// Copyright 2011 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 template

import (
	
	
	
	
	
	
)

// nextJSCtx returns the context that determines whether a slash after the
// given run of tokens starts a regular expression instead of a division
// operator: / or /=.
//
// This assumes that the token run does not include any string tokens, comment
// tokens, regular expression literal tokens, or division operators.
//
// This fails on some valid but nonsensical JavaScript programs like
// "x = ++/foo/i" which is quite different than "x++/foo/i", but is not known to
// fail on any known useful programs. It is based on the draft
// JavaScript 2.0 lexical grammar and requires one token of lookbehind:
// https://www.mozilla.org/js/language/js20-2000-07/rationale/syntax.html
func nextJSCtx( []byte,  jsCtx) jsCtx {
	 = bytes.TrimRight(, "\t\n\f\r \u2028\u2029")
	if len() == 0 {
		return 
	}

	// All cases below are in the single-byte UTF-8 group.
	switch ,  := [len()-1], len();  {
	case '+', '-':
		// ++ and -- are not regexp preceders, but + and - are whether
		// they are used as infix or prefix operators.
		 :=  - 1
		// Count the number of adjacent dashes or pluses.
		for  > 0 && [-1] ==  {
			--
		}
		if (-)&1 == 1 {
			// Reached for trailing minus signs since "---" is the
			// same as "-- -".
			return jsCtxRegexp
		}
		return jsCtxDivOp
	case '.':
		// Handle "42."
		if  != 1 && '0' <= [-2] && [-2] <= '9' {
			return jsCtxDivOp
		}
		return jsCtxRegexp
	// Suffixes for all punctuators from section 7.7 of the language spec
	// that only end binary operators not handled above.
	case ',', '<', '>', '=', '*', '%', '&', '|', '^', '?':
		return jsCtxRegexp
	// Suffixes for all punctuators from section 7.7 of the language spec
	// that are prefix operators not handled above.
	case '!', '~':
		return jsCtxRegexp
	// Matches all the punctuators from section 7.7 of the language spec
	// that are open brackets not handled above.
	case '(', '[':
		return jsCtxRegexp
	// Matches all the punctuators from section 7.7 of the language spec
	// that precede expression starts.
	case ':', ';', '{':
		return jsCtxRegexp
	// CAVEAT: the close punctuators ('}', ']', ')') precede div ops and
	// are handled in the default except for '}' which can precede a
	// division op as in
	//    ({ valueOf: function () { return 42 } } / 2
	// which is valid, but, in practice, developers don't divide object
	// literals, so our heuristic works well for code like
	//    function () { ... }  /foo/.test(x) && sideEffect();
	// The ')' punctuator can precede a regular expression as in
	//     if (b) /foo/.test(x) && ...
	// but this is much less likely than
	//     (a + b) / c
	case '}':
		return jsCtxRegexp
	default:
		// Look for an IdentifierName and see if it is a keyword that
		// can precede a regular expression.
		 := 
		for  > 0 && isJSIdentPart(rune([-1])) {
			--
		}
		if regexpPrecederKeywords[string([:])] {
			return jsCtxRegexp
		}
	}
	// Otherwise is a punctuator not listed above, or
	// a string which precedes a div op, or an identifier
	// which precedes a div op.
	return jsCtxDivOp
}

// regexpPrecederKeywords is a set of reserved JS keywords that can precede a
// regular expression in JS source.
var regexpPrecederKeywords = map[string]bool{
	"break":      true,
	"case":       true,
	"continue":   true,
	"delete":     true,
	"do":         true,
	"else":       true,
	"finally":    true,
	"in":         true,
	"instanceof": true,
	"return":     true,
	"throw":      true,
	"try":        true,
	"typeof":     true,
	"void":       true,
}

var jsonMarshalType = reflect.TypeOf((*json.Marshaler)(nil)).Elem()

// indirectToJSONMarshaler returns the value, after dereferencing as many times
// as necessary to reach the base type (or nil) or an implementation of json.Marshal.
func indirectToJSONMarshaler( interface{}) interface{} {
	// text/template now supports passing untyped nil as a func call
	// argument, so we must support it. Otherwise we'd panic below, as one
	// cannot call the Type or Interface methods on an invalid
	// reflect.Value. See golang.org/issue/18716.
	if  == nil {
		return nil
	}

	 := reflect.ValueOf()
	for !.Type().Implements(jsonMarshalType) && .Kind() == reflect.Ptr && !.IsNil() {
		 = .Elem()
	}
	return .Interface()
}

