package template

import (
	"bytes"
	"fmt"
	"html"
	"io"
	"text/template"
	"text/template/parse"
)

func escapeTemplate(tmpl *Template, node parse.Node, name string) error {
	c, _ := tmpl.esc.escapeTree(context{}, node, name, 0)
	var err error
	if c.err != nil {
		err, c.err.Name = c.err, name
	} else if c.state != stateText {
		err = &Error{ErrEndContext, nil, name, 0, fmt.Sprintf("ends in a non-text context: %v", c)}
	}

		if t := tmpl.set[name]; t != nil {
			t.escapeErr = err
			t.text.Tree = nil
			t.Tree = nil
		}
		return err
	}
	tmpl.esc.commit()
	if t := tmpl.set[name]; t != nil {
		t.escapeErr = escapeOK
		t.Tree = t.text.Tree
	}
	return nil
}

	if len(args) == 1 {
		if s, ok := args[0].(string); ok {
			return s
		}
	}
	for i, arg := range args {
		args[i] = indirectToStringerOrError(arg)
	}
	return fmt.Sprint(args...)
}

var funcMap = template.FuncMap{
	"_html_template_attrescaper":     attrEscaper,
	"_html_template_commentescaper":  commentEscaper,
	"_html_template_cssescaper":      cssEscaper,
	"_html_template_cssvaluefilter":  cssValueFilter,
	"_html_template_htmlnamefilter":  htmlNameFilter,
	"_html_template_htmlescaper":     htmlEscaper,
	"_html_template_jsregexpescaper": jsRegexpEscaper,
	"_html_template_jsstrescaper":    jsStrEscaper,
	"_html_template_jsvalescaper":    jsValEscaper,
	"_html_template_nospaceescaper":  htmlNospaceEscaper,
	"_html_template_rcdataescaper":   rcdataEscaper,
	"_html_template_srcsetescaper":   srcsetFilterAndEscaper,
	"_html_template_urlescaper":      urlEscaper,
	"_html_template_urlfilter":       urlFilter,
	"_html_template_urlnormalizer":   urlNormalizer,
	"_eval_args_":                    evalArgs,
}

	actionNodeEdits   map[*parse.ActionNode][]string
	templateNodeEdits map[*parse.TemplateNode]string
	textNodeEdits     map[*parse.TextNode][]byte
}

func makeEscaper(n *nameSpace) escaper {
	return escaper{
		n,
		map[string]context{},
		map[string]*template.Template{},
		map[string]bool{},
		map[*parse.ActionNode][]string{},
		map[*parse.TemplateNode]string{},
		map[*parse.TextNode][]byte{},
	}
}

const filterFailsafe = "ZgotmplZ"

func (e *escaper) escape(c context, n parse.Node) context {
	switch n := n.(type) {
	case *parse.ActionNode:
		return e.escapeAction(c, n)
	case *parse.CommentNode:
		return c
	case *parse.IfNode:
		return e.escapeBranch(c, &n.BranchNode, "if")
	case *parse.ListNode:
		return e.escapeList(c, n)
	case *parse.RangeNode:
		return e.escapeBranch(c, &n.BranchNode, "range")
	case *parse.TemplateNode:
		return e.escapeTemplate(c, n)
	case *parse.TextNode:
		return e.escapeText(c, n)
	case *parse.WithNode:
		return e.escapeBranch(c, &n.BranchNode, "with")
	}
	panic("escaping " + n.String() + " is unimplemented")
}

func (e *escaper) escapeAction(c context, n *parse.ActionNode) context {

		return c
	}

	for pos, idNode := range n.Pipe.Cmds {
		node, ok := idNode.Args[0].(*parse.IdentifierNode)

			continue
		}
		ident := node.Ident
		if _, ok := predefinedEscapers[ident]; ok {
			if pos < len(n.Pipe.Cmds)-1 ||
				c.state == stateAttr && c.delim == delimSpaceOrTagEnd && ident == "html" {
				return context{
					state: stateError,
					err:   errorf(ErrPredefinedEscaper, n, n.Line, "predefined escaper %q disallowed in template", ident),
				}
			}
		}
	}
	s := make([]string, 0, 3)
	switch c.state {
	case stateError:
		return c
	case stateURL, stateCSSDqStr, stateCSSSqStr, stateCSSDqURL, stateCSSSqURL, stateCSSURL:
		switch c.urlPart {
		case urlPartNone:
			s = append(s, "_html_template_urlfilter")
			fallthrough
		case urlPartPreQuery:
			switch c.state {
			case stateCSSDqStr, stateCSSSqStr:
				s = append(s, "_html_template_cssescaper")
			default:
				s = append(s, "_html_template_urlnormalizer")
			}
		case urlPartQueryOrFrag:
			s = append(s, "_html_template_urlescaper")
		case urlPartUnknown:
			return context{
				state: stateError,
				err:   errorf(ErrAmbigContext, n, n.Line, "%s appears in an ambiguous context within a URL", n),
			}
		default:
			panic(c.urlPart.String())
		}
	case stateJS:

