context.go

// 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 (
	"fmt"
)

// context describes the state an HTML parser must be in when it reaches the
// portion of HTML produced by evaluating a particular template node.
//
// The zero value of type context is the start context for a template that
// produces an HTML fragment as defined at
// http://www.w3.org/TR/html5/syntax.html#the-end
// where the context element is null.
type context struct {
	state   state
	delim   delim
	urlPart urlPart
	jsCtx   jsCtx
	attr    attr
	element element
	err     *Error
}

func (c context) String() string {
	return fmt.Sprintf("{%v %v %v %v %v %v %v}", c.state, c.delim, c.urlPart, c.jsCtx, c.attr, c.element, c.err)
}

// eq reports whether two contexts are equal.
func (c context) eq(d context) bool {
	return c.state == d.state &&
		c.delim == d.delim &&
		c.urlPart == d.urlPart &&
		c.jsCtx == d.jsCtx &&
		c.attr == d.attr &&
		c.element == d.element &&
		c.err == d.err
}

// mangle produces an identifier that includes a suffix that distinguishes it
// from template names mangled with different contexts.
func (c context) mangle(templateName string) string {
	// The mangled name for the default context is the input templateName.
	if c.state == stateText {
		return templateName
	}
	s := templateName + "$htmltemplate_" + c.state.String()
	if c.delim != 0 {
		s += "_" + c.delim.String()
	}
	if c.urlPart != 0 {
		s += "_" + c.urlPart.String()
	}
	if c.jsCtx != 0 {
		s += "_" + c.jsCtx.String()
	}
	if c.attr != 0 {
		s += "_" + c.attr.String()
	}
	if c.element != 0 {
		s += "_" + c.element.String()
	}
	return s
}

// state describes a high-level HTML parser state.
//
// It bounds the top of the element stack, and by extension the HTML insertion
// mode, but also contains state that does not correspond to anything in the
// HTML5 parsing algorithm because a single token production in the HTML
// grammar may contain embedded actions in a template. For instance, the quoted
// HTML attribute produced by
//     <div title="Hello {{.World}}">
// is a single token in HTML's grammar but in a template spans several nodes.
type state uint8

const (
	// stateText is parsed character data. An HTML parser is in
	// this state when its parse position is outside an HTML tag,
	// directive, comment, and special element body.
	stateText state = iota
	// stateTag occurs before an HTML attribute or the end of a tag.
	stateTag
	// stateAttrName occurs inside an attribute name.
	// It occurs between the ^'s in ` ^name^ = value`.
	stateAttrName
	// stateAfterName occurs after an attr name has ended but before any
	// equals sign. It occurs between the ^'s in ` name^ ^= value`.
	stateAfterName
	// stateBeforeValue occurs after the equals sign but before the value.
	// It occurs between the ^'s in ` name =^ ^value`.
	stateBeforeValue
	// stateHTMLCmt occurs inside an <!-- HTML comment -->.
	stateHTMLCmt
	// stateRCDATA occurs inside an RCDATA element (<textarea> or <title>)
	// as described at http://www.w3.org/TR/html5/syntax.html#elements-0
	stateRCDATA
	// stateAttr occurs inside an HTML attribute whose content is text.
	stateAttr
	// stateURL occurs inside an HTML attribute whose content is a URL.
	stateURL
	// stateSrcset occurs inside an HTML srcset attribute.
	stateSrcset
	// stateJS occurs inside an event handler or script element.
	stateJS
	// stateJSDqStr occurs inside a JavaScript double quoted string.
	stateJSDqStr
	// stateJSSqStr occurs inside a JavaScript single quoted string.
	stateJSSqStr
	// stateJSRegexp occurs inside a JavaScript regexp literal.
	stateJSRegexp
	// stateJSBlockCmt occurs inside a JavaScript /* block comment */.
	stateJSBlockCmt
	// stateJSLineCmt occurs inside a JavaScript // line comment.
	stateJSLineCmt
	// stateCSS occurs inside a <style> element or style attribute.
	stateCSS
	// stateCSSDqStr occurs inside a CSS double quoted string.
	stateCSSDqStr
	// stateCSSSqStr occurs inside a CSS single quoted string.
	stateCSSSqStr
	// stateCSSDqURL occurs inside a CSS double quoted url("...").
	stateCSSDqURL
	// stateCSSSqURL occurs inside a CSS single quoted url('...').
	stateCSSSqURL
	// stateCSSURL occurs inside a CSS unquoted url(...).
	stateCSSURL
	// stateCSSBlockCmt occurs inside a CSS /* block comment */.
	stateCSSBlockCmt
	// stateCSSLineCmt occurs inside a CSS // line comment.
	stateCSSLineCmt
	// stateError is an infectious error state outside any valid
	// HTML/CSS/JS construct.
	stateError
)