// jsValEscaper escapes its inputs to a JS Expression (section 11.14) that has
// neither side-effects nor free variables outside (NaN, Infinity).
func jsValEscaper( ...interface{}) string {
	var  interface{}
	if len() == 1 {
		 = indirectToJSONMarshaler([0])
		switch t := .(type) {
		case JS:
			return string()
		case JSStr:
			// TODO: normalize quotes.
			return `"` + string() + `"`
		case json.Marshaler:
			// Do not treat as a Stringer.
		case fmt.Stringer:
			 = .String()
		}
	} else {
		for ,  := range  {
			[] = indirectToJSONMarshaler()
		}
		 = fmt.Sprint(...)
	}
	// TODO: detect cycles before calling Marshal which loops infinitely on
	// cyclic data. This may be an unacceptable DoS risk.
	,  := json.Marshal()
	if  != nil {
		// Put a space before comment so that if it is flush against
		// a division operator it is not turned into a line comment:
		//     x/{{y}}
		// turning into
		//     x//* error marshaling y:
		//          second line of error message */null
		return fmt.Sprintf(" /* %s */null ", strings.ReplaceAll(.Error(), "*/", "* /"))
	}

	// TODO: maybe post-process output to prevent it from containing
	// "<!--", "-->", "<![CDATA[", "]]>", or "</script"
	// in case custom marshalers produce output containing those.
	// Note: Do not use \x escaping to save bytes because it is not JSON compatible and this escaper
	// supports ld+json content-type.
	if len() == 0 {
		// In, `x=y/{{.}}*z` a json.Marshaler that produces "" should
		// not cause the output `x=y/*z`.
		return " null "
	}
	,  := utf8.DecodeRune()
	,  := utf8.DecodeLastRune()
	var  strings.Builder
	// Prevent IdentifierNames and NumericLiterals from running into
	// keywords: in, instanceof, typeof, void
	 := isJSIdentPart() || isJSIdentPart()
	if  {
		.WriteByte(' ')
	}
	 := 0
	// Make sure that json.Marshal escapes codepoints U+2028 & U+2029
	// so it falls within the subset of JSON which is valid JS.
	for  := 0;  < len(); {
		,  := utf8.DecodeRune([:])
		 := ""
		if  == 0x2028 {
			 = `\u2028`
		} else if  == 0x2029 {
			 = `\u2029`
		}
		if  != "" {
			.Write([:])
			.WriteString()
			 =  + 
		}
		 += 
	}
	if .Len() != 0 {
		.Write([:])
		if  {
			.WriteByte(' ')
		}
		return .String()
	}
	return string()
}

// jsStrEscaper produces a string that can be included between quotes in
// JavaScript source, in JavaScript embedded in an HTML5 <script> element,
// or in an HTML5 event handler attribute such as onclick.
func jsStrEscaper( ...interface{}) string {
	,  := stringify(...)
	if  == contentTypeJSStr {
		return replace(, jsStrNormReplacementTable)
	}
	return replace(, jsStrReplacementTable)
}

// jsRegexpEscaper behaves like jsStrEscaper but escapes regular expression
// specials so the result is treated literally when included in a regular
// expression literal. /foo{{.X}}bar/ matches the string "foo" followed by
// the literal text of {{.X}} followed by the string "bar".
func jsRegexpEscaper( ...interface{}) string {
	,  := stringify(...)
	 = replace(, jsRegexpReplacementTable)
	if  == "" {
		// /{{.X}}/ should not produce a line comment when .X == "".
		return "(?:)"
	}
	return 
}

// replace replaces each rune r of s with replacementTable[r], provided that
// r < len(replacementTable). If replacementTable[r] is the empty string then
// no replacement is made.
// It also replaces runes U+2028 and U+2029 with the raw strings `\u2028` and
// `\u2029`.
func replace( string,  []string) string {
	var  strings.Builder
	, ,  := rune(0), 0, 0
	for  := 0;  < len();  +=  {
		// See comment in htmlEscaper.
		,  = utf8.DecodeRuneInString([:])
		var  string
		switch {
		case int() < len(lowUnicodeReplacementTable):
			 = lowUnicodeReplacementTable[]
		case int() < len() && [] != "":
			 = []
		case  == '\u2028':
			 = `\u2028`
		case  == '\u2029':
			 = `\u2029`
		default:
			continue
		}
		if  == 0 {
			.Grow(len())
		}
		.WriteString([:])
		.WriteString()
		 =  + 
	}
	if  == 0 {
		return 
	}
	.WriteString([:])
	return .String()
}