		c.jsCtx = jsCtxDivOp
	case stateJSDqStr, stateJSSqStr:
		s = append(s, "_html_template_jsstrescaper")
	case stateJSRegexp:
		s = append(s, "_html_template_jsregexpescaper")
	case stateCSS:
		s = append(s, "_html_template_cssvaluefilter")
	case stateText:
		s = append(s, "_html_template_htmlescaper")
	case stateRCDATA:
		s = append(s, "_html_template_rcdataescaper")

	case stateAttrName, stateTag:
		c.state = stateAttrName
		s = append(s, "_html_template_htmlnamefilter")
	case stateSrcset:
		s = append(s, "_html_template_srcsetescaper")
	default:
		if isComment(c.state) {
			s = append(s, "_html_template_commentescaper")
		} else {
			panic("unexpected state " + c.state.String())
		}
	}
	switch c.delim {

	case delimSpaceOrTagEnd:
		s = append(s, "_html_template_nospaceescaper")
	default:
		s = append(s, "_html_template_attrescaper")
	}
	e.editActionNode(n, s)
	return c
}

func ensurePipelineContains(p *parse.PipeNode, s []string) {

		return

	pipelineLen := len(p.Cmds)
	if pipelineLen > 0 {
		lastCmd := p.Cmds[pipelineLen-1]
		if idNode, ok := lastCmd.Args[0].(*parse.IdentifierNode); ok {

					lastCmd.Args[0] = parse.NewIdentifier("_eval_args_").SetTree(nil).SetPos(lastCmd.Args[0].Position())
					p.Cmds = appendCmd(p.Cmds, newIdentCmd(esc, p.Position()))
					pipelineLen++

				dup := false
				for i, escaper := range s {
					if escFnsEq(esc, escaper) {
						s[i] = idNode.Ident
						dup = true
					}
				}

					pipelineLen--
				}
			}
		}

	newCmds := make([]*parse.CommandNode, pipelineLen, pipelineLen+len(s))
	insertedIdents := make(map[string]bool)
	for i := 0; i < pipelineLen; i++ {
		cmd := p.Cmds[i]
		newCmds[i] = cmd
		if idNode, ok := cmd.Args[0].(*parse.IdentifierNode); ok {
			insertedIdents[normalizeEscFn(idNode.Ident)] = true
		}
	}
	for _, name := range s {

			newCmds = appendCmd(newCmds, newIdentCmd(name, p.Position()))
		}
	}
	p.Cmds = newCmds
}

var predefinedEscapers = map[string]bool{
	"html":     true,
	"urlquery": true,
}

	"_html_template_attrescaper":   "html",
	"_html_template_htmlescaper":   "html",

	"_html_template_urlnormalizer": "urlquery",
}

func escFnsEq(a, b string) bool {
	return normalizeEscFn(a) == normalizeEscFn(b)
}

func normalizeEscFn(e string) string {
	if norm := equivEscapers[e]; norm != "" {
		return norm
	}
	return e
}

var redundantFuncs = map[string]map[string]bool{
	"_html_template_commentescaper": {
		"_html_template_attrescaper":    true,
		"_html_template_nospaceescaper": true,
		"_html_template_htmlescaper":    true,
	},
	"_html_template_cssescaper": {
		"_html_template_attrescaper": true,
	},
	"_html_template_jsregexpescaper": {
		"_html_template_attrescaper": true,
	},
	"_html_template_jsstrescaper": {
		"_html_template_attrescaper": true,
	},
	"_html_template_urlescaper": {
		"_html_template_urlnormalizer": true,
	},
}

func appendCmd(cmds []*parse.CommandNode, cmd *parse.CommandNode) []*parse.CommandNode {
	if n := len(cmds); n != 0 {
		last, okLast := cmds[n-1].Args[0].(*parse.IdentifierNode)
		next, okNext := cmd.Args[0].(*parse.IdentifierNode)
		if okLast && okNext && redundantFuncs[last.Ident][next.Ident] {
			return cmds
		}
	}
	return append(cmds, cmd)
}

func newIdentCmd(identifier string, pos parse.Pos) *parse.CommandNode {
	return &parse.CommandNode{
		NodeType: parse.NodeCommand,
		Args:     []parse.Node{parse.NewIdentifier(identifier).SetTree(nil).SetPos(pos)}, // TODO: SetTree.
	}
}

func nudge(c context) context {
	switch c.state {

		c.state = stateAttrName

		c.state, c.delim, c.attr = attrStartStates[c.attr], delimSpaceOrTagEnd, attrNone

		c.state, c.attr = stateAttrName, attrNone
	}
	return c
}

func join(a, b context, node parse.Node, nodeName string) context {
	if a.state == stateError {
		return a
	}
	if b.state == stateError {
		return b
	}
	if a.eq(b) {
		return a
	}

