "1", "8"), "23456789"
	if got != want {
		t.Errorf("Expect substr function to cut from offset to length")
	}

	got, want = toSubstr("123456789123456789", "9"), "123456789"
	if got != want {
		t.Errorf("Expect substr function to cut beginnging with offset")
	}

	got, want = toSubstr("123456789123456789", "9", "50"), "123456789"
	if got != want {
		t.Errorf("Expect substr function to ignore length if out of bound")
	}

	got, want = toSubstr("123456789123456789", "-3", "2"), "78"
	if got != want {
		t.Errorf("Expect substr function to count negative offsets from the end")
	}

	got, want = toSubstr("123456789123456789", "-300", "3"), "123"
	if got != want {
		t.Errorf("Expect substr function to cut from the beginning to length for negative offsets exceeding string length")
	}
	
	got, want = toSubstr("12345678", "9", "1"), ""
	if got != want {
		t.Errorf("Expect substr function to cut entire string if pos is itself out of bound")
	}
}


================================================
FILE: go.mod
================================================
module github.com/drone/envsubst/v2

require github.com/google/go-cmp v0.2.0

go 1.13


================================================
FILE: go.sum
================================================
github.com/google/go-cmp v0.2.0 h1:+dTQ8DZQJz0Mb/HjFlkptS1FeQ4cWSnN941F8aEG4SQ=
github.com/google/go-cmp v0.2.0/go.mod h1:oXzfMopK8JAjlY9xF4vHSVASa0yLyX7SntLO5aqRK0M=


================================================
FILE: parse/node.go
================================================
package parse

// Node is an element in the parse tree.
type Node interface {
	node()
}

// empty string node
var empty = new(TextNode)

// a template is represented by a tree consisting of one
// or more of the following nodes.
type (
	// TextNode represents a string of text.
	TextNode struct {
		Value string
	}

	// FuncNode represents a string function.
	FuncNode struct {
		Param string
		Name  string
		Args  []Node
	}

	// ListNode represents a list of nodes.
	ListNode struct {
		Nodes []Node
	}

	// ParamNode struct{
	// 	Name string
	// }
	//
	// CaseNode struct {
	// 	Name string
	// 	First bool
	// }
	//
	// LowerNode struct {
	// 	Name string
	// 	First bool
	// }
	//
	// SubstrNode struct {
	// 	Name string
	// 	Pos Node
	// 	Len Node
	// }
	//
	// ReplaceNode struct {
	// 	Name string
	// 	Substring Node
	// 	Replacement Node
	// }
	//
	// TrimNode struct{
	//
	// }
	//
	// DefaultNode struct {
	// 	Name string
	// 	Default Node
	// }
)

// newTextNode returns a new TextNode.
func newTextNode(text string) *TextNode {
	return &TextNode{Value: text}
}

// newListNode returns a new ListNode.
func newListNode(nodes ...Node) *ListNode {
	return &ListNode{Nodes: nodes}
}

// newFuncNode returns a new FuncNode.
func newFuncNode(name string) *FuncNode {
	return &FuncNode{Param: name}
}

// node() defines the node in a parse tree

func (*TextNode) node() {}
func (*ListNode) node() {}
func (*FuncNode) node() {}


================================================
FILE: parse/parse.go
================================================
package parse

import (
	"errors"
)

var (
	// ErrBadSubstitution represents a substitution parsing error.
	ErrBadSubstitution = errors.New("bad substitution")

	// ErrMissingClosingBrace represents a missing closing brace "}" error.
	ErrMissingClosingBrace = errors.New("missing closing brace")

	// ErrParseVariableName represents the error when unable to parse a
	// variable name within a substitution.
	ErrParseVariableName = errors.New("unable to parse variable name")

	// ErrParseFuncSubstitution represents the error when unable to parse the
	// substitution within a function parameter.
	ErrParseFuncSubstitution = errors.New("unable to parse substitution within function")

	// ErrParseDefaultFunction represent the error when unable to parse a
	// default function.
	ErrParseDefaultFunction = errors.New("unable to parse default function")
)

// Tree is the representation of a single parsed SQL statement.
type Tree struct {
	Root Node

	// Parsing only; cleared after parse.
	scanner *scanner
}

// Parse parses the string and returns a Tree.
func Parse(buf string) (*Tree, error) {
	t := new(Tree)
	t.scanner = new(scanner)
	return t.Parse(buf)
}

// Parse parses the string buffer to construct an ast
// representation for expansion.
func (t *Tree) Parse(buf string) (tree *Tree, err error) {
	t.scanner.init(buf)
	t.Root, err = t.parseAny()
	return t, err
}

func (t *Tree) parseAny() (Node, error) {
	t.scanner.accept = acceptRune
	t.scanner.mode = scanIdent | scanLbrack | scanEscape
	t.scanner.escapeChars = dollar

	switch t.scanner.scan() {
	case tokenIdent:
		left := newTextNode(
			t.scanner.string(),
		)
		right, err := t.parseAny()
		switch {
		case err != nil:
			return nil, err
		case right == empty:
			return left, nil
		}
		return newListNode(left, right), nil
	case tokenEOF:
		return empty, nil
	case tokenLbrack:
		left, err := t.parseFunc()
		if err != nil {
			return nil, err
		}