var lowUnicodeReplacementTable = []string{
	0: `\u0000`, 1: `\u0001`, 2: `\u0002`, 3: `\u0003`, 4: `\u0004`, 5: `\u0005`, 6: `\u0006`,
	'\a': `\u0007`,
	'\b': `\u0008`,
	'\t': `\t`,
	'\n': `\n`,
	'\v': `\u000b`, // "\v" == "v" on IE 6.
	'\f': `\f`,
	'\r': `\r`,
	0xe:  `\u000e`, 0xf: `\u000f`, 0x10: `\u0010`, 0x11: `\u0011`, 0x12: `\u0012`, 0x13: `\u0013`,
	0x14: `\u0014`, 0x15: `\u0015`, 0x16: `\u0016`, 0x17: `\u0017`, 0x18: `\u0018`, 0x19: `\u0019`,
	0x1a: `\u001a`, 0x1b: `\u001b`, 0x1c: `\u001c`, 0x1d: `\u001d`, 0x1e: `\u001e`, 0x1f: `\u001f`,
}

var jsStrReplacementTable = []string{
	0:    `\u0000`,
	'\t': `\t`,
	'\n': `\n`,
	'\v': `\u000b`, // "\v" == "v" on IE 6.
	'\f': `\f`,
	'\r': `\r`,
	// Encode HTML specials as hex so the output can be embedded
	// in HTML attributes without further encoding.
	'"':  `\u0022`,
	'&':  `\u0026`,
	'\'': `\u0027`,
	'+':  `\u002b`,
	'/':  `\/`,
	'<':  `\u003c`,
	'>':  `\u003e`,
	'\\': `\\`,
}

// jsStrNormReplacementTable is like jsStrReplacementTable but does not
// overencode existing escapes since this table has no entry for `\`.
var jsStrNormReplacementTable = []string{
	0:    `\u0000`,
	'\t': `\t`,
	'\n': `\n`,
	'\v': `\u000b`, // "\v" == "v" on IE 6.
	'\f': `\f`,
	'\r': `\r`,
	// Encode HTML specials as hex so the output can be embedded
	// in HTML attributes without further encoding.
	'"':  `\u0022`,
	'&':  `\u0026`,
	'\'': `\u0027`,
	'+':  `\u002b`,
	'/':  `\/`,
	'<':  `\u003c`,
	'>':  `\u003e`,
}
var jsRegexpReplacementTable = []string{
	0:    `\u0000`,
	'\t': `\t`,
	'\n': `\n`,
	'\v': `\u000b`, // "\v" == "v" on IE 6.
	'\f': `\f`,
	'\r': `\r`,
	// Encode HTML specials as hex so the output can be embedded
	// in HTML attributes without further encoding.
	'"':  `\u0022`,
	'$':  `\$`,
	'&':  `\u0026`,
	'\'': `\u0027`,
	'(':  `\(`,
	')':  `\)`,
	'*':  `\*`,
	'+':  `\u002b`,
	'-':  `\-`,
	'.':  `\.`,
	'/':  `\/`,
	'<':  `\u003c`,
	'>':  `\u003e`,
	'?':  `\?`,
	'[':  `\[`,
	'\\': `\\`,
	']':  `\]`,
	'^':  `\^`,
	'{':  `\{`,
	'|':  `\|`,
	'}':  `\}`,
}

// isJSIdentPart reports whether the given rune is a JS identifier part.
// It does not handle all the non-Latin letters, joiners, and combining marks,
// but it does handle every codepoint that can occur in a numeric literal or
// a keyword.
func isJSIdentPart( rune) bool {
	switch {
	case  == '$':
		return true
	case '0' <=  &&  <= '9':
		return true
	case 'A' <=  &&  <= 'Z':
		return true
	case  == '_':
		return true
	case 'a' <=  &&  <= 'z':
		return true
	}
	return false
}

// isJSType reports whether the given MIME type should be considered JavaScript.
//
// It is used to determine whether a script tag with a type attribute is a javascript container.
func isJSType( string) bool {
	// per
	//   https://www.w3.org/TR/html5/scripting-1.html#attr-script-type
	//   https://tools.ietf.org/html/rfc7231#section-3.1.1
	//   https://tools.ietf.org/html/rfc4329#section-3
	//   https://www.ietf.org/rfc/rfc4627.txt
	// discard parameters
	if  := strings.Index(, ";");  >= 0 {
		 = [:]
	}
	 = strings.ToLower()
	 = strings.TrimSpace()
	switch  {
	case
		"application/ecmascript",
		"application/javascript",
		"application/json",
		"application/ld+json",
		"application/x-ecmascript",
		"application/x-javascript",
		"module",
		"text/ecmascript",
		"text/javascript",
		"text/javascript1.0",
		"text/javascript1.1",
		"text/javascript1.2",
		"text/javascript1.3",
		"text/javascript1.4",
		"text/javascript1.5",
		"text/jscript",
		"text/livescript",
		"text/x-ecmascript",
		"text/x-javascript":
		return true
	default:
		return false
	}
}