	c := a
	c.urlPart = b.urlPart

		c.urlPart = urlPartUnknown
		return c
	}

	c = a
	c.jsCtx = b.jsCtx

		c.jsCtx = jsCtxUnknown
		return c
	}

	if c, d := nudge(a), nudge(b); !(c.eq(a) && d.eq(b)) {
		if e := join(c, d, node, nodeName); e.state != stateError {
			return e
		}
	}

	return context{
		state: stateError,
		err:   errorf(ErrBranchEnd, node, 0, "{{%s}} branches end in different contexts: %v, %v", nodeName, a, b),
	}
}

func (e *escaper) escapeBranch(c context, n *parse.BranchNode, nodeName string) context {
	c0 := e.escapeList(c, n.List)

		c1, _ := e.escapeListConditionally(c0, n.List, nil)
		c0 = join(c0, c1, n, nodeName)

			c0.err.Line = n.Line
			c0.err.Description = "on range loop re-entry: " + c0.err.Description
			return c0
		}
	}
	c1 := e.escapeList(c, n.ElseList)
	return join(c0, c1, n, nodeName)
}

func (e *escaper) escapeList(c context, n *parse.ListNode) context {
	if n == nil {
		return c
	}
	for _, m := range n.Nodes {
		c = e.escape(c, m)
	}
	return c
}

func (e *escaper) escapeListConditionally(c context, n *parse.ListNode, filter func(*escaper, context) bool) (context, bool) {

	for k, v := range e.output {
		e1.output[k] = v
	}
	c = e1.escapeList(c, n)
	ok := filter != nil && filter(&e1, c)

		for k, v := range e1.output {
			e.output[k] = v
		}
		for k, v := range e1.derived {
			e.derived[k] = v
		}
		for k, v := range e1.called {
			e.called[k] = v
		}
		for k, v := range e1.actionNodeEdits {
			e.editActionNode(k, v)
		}
		for k, v := range e1.templateNodeEdits {
			e.editTemplateNode(k, v)
		}
		for k, v := range e1.textNodeEdits {
			e.editTextNode(k, v)
		}
	}
	return c, ok
}

func (e *escaper) escapeTemplate(c context, n *parse.TemplateNode) context {
	c, name := e.escapeTree(c, n, n.Name, n.Line)
	if name != n.Name {
		e.editTemplateNode(n, name)
	}
	return c
}

	dname := c.mangle(name)
	e.called[dname] = true

		return out, dname
	}
	t := e.template(name)

		if e.ns.set[name] != nil {
			return context{
				state: stateError,
				err:   errorf(ErrNoSuchTemplate, node, line, "%q is an incomplete or empty template", name),
			}, dname
		}
		return context{
			state: stateError,
			err:   errorf(ErrNoSuchTemplate, node, line, "no such template %q", name),
		}, dname
	}

		dt := e.template(dname)
		if dt == nil {
			dt = template.New(dname)
			dt.Tree = &parse.Tree{Name: dname, Root: t.Root.CopyList()}
			e.derived[dname] = dt
		}
		t = dt
	}
	return e.computeOutCtx(c, t), dname
}

	c1, ok := e.escapeTemplateBody(c, t)

		if c2, ok2 := e.escapeTemplateBody(c1, t); ok2 {
			c1, ok = c2, true

	}
	if !ok && c1.state != stateError {
		return context{
			state: stateError,
			err:   errorf(ErrOutputContext, t.Tree.Root, 0, "cannot compute output context for template %s", t.Name()),
		}
	}
	return c1
}

func (e *escaper) escapeTemplateBody(c context, t *template.Template) (context, bool) {
	filter := func(e1 *escaper, c1 context) bool {

			return false
		}

			return true

		return c.eq(c1)

	e.output[t.Name()] = c
	return e.escapeListConditionally(c, t.Tree.Root, filter)
}

var delimEnds = [...]string{
	delimDoubleQuote: `"`,

	delimSpaceOrTagEnd: " \t\n\f\r>",
}

var doctypeBytes = []byte("<!DOCTYPE")

func (e *escaper) escapeText(c context, n *parse.TextNode) context {
	s, written, i, b := n.Text, 0, 0, new(bytes.Buffer)
	for i != len(s) {
		c1, nread := contextAfterText(c, s[i:])
		i1 := i + nread
		if c.state == stateText || c.state == stateRCDATA {
			end := i1
			if c1.state != c.state {
				for j := end - 1; j >= i; j-- {
					if s[j] == '<' {
						end = j
						break
					}
				}
			}
			for j := i; j < end; j++ {
				if s[j] == '<' && !bytes.HasPrefix(bytes.ToUpper(s[j:]), doctypeBytes) {
					b.Write(s[written:j])
					b.WriteString("&lt;")
					written = j + 