		right, err := t.parseAny()
		switch {
		case err != nil:
			return nil, err
		case right == empty:
			return left, nil
		}
		return newListNode(left, right), nil
	}

	return nil, ErrBadSubstitution
}

func (t *Tree) parseFunc() (Node, error) {
	// Turn on all escape characters
	t.scanner.escapeChars = escapeAll
	switch t.scanner.peek() {
	case '#':
		return t.parseLenFunc()
	}

	var name string
	t.scanner.accept = acceptIdent
	t.scanner.mode = scanIdent

	switch t.scanner.scan() {
	case tokenIdent:
		name = t.scanner.string()
	default:
		return nil, ErrParseVariableName
	}

	switch t.scanner.peek() {
	case ':':
		return t.parseDefaultOrSubstr(name)
	case '=':
		return t.parseDefaultFunc(name)
	case ',', '^':
		return t.parseCasingFunc(name)
	case '/':
		return t.parseReplaceFunc(name)
	case '#':
		return t.parseRemoveFunc(name, acceptHashFunc)
	case '%':
		return t.parseRemoveFunc(name, acceptPercentFunc)
	}

	t.scanner.accept = acceptIdent
	t.scanner.mode = scanRbrack
	switch t.scanner.scan() {
	case tokenRbrack:
		return newFuncNode(name), nil
	default:
		return nil, ErrMissingClosingBrace
	}
}

// parse a substitution function parameter.
func (t *Tree) parseParam(accept acceptFunc, mode byte) (Node, error) {
	t.scanner.accept = accept
	t.scanner.mode = mode | scanLbrack
	switch t.scanner.scan() {
	case tokenLbrack:
		return t.parseFunc()
	case tokenIdent:
		return newTextNode(
			t.scanner.string(),
		), nil
	case tokenRbrack:
		return newTextNode(
			t.scanner.string(),
		), nil
	default:
		return nil, ErrParseFuncSubstitution
	}
}

// parse either a default or substring substitution function.
func (t *Tree) parseDefaultOrSubstr(name string) (Node, error) {
	t.scanner.read()
	r := t.scanner.peek()
	t.scanner.unread()
	switch r {
	case '=', '-', '?', '+':
		return t.parseDefaultFunc(name)
	default:
		return t.parseSubstrFunc(name)
	}
}

// parses the ${param:offset} string function
// parses the ${param:offset:length} string function
func (t *Tree) parseSubstrFunc(name string) (Node, error) {
	node := new(FuncNode)
	node.Param = name

	t.scanner.accept = acceptOneColon
	t.scanner.mode = scanIdent
	switch t.scanner.scan() {
	case tokenIdent:
		node.Name = t.scanner.string()
	default:
		return nil, ErrBadSubstitution
	}

	// scan arg[1]
	{
		param, err := t.parseParam(rejectColonClose, scanIdent)
		if err != nil {
			return nil, err
		}

		// param.Value = t.scanner.string()
		node.Args = append(node.Args, param)
	}

	// expect delimiter or close
	t.scanner.accept = acceptColon
	t.scanner.mode = scanIdent | scanRbrack
	switch t.scanner.scan() {
	case tokenRbrack:
		return node, nil
	case tokenIdent:
		// no-op
	default:
		return nil, ErrBadSubstitution
	}

	// scan arg[2]
	{
		param, err := t.parseParam(acceptNotClosing, scanIdent)
		if err != nil {
			return nil, err
		}
		node.Args = append(node.Args, param)
	}

	return node, t.consumeRbrack()
}

// parses the ${param%word} string function
// parses the ${param%%word} string function
// parses the ${param#word} string function
// parses the ${param##word} string function
func (t *Tree) parseRemoveFunc(name string, accept acceptFunc) (Node, error) {
	node := new(FuncNode)
	node.Param = name

	t.scanner.accept = accept
	t.scanner.mode = scanIdent
	switch t.scanner.scan() {
	case tokenIdent:
		node.Name = t.scanner.string()
	default:
		return nil, ErrBadSubstitution
	}

	// scan arg[1]
	{
		param, err := t.parseParam(acceptNotClosing, scanIdent)
		if err != nil {
			return nil, err
		}

		// param.Value = t.scanner.string()
		node.Args = append(node.Args, param)
	}

	return node, t.consumeRbrack()
}

// parses the ${param/pattern/string} string function
// parses the ${param//pattern/string} string function
// parses the ${param/#pattern/string} string function
// parses the ${param/%pattern/string} string function
func (t *Tree) parseReplaceFunc(name string) (Node, error) {
	node := new(FuncNode)
	node.Param = name

	t.scanner.accept = acceptReplaceFunc
	t.scanner.mode = scanIdent
	switch t.scanner.scan() {
	case tokenIdent:
		node.Name = t.scanner.string()
	default:
		return nil, ErrBadSubstitution
	}

	// scan arg[1]
	{
		param, err := t.parseParam(acceptNotSlash, scanIdent|scanEscape)
		if err != nil {
			return nil, err
		}
		node.Args = append(node.Args, param)
	}

	// expect delimiter
	t.scanner.accept = acceptSlash
	t.scanner.mode = scanIdent
	switch t.scanner.scan() {
	case tokenIdent:
		// no-op
	default:
		return nil, ErrBadSubstitution
	}