var stateNames = [...]string{
	stateText:        "stateText",
	stateTag:         "stateTag",
	stateAttrName:    "stateAttrName",
	stateAfterName:   "stateAfterName",
	stateBeforeValue: "stateBeforeValue",
	stateHTMLCmt:     "stateHTMLCmt",
	stateRCDATA:      "stateRCDATA",
	stateAttr:        "stateAttr",
	stateURL:         "stateURL",
	stateSrcset:      "stateSrcset",
	stateJS:          "stateJS",
	stateJSDqStr:     "stateJSDqStr",
	stateJSSqStr:     "stateJSSqStr",
	stateJSRegexp:    "stateJSRegexp",
	stateJSBlockCmt:  "stateJSBlockCmt",
	stateJSLineCmt:   "stateJSLineCmt",
	stateCSS:         "stateCSS",
	stateCSSDqStr:    "stateCSSDqStr",
	stateCSSSqStr:    "stateCSSSqStr",
	stateCSSDqURL:    "stateCSSDqURL",
	stateCSSSqURL:    "stateCSSSqURL",
	stateCSSURL:      "stateCSSURL",
	stateCSSBlockCmt: "stateCSSBlockCmt",
	stateCSSLineCmt:  "stateCSSLineCmt",
	stateError:       "stateError",
}

func (s state) String() string {
	if int(s) < len(stateNames) {
		return stateNames[s]
	}
	return fmt.Sprintf("illegal state %d", int(s))
}

// isComment is true for any state that contains content meant for template
// authors & maintainers, not for end-users or machines.
func isComment(s state) bool {
	switch s {
	case stateHTMLCmt, stateJSBlockCmt, stateJSLineCmt, stateCSSBlockCmt, stateCSSLineCmt:
		return true
	}
	return false
}

// isInTag return whether s occurs solely inside an HTML tag.
func isInTag(s state) bool {
	switch s {
	case stateTag, stateAttrName, stateAfterName, stateBeforeValue, stateAttr:
		return true
	}
	return false
}

// delim is the delimiter that will end the current HTML attribute.
type delim uint8

const (
	// delimNone occurs outside any attribute.
	delimNone delim = iota
	// delimDoubleQuote occurs when a double quote (") closes the attribute.
	delimDoubleQuote
	// delimSingleQuote occurs when a single quote (') closes the attribute.
	delimSingleQuote
	// delimSpaceOrTagEnd occurs when a space or right angle bracket (>)
	// closes the attribute.
	delimSpaceOrTagEnd
)

var delimNames = [...]string{
	delimNone:          "delimNone",
	delimDoubleQuote:   "delimDoubleQuote",
	delimSingleQuote:   "delimSingleQuote",
	delimSpaceOrTagEnd: "delimSpaceOrTagEnd",
}

func (d delim) String() string {
	if int(d) < len(delimNames) {
		return delimNames[d]
	}
	return fmt.Sprintf("illegal delim %d", int(d))
}