	// check for blank string
	switch t.scanner.peek() {
	case '}':
		return node, t.consumeRbrack()
	}

	// scan arg[2]
	{
		param, err := t.parseParam(acceptNotClosing, scanIdent|scanEscape)
		if err != nil {
			return nil, err
		}
		node.Args = append(node.Args, param)
	}

	return node, t.consumeRbrack()
}

// parses the ${parameter=word} string function
// parses the ${parameter:=word} string function
// parses the ${parameter:-word} string function
// parses the ${parameter:?word} string function
// parses the ${parameter:+word} string function
func (t *Tree) parseDefaultFunc(name string) (Node, error) {
	node := new(FuncNode)
	node.Param = name

	t.scanner.accept = acceptDefaultFunc
	if t.scanner.peek() == '=' {
		t.scanner.accept = acceptOneEqual
	}
	t.scanner.mode = scanIdent
	switch t.scanner.scan() {
	case tokenIdent:
		node.Name = t.scanner.string()
	default:
		return nil, ErrParseDefaultFunction
	}

	// loop through all possible runes in default param
	for {
		// this acts as the break condition. Peek to see if we reached the end
		switch t.scanner.peek() {
		case '}':
			return node, t.consumeRbrack()
		}
		param, err := t.parseParam(acceptNotClosing, scanIdent)
		if err != nil {
			return nil, err
		}

		node.Args = append(node.Args, param)
	}
}

// parses the ${param,} string function
// parses the ${param,,} string function
// parses the ${param^} string function
// parses the ${param^^} string function
func (t *Tree) parseCasingFunc(name string) (Node, error) {
	node := new(FuncNode)
	node.Param = name

	t.scanner.accept = acceptCasingFunc
	t.scanner.mode = scanIdent
	switch t.scanner.scan() {
	case tokenIdent:
		node.Name = t.scanner.string()
	default:
		return nil, ErrBadSubstitution
	}

	return node, t.consumeRbrack()
}

// parses the ${#param} string function
func (t *Tree) parseLenFunc() (Node, error) {
	node := new(FuncNode)

	t.scanner.accept = acceptOneHash
	t.scanner.mode = scanIdent
	switch t.scanner.scan() {
	case tokenIdent:
		node.Name = t.scanner.string()
	default:
		return nil, ErrBadSubstitution
	}

	t.scanner.accept = acceptIdent
	t.scanner.mode = scanIdent
	switch t.scanner.scan() {
	case tokenIdent:
		node.Param = t.scanner.string()
	default:
		return nil, ErrBadSubstitution
	}

	return node, t.consumeRbrack()
}

// consumeRbrack consumes a right closing bracket. If a closing
// bracket token is not consumed an ErrBadSubstitution is returned.
func (t *Tree) consumeRbrack() error {
	t.scanner.mode = scanRbrack
	if t.scanner.scan() != tokenRbrack {
		return ErrBadSubstitution
	}
	return nil
}

// consumeDelimiter consumes a function argument delimiter. If a
// delimiter is not consumed an ErrBadSubstitution is returned.
// func (t *Tree) consumeDelimiter(accept acceptFunc, mode uint) error {
// 	t.scanner.accept = accept
// 	t.scanner.mode = mode
// 	if t.scanner.scan() != tokenRbrack {
// 		return ErrBadSubstitution
// 	}
// 	return nil
// }


================================================
FILE: parse/parse_test.go
================================================
package parse

import (
	"testing"

	"github.com/google/go-cmp/cmp"
)

var tests = []struct {
	Text string
	Node Node
}{

	//
	// text only
	//
	{
		Text: "text",
		Node: &TextNode{Value: "text"},
	},
	{
		Text: "}text",
		Node: &TextNode{Value: "}text"},
	},
	{
		Text: "http://github.com",
		Node: &TextNode{Value: "http://github.com"}, // should not escape double slash
	},
	{
		Text: "$${string}",
		Node: &TextNode{Value: "${string}"}, // should not escape double dollar
	},
	{
		Text: "$$string",
		Node: &TextNode{Value: "$string"}, // should not escape double dollar
	},
	{
		Text: `\\.\pipe\pipename`,
		Node: &TextNode{Value: `\\.\pipe\pipename`},
	},

	//
	// variable only
	//
	{
		Text: "${string}",
		Node: &FuncNode{Param: "string"},
	},

	//
	// text transform functions
	//
	{
		Text: "${string,}",
		Node: &FuncNode{
			Param: "string",
			Name:  ",",
			Args:  nil,
		},
	},
	{
		Text: "${string,,}",
		Node: &FuncNode{
			Param: "string",
			Name:  ",,",
			Args:  nil,
		},
	},
	{
		Text: "${string^}",
		Node: &FuncNode{
			Param: "string",
			Name:  "^",
			Args:  nil,
		},
	},
	{
		Text: "${string^^}",
		Node: &FuncNode{
			Param: "string",
			Name:  "^^",
			Args:  nil,
		},
	},

	//
	// substring functions
	//
	{
		Text: "${string:position}",
		Node: &FuncNode{
			Param: "string",
			Name:  ":",
			Args: []Node{
				&TextNode{Value: "position"},
			},
		},
	},
	{
		Text: "${string:position:length}",
		Node: &FuncNode{
			Param: "string",
			Name:  ":",
			Args: []Node{
				&TextNode{Value: "position"},
				&TextNode{Value: "length"},
			},
		},
	},

	//
	// string removal functions
	//
	{
		Text: "${string#substring}",
		Node: &FuncNode{
			Param: "string",
			Name:  "#",
			Args: []Node{
				&TextNode{Value: "substring"},
			},
		},
	},
	{
		Text: "${string##substring}",
		Node: &FuncNode{
			Param: "string",
			Name:  "##",
			Args: []Node{
				&TextNode{Value: "substring"},
			},
		},
	},
	{
		Text: "${string%substring}",
		Node: &FuncNode{
			Param: "string",
			Name:  "%",
			Args: []Node{
				&TextNode{Value: "substring"},
			},
		},
	},
	{
		Text: "${string%%substring}",
		Node: &FuncNode{
			Param: "string",
			Name:  "%%",
			Args: []Node{
				&TextNode{Value: "substring"},
			},
		},
	},

	//
	// string replace functions
	//
	{
		Text: "${string/substring/replacement}",
		Node: &FuncNode{
			Param: "string",
			Name:  "/",
			Args: []Node{
				&TextNode{Value: "substring"},
				&TextNode{Value: "replacement"},
			},
		},
	},
	{
		Text: "${string//substring/replacement}",
		Node: &FuncNode{
			Param: "string",
			Name:  "//",
			Args: []Node{
				&TextNode{Value: "substring"},
				&TextNode{Value: "replacement"},
			},
		},
	},
	{
		Text: "${string/#substring/replacement}",
		Node: &FuncNode{
			Param: "string",
			Name:  "/#",
			Args: []Node{
				&TextNode{Value: "substring"},
				&TextNode{Value: "replacement"},
			},
		},
	},
	{
		Text: "${string/%substring/replacement}",
		Node: &FuncNode{
			Param: "string",
			Name:  "/%",
			Args: []Node{
				&TextNode{Value: "substring"},
				&TextNode{Value: "replacement"},
			},
		},
	},

	//
	// default value functions
	//
	{
		Text: "${string=default}",
		Node: &FuncNode{
			Param: "string",
			Name:  "=",
			Args: []Node{
				&TextNode{Value: "default"},
			},
		},
	},
	{
		Text: "${string:=default}",
		Node: &FuncNode{
			Param: "string",
			Name:  ":=",
			Args: []Node{
				&TextNode{Value: "default"},
			},
		},
	},
	{
		Text: "${string:-default}",
		Node: &FuncNode{
			Param: "string",
			Name:  ":-",
			Args: []Node{
				&TextNode{Value: "default"},
			},
		},
	},
	{
		Text: "${string:?default}",
		Node: &FuncNode{
			Param: "string",
			Name:  ":?",
			Args: []Node{
				&TextNode{Value: "default"},
			},
		},
	},
	{
		Text: "${string:+default}",
		Node: &FuncNode{
			Param: "string",
			Name:  ":+",
			Args: []Node{
				&TextNode{Value: "default"},
			},
		},
	},

	//
	// length function
	//
	{
		Text: "${#string}",
		Node: &FuncNode{
			Param: "string",
			Name:  "#",
		},
	},

	//
	// special characters in argument
	//
	{
		Text: "${string#$%:*{}",
		Node: &FuncNode{
			Param: "string",
			Name:  "#",
			Args: []Node{
				&TextNode{Value: "$%:*{"},
			},
		},
	},

	// text before and after function
	{
		Text: "hello ${#string} world",
		Node: &ListNode{
			Nodes: []Node{
				&TextNode{
					Value: "hello ",
				},
				&ListNode{
					Nodes: []Node{
						&FuncNode{
							Param: "string",
							Name:  "#",
						},
						&TextNode{
							Value: " world",
						},
					},
				},
			},
		},
	},
	// text before and after function with \\ outside of function
	{
		Text: `\\ hello ${#string} world \\`,
		Node: &ListNode{
			Nodes: []Node{
				&TextNode{
					Value: `\\ hello `,
				},
				&ListNode{
					Nodes: []Node{
						&FuncNode{
							Param: "string",
							Name:  "#",
						},
						&TextNode{
							Value: ` world \\`,
						},
					},
				},
			},
		},
	},

	// escaped function arguments
	{
		Text: `${string/\/position/length}`,
		Node: &FuncNode{
			Param: "string",
			Name:  "/",
			Args: []Node{
				&TextNode{
					Value: "/position",
				},
				&TextNode{
					Value: "length",
				},
			},
		},
	},
	{
		Text: `${string/\/position\\/length}`,
		Node: &FuncNode{
			Param: "string",
			Name:  "/",
			Args: []Node{
				&TextNode{
					Value: "/position\\",
				},
				&TextNode{
					Value: "length",
				},
			},
		},
	},
	{
		Text: `${string/position/\/length}`,
		Node: &FuncNode{
			Param: "string",
			Name:  "/",
			Args: []Node{
				&TextNode{
					Value: "position",
				},
				&TextNode{
					Value: "/length",
				},
			},
		},
	},
	{
		Text: `${string/position/\/length\\}`,
		Node: &FuncNode{
			Param: "string",
			Name:  "/",
			Args: []Node{
				&TextNode{
					Value: "position",
				},
				&TextNode{
					Value: "/length\\",
				},
			},
		},
	},
	{
		Text: `${string/position/\/leng\\th}`,
		Node: &FuncNode{
			Param: "string",
			Name:  "/",
			Args: []Node{
				&TextNode{
					Value: "position",
				},
				&TextNode{
					Value: "/leng\\th",
				},
			},
		},
	},