// urlPart identifies a part in an RFC 3986 hierarchical URL to allow different
// encoding strategies.
type urlPart uint8

const (
	// urlPartNone occurs when not in a URL, or possibly at the start:
	// ^ in "^http://auth/path?k=v#frag".
	urlPartNone urlPart = iota
	// urlPartPreQuery occurs in the scheme, authority, or path; between the
	// ^s in "h^ttp://auth/path^?k=v#frag".
	urlPartPreQuery
	// urlPartQueryOrFrag occurs in the query portion between the ^s in
	// "http://auth/path?^k=v#frag^".
	urlPartQueryOrFrag
	// urlPartUnknown occurs due to joining of contexts both before and
	// after the query separator.
	urlPartUnknown
)

var urlPartNames = [...]string{
	urlPartNone:        "urlPartNone",
	urlPartPreQuery:    "urlPartPreQuery",
	urlPartQueryOrFrag: "urlPartQueryOrFrag",
	urlPartUnknown:     "urlPartUnknown",
}

func (u urlPart) String() string {
	if int(u) < len(urlPartNames) {
		return urlPartNames[u]
	}
	return fmt.Sprintf("illegal urlPart %d", int(u))
}

// jsCtx determines whether a '/' starts a regular expression literal or a
// division operator.
type jsCtx uint8

const (
	// jsCtxRegexp occurs where a '/' would start a regexp literal.
	jsCtxRegexp jsCtx = iota
	// jsCtxDivOp occurs where a '/' would start a division operator.
	jsCtxDivOp
	// jsCtxUnknown occurs where a '/' is ambiguous due to context joining.
	jsCtxUnknown
)

func (c jsCtx) String() string {
	switch c {
	case jsCtxRegexp:
		return "jsCtxRegexp"
	case jsCtxDivOp:
		return "jsCtxDivOp"
	case jsCtxUnknown:
		return "jsCtxUnknown"
	}
	return fmt.Sprintf("illegal jsCtx %d", int(c))
}

// element identifies the HTML element when inside a start tag or special body.
// Certain HTML element (for example <script> and <style>) have bodies that are
// treated differently from stateText so the element type is necessary to
// transition into the correct context at the end of a tag and to identify the
// end delimiter for the body.
type element uint8

const (
	// elementNone occurs outside a special tag or special element body.
	elementNone element = iota
	// elementScript corresponds to the raw text <script> element
	// with JS MIME type or no type attribute.
	elementScript
	// elementStyle corresponds to the raw text <style> element.
	elementStyle
	// elementTextarea corresponds to the RCDATA <textarea> element.
	elementTextarea
	// elementTitle corresponds to the RCDATA <title> element.
	elementTitle
)

var elementNames = [...]string{
	elementNone:     "elementNone",
	elementScript:   "elementScript",
	elementStyle:    "elementStyle",
	elementTextarea: "elementTextarea",
	elementTitle:    "elementTitle",
}

func (e element) String() string {
	if int(e) < len(elementNames) {
		return elementNames[e]
	}
	return fmt.Sprintf("illegal element %d", int(e))
}

// attr identifies the current HTML attribute when inside the attribute,
// that is, starting from stateAttrName until stateTag/stateText (exclusive).
type attr uint8

const (
	// attrNone corresponds to a normal attribute or no attribute.
	attrNone attr = iota
	// attrScript corresponds to an event handler attribute.
	attrScript
	// attrScriptType corresponds to the type attribute in script HTML element
	attrScriptType
	// attrStyle corresponds to the style attribute whose value is CSS.
	attrStyle
	// attrURL corresponds to an attribute whose value is a URL.
	attrURL
	// attrSrcset corresponds to a srcset attribute.
	attrSrcset
)

var attrNames = [...]string{
	attrNone:       "attrNone",
	attrScript:     "attrScript",
	attrScriptType: "attrScriptType",
	attrStyle:      "attrStyle",
	attrURL:        "attrURL",
	attrSrcset:     "attrSrcset",
}

func (a attr) String() string {
	if int(a) < len(attrNames) {
		return attrNames[a]
	}
	return fmt.Sprintf("illegal attr %d", int(a))
}