	// functions in functions
	{
		Text: "${string:${position}}",
		Node: &FuncNode{
			Param: "string",
			Name:  ":",
			Args: []Node{
				&FuncNode{
					Param: "position",
				},
			},
		},
	},
	{
		Text: "${string:${stringy:position:length}:${stringz,,}}",
		Node: &FuncNode{
			Param: "string",
			Name:  ":",
			Args: []Node{
				&FuncNode{
					Param: "stringy",
					Name:  ":",
					Args: []Node{
						&TextNode{Value: "position"},
						&TextNode{Value: "length"},
					},
				},
				&FuncNode{
					Param: "stringz",
					Name:  ",,",
				},
			},
		},
	},
	{
		Text: "${string#${stringz}}",
		Node: &FuncNode{
			Param: "string",
			Name:  "#",
			Args: []Node{
				&FuncNode{Param: "stringz"},
			},
		},
	},
	{
		Text: "${string=${stringz}}",
		Node: &FuncNode{
			Param: "string",
			Name:  "=",
			Args: []Node{
				&FuncNode{Param: "stringz"},
			},
		},
	},
	{
		Text: "${string=prefix-${var}}",
		Node: &FuncNode{
			Param: "string",
			Name:  "=",
			Args: []Node{
				&TextNode{Value: "prefix-"},
				&FuncNode{Param: "var"},
			},
		},
	},
	{
		Text: "${string=${var}-suffix}",
		Node: &FuncNode{
			Param: "string",
			Name:  "=",
			Args: []Node{
				&FuncNode{Param: "var"},
				&TextNode{Value: "-suffix"},
			},
		},
	},
	{
		Text: "${string=prefix-${var}-suffix}",
		Node: &FuncNode{
			Param: "string",
			Name:  "=",
			Args: []Node{
				&TextNode{Value: "prefix-"},
				&FuncNode{Param: "var"},
				&TextNode{Value: "-suffix"},
			},
		},
	},
	{
		Text: "${string=prefix${var} suffix}",
		Node: &FuncNode{
			Param: "string",
			Name:  "=",
			Args: []Node{
				&TextNode{Value: "prefix"},
				&FuncNode{Param: "var"},
				&TextNode{Value: " suffix"},
			},
		},
	},
	{
		Text: "${string//${stringy}/${stringz}}",
		Node: &FuncNode{
			Param: "string",
			Name:  "//",
			Args: []Node{
				&FuncNode{Param: "stringy"},
				&FuncNode{Param: "stringz"},
			},
		},
	},
}

func TestParse(t *testing.T) {
	for _, test := range tests {
		t.Log(test.Text)
		t.Run(test.Text, func(t *testing.T) {
			got, err := Parse(test.Text)
			if err != nil {
				t.Error(err)
			}

			if diff := cmp.Diff(test.Node, got.Root); diff != "" {
				t.Errorf(diff)
			}
		})
	}
}


================================================
FILE: parse/scan.go
================================================
package parse

import (
	"unicode"
	"unicode/utf8"
)

// eof rune sent when end of file is reached
var eof = rune(0)

// token is a lexical token.
type token uint

// list of lexical tokens.
const (
	// special tokens
	tokenIllegal token = iota
	tokenEOF

	// identifiers and literals
	tokenIdent

	// operators and delimiters
	tokenLbrack
	tokenRbrack
	tokenQuote
)

// predefined mode bits to control recognition of tokens.
const (
	scanIdent byte = 1 << iota
	scanLbrack
	scanRbrack
	scanEscape
)

// predefined mode bits to control escape tokens.
const (
	dollar byte = 1 << iota
	backslash
	escapeAll = dollar | backslash
)

// returns true if rune is accepted.
type acceptFunc func(r rune, i int) bool

// scanner implements a lexical scanner that reads unicode
// characters and tokens from a string buffer.
type scanner struct {
	buf         string
	pos         int
	start       int
	width       int
	mode        byte
	escapeChars byte

	accept acceptFunc
}

// init initializes a scanner with a new buffer.
func (s *scanner) init(buf string) {
	s.buf = buf
	s.pos = 0
	s.start = 0
	s.width = 0
	s.accept = nil
}

// read returns the next unicode character. It returns eof at
// the end of the string buffer.
func (s *scanner) read() rune {
	if s.pos >= len(s.buf) {
		s.width = 0
		return eof
	}
	r, w := utf8.DecodeRuneInString(s.buf[s.pos:])
	s.width = w
	s.pos += s.width
	return r
}

func (s *scanner) unread() {
	s.pos -= s.width
}

// skip skips over the curring unicode character in the buffer
// by slicing and removing from the buffer.
func (s *scanner) skip() {
	l := s.buf[:s.pos-1]
	r := s.buf[s.pos:]
	s.buf = l + r
}

// peek returns the next unicode character in the buffer without
// advancing the scanner. It returns eof if the scanner's position
// is at the last character of the source.
func (s *scanner) peek() rune {
	r := s.read()
	s.unread()
	return r
}

// string returns the string corresponding to the most recently
// scanned token. Valid after calling scan().
func (s *scanner) string() string {
	return s.buf[s.start:s.pos]
}

// tests if the bit exists for a given character bit
func (s *scanner) shouldEscape(character byte) bool {
	return s.escapeChars&character != 0
}

// scan reads the next token or Unicode character from source and
// returns it. It returns EOF at the end of the source.
func (s *scanner) scan() token {
	s.start = s.pos
	r := s.read()
	switch {
	case r == eof:
		return tokenEOF
	case s.scanLbrack(r):
		return tokenLbrack
	case s.scanRbrack(r):
		return tokenRbrack
	case s.scanIdent(r):
		return tokenIdent
	}
	return tokenIllegal
}

// scanIdent reads the next token or Unicode character from source
// and returns true if the Ident character is accepted.
func (s *scanner) scanIdent(r rune) bool {
	if s.mode&scanIdent == 0 {
		return false
	}
	if s.scanEscaped(r) {
		s.skip()
	} else if !s.accept(r, s.pos-s.start) {
		return false
	}
loop:
	for {
		r := s.read()
		switch {
		case r == eof:
			s.unread()
			break loop
		case s.scanLbrack(r):
			s.unread()
			s.unread()
			break loop
		}
		if s.scanEscaped(r) {
			s.skip()
			continue
		}
		if !s.accept(r, s.pos-s.start) {
			s.unread()
			break loop
		}
	}
	return true
}

// scanLbrack reads the next token or Unicode character from source
// and returns true if the open bracket is encountered.
func (s *scanner) scanLbrack(r rune) bool {
	if s.mode&scanLbrack == 0 {
		return false
	}
	if r == '$' {
		if s.read() == '{' {
			return true
		}
		s.unread()
	}
	return false
}

// scanRbrack reads the next token or Unicode character from source
// and returns true if the closing bracket is encountered.
func (s *scanner) scanRbrack(r rune) bool {
	if s.mode&scanRbrack == 0 {
		return false
	}
	return r == '}'
}

// scanEscaped reads the next token or Unicode character from source
// and returns true if it being escaped and should be skipped.
func (s *scanner) scanEscaped(r rune) bool {
	if s.mode&scanEscape == 0 {
		return false
	}
	if r == '$' && s.shouldEscape(dollar) {
		if s.peek() == '$' {
			return true
		}
	}
	if r == '\\' && s.shouldEscape(backslash) {
		switch s.peek() {
		case '/', '\\':
			return true
		default:
			return false
		}
	}

	return false
}

//
// scanner functions accept or reject runes.
//

func acceptRune(r rune, i int) bool {
	return true
}

func acceptIdent(r rune, i int) bool {
	return unicode.IsLetter(r) || unicode.IsDigit(r) || r == '_'
}

func acceptColon(r rune, i int) bool {
	return r == ':'
}

func acceptOneHash(r rune, i int) bool {
	return r == '#' && i == 1
}

func acceptNone(r rune, i int) bool {
	return false
}

func acceptNotClosing(r rune, i int) bool {
	return r != '}'
}

func acceptHashFunc(r rune, i int) bool {
	return r == '#' && i < 3
}

func acceptPercentFunc(r rune, i int) bool {
	return r == '%' && i < 3
}

func acceptDefaultFunc(r rune, i int) bool {
	switch {
	case i == 1 && r == ':':
		return true
	case i == 2 && (r == '=' || r == '-' || r == '?' || r == '+'):
		return true
	default:
		return false
	}
}

func acceptReplaceFunc(r rune, i int) bool {
	switch {
	case i == 1 && r == '/':
		return true
	case i == 2 && (r == '/' || r == '#' || r == '%'):
		return true
	default:
		return false
	}
}

func acceptOneEqual(r rune, i int) bool {
	return i == 1 && r == '='
}

func acceptOneColon(r rune, i int) bool {
	return i == 1 && r == ':'
}

func rejectColonClose(r rune, i int) bool {
	return r != ':' && r != '}'
}

func acceptSlash(r rune, i int) bool {
	return r == '/'
}

func acceptNotSlash(r rune, i int) bool {
	return r != '/'
}

func acceptCasingFunc(r rune, i int) bool {
	return (r == ',' || r == '^') && i < 3
}


================================================
FILE: parse/scan_test.go
================================================
package parse


================================================
FILE: path/match.go
================================================
// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package path

import (
	"errors"
	"unicode/utf8"
)

// ErrBadPattern indicates a globbing pattern was malformed.
var ErrBadPattern = errors.New("syntax error in pattern")

// Match reports whether name matches the shell file name pattern.
// The pattern syntax is:
//
//	pattern:
//		{ term }
//	term:
//		'*'         matches any sequence of non-/ characters
//		'?'         matches any single non-/ character
//		'[' [ '^' ] { character-range } ']'
//		            character class (must be non-empty)
//		c           matches character c (c != '*', '?', '\\', '[')
//		'\\' c      matches character c
//
//	character-range:
//		c           matches character c (c != '\\', '-', ']')
//		'\\' c      matches character c
//		lo '-' hi   matches character c for lo <= c <= hi
//
// Match requires pattern to match all of name, not just a substring.
// The only possible returned error is ErrBadPattern, when pattern
// is malformed.
//
func Match(pattern, name string) (matched bool, err error) {
Pattern:
	for len(pattern) > 0 {
		var star bool
		var chunk string
		star, chunk, pattern = scanChunk(pattern)
		if star && chunk == "" {
			// Trailing * matches rest of string unless it has a /.
			// return !strings.Contains(name, "/"), nil

			// Return rest of string
			return true, nil
		}
		// Look for match at current position.
		t, ok, err := matchChunk(chunk, name)
		// if we're the last chunk, make sure we've exhausted the name
		// otherwise we'll give a false result even if we could still match
		// using the star
		if ok && (len(t) == 0 || len(pattern) > 0) {
			name = t
			continue
		}
		if err != nil {
			return false, err
		}
		if star {
			// Look for match skipping i+1 bytes.
			for i := 0; i < len(name); i++ {
				t, ok, err := matchChunk(chunk, name[i+1:])
				if ok {
					// if we're the last chunk, make sure we exhausted the name
					if len(pattern) == 0 && len(t) > 0 {
						continue
					}
					name = t
					continue Pattern
				}
				if err != nil {
					return false, err
				}
			}
		}
		return false, nil
	}
	return len(name) == 0, nil
}

// scanChunk gets the next segment of pattern, which is a non-star string
// possibly preceded by a star.
func scanChunk(pattern string) (star bool, chunk, rest string) {
	for len(pattern) > 0 && pattern[0] == '*' {
		pattern = pattern[1:]
		star = true
	}
	inrange := false
	var i int
Scan:
	for i = 0; i < len(pattern); i++ {
		switch pattern[i] {
		case '\\':
			// error check handled in matchChunk: bad pattern.
			if i+1 < len(pattern) {
				i++
			}
		case '[':
			inrange = true
		case ']':
			inrange = false
		case '*':
			if !inrange {
				break Scan
			}
		}
	}
	return star, pattern[0:i], pattern[i:]
}

// matchChunk checks whether chunk matches the beginning of s.
// If so, it returns the remainder of s (after the match).
// Chunk is all single-character operators: literals, char classes, and ?.
func matchChunk(chunk, s string) (rest string, ok bool, err error) {
	for len(chunk) > 0 {
		if len(s) == 0 {
			return
		}
		switch chunk[0] {
		case '[':
			// character class
			r, n := utf8.DecodeRuneInString(s)
			s = s[n:]
			chunk = chunk[1:]
			// possibly negated
			notNegated := true
			if len(chunk) > 0 && chunk[0] == '^' {
				notNegated = false
				chunk = chunk[1:]
			}
			// parse all ranges
			match := false
			nrange := 0
			for {
				if len(chunk) > 0 && chunk[0] == ']' && nrange > 0 {
					chunk = chunk[1:]
					break
				}
				var lo, hi rune
				if lo, chunk, err = getEsc(chunk); err != nil {
					return
				}
				hi = lo
				if chunk[0] == '-' {
					if hi, chunk, err = getEsc(chunk[1:]); err != nil {
						return
					}
				}
				if lo <= r && r <= hi {
					match = true
				}
				nrange++
			}
			if match != notNegated {
				return
			}

		case '?':
			_, n := utf8.DecodeRuneInString(s)
			s = s[n:]
			chunk = chunk[1:]

		case '\\':
			chunk = chunk[1:]
			if len(chunk) == 0 {
				err = ErrBadPattern
				return
			}
			fallthrough

		default:
			if chunk[0] != s[0] {
				return
			}
			s = s[1:]
			chunk = chunk[1:]
		}
	}
	return s, true, nil
}

// getEsc gets a possibly-escaped character from chunk, for a character class.
func getEsc(chunk string) (r rune, nchunk string, err error) {
	if len(chunk) == 0 || chunk[0] == '-' || chunk[0] == ']' {
		err = ErrBadPattern
		return
	}
	if chunk[0] == '\\' {
		chunk = chunk[1:]
		if len(chunk) == 0 {
			err = ErrBadPattern
			return
		}
	}
	r, n := utf8.DecodeRuneInString(chunk)
	if r == utf8.RuneError && n == 1 {
		err = ErrBadPattern
	}
	nchunk = chunk[n:]
	if len(nchunk) == 0 {
		err = ErrBadPattern
	}
	return
}


================================================
FILE: readme.md
================================================
# envsubst

`envsubst` is a Go package for expanding variables in a string using `${var}` syntax.
Includes support for bash string replacement functions.

## Documentation

[Documentation can be found on GoDoc][doc].

## Supported Functions

| __Expression__                | __Meaning__                                                     |
| -----------------             | --------------                                                  |
| `${var}`                      | Value of `$var`
| `${#var}`                     | String length of `$var`
| `${var^}`                     | Uppercase first character of `$var`
| `${var^^}`                    | Uppercase all characters in `$var`
| `${var,}`                     | Lowercase first character of `$var`
| `${var,,}`                    | Lowercase all characters in `$var`
| `${var:n}`                    | Offset `$var` `n` characters from start
| `${var:n:len}`                | Offset `$var` `n` characters with max length of `len`
| `${var#pattern}`              | Strip shortest `pattern` match from start
| `${var##pattern}`             | Strip longest `pattern` match from start
| `${var%pattern}`              | Strip shortest `pattern` match from end
| `${var%%pattern}`             | Strip longest `pattern` match from end
| `${var-default`               | If `$var` is not set, evaluate expression as `$default`
| `${var:-default`              | If `$var` is not set or is empty, evaluate expression as `$default`
| `${var=default`               | If `$var` is not set, evaluate expression as `$default`
| `${var:=default`              | If `$var` is not set or is empty, evaluate expression as `$default`
| `${var/pattern/replacement}`  | Replace as few `pattern` matches as possible with `replacement`
| `${var//pattern/replacement}` | Replace as many `pattern` matches as possible with `replacement`
| `${var/#pattern/replacement}` | Replace `pattern` match with `replacement` from `$var` start
| `${var/%pattern/replacement}` | Replace `pattern` match with `replacement` from `$var` end

For a deeper reference, see [bash-hackers](https://wiki.bash-hackers.org/syntax/pe#case_modification) or [gnu pattern matching](https://www.gnu.org/software/bash/manual/html_node/Pattern-Matching.html).

## Unsupported Functions

* `${var-default}`
* `${var+default}`
* `${var:?default}`
* `${var:+default}`

[doc]: http://godoc.org/github.com/drone/envsubst


================================================
FILE: template.go
================================================
package envsubst

import (
	"bytes"
	"io"
	"io/ioutil"

	"github.com/drone/envsubst/v2/parse"
)

// state represents the state of template execution. It is not part of the
// template so that multiple executions can run in parallel.
type state struct {
	template *Template
	writer   io.Writer
	node     parse.Node // current node

	// maps variable names to values
	mapper func(string) string
}

// Template is the representation of a parsed shell format string.
type Template struct {
	tree *parse.Tree
}

// Parse creates a new shell format template and parses the template
// definition from string s.
func Parse(s string) (t *Template, err error) {
	t = new(Template)
	t.tree, err = parse.Parse(s)
	if err != nil {
		return nil, err
	}
	return t, nil
}

// ParseFile creates a new shell format template and parses the template
// definition from the named file.
func ParseFile(path string) (*Template, error) {
	b, err := ioutil.ReadFile(path)
	if err != nil {
		return nil, err
	}
	return Parse(string(b))
}

// Execute applies a parsed template to the specified data mapping.
func (t *Template) Execute(mapping func(string) string) (str string, err error) {
	b := new(bytes.Buffer)
	s := new(state)
	s.node = t.tree.Root
	s.mapper = mapping
	s.writer = b
	err = t.eval(s)
	if err != nil {
		return
	}
	return b.String(), nil
}

func (t *Template) eval(s *state) (err error) {
	switch node := s.node.(type) {
	case *parse.TextNode:
		err = t.evalText(s, node)
	case *parse.FuncNode:
		err = t.evalFunc(s, node)
	case *parse.ListNode:
		err = t.evalList(s, node)
	}
	return err
}

func (t *Template) evalText(s *state, node *parse.TextNode) error {
	_, err := io.WriteString(s.writer, node.Value)
	return err
}

func (t *Template) evalList(s *state, node *parse.ListNode) (err error) {
	for _, n := range node.Nodes {
		s.node = n
		err = t.eval(s)
		if err != nil {
			return err
		}
	}
	return nil
}

func (t *Template) evalFunc(s *state, node *parse.FuncNode) error {
	var w = s.writer
	var buf bytes.Buffer
	var args []string
	for _, n := range node.Args {
		buf.Reset()
		s.writer = &buf
		s.node = n
		err := t.eval(s)
		if err != nil {
			return err
		}
		args = append(args, buf.String())
	}

	// restore the origin writer
	s.writer = w
	s.node = node

	v := s.mapper(node.Param)

	fn := lookupFunc(node.Name, len(args))

	_, err := io.WriteString(s.writer, fn(v, args...))
	return err
}

// lookupFunc returns the parameters substitution function by name. If the
// named function does not exists, a default function is returned.
func lookupFunc(name string, args int) substituteFunc {
	switch name {
	case ",":
		return toLowerFirst
	case ",,":
		return toLower
	case "^":
		return toUpperFirst
	case "^^":
		return toUpper
	case "#":
		if args == 0 {
			return toLen
		}
		return trimShortestPrefix
	case "##":
		return trimLongestPrefix
	case "%":
		return trimShortestSuffix
	case "%%":
		return trimLongestSuffix
	case ":":
		return toSubstr
	case "/#":
		return replacePrefix
	case "/%":
		return replaceSuffix
	case "/":
		return replaceFirst
	case "//":
		return replaceAll
	case "=", ":=", ":-":
		return toDefault
	case ":?", ":+", "-", "+":
		return toDefault
	default:
		return toDefault
	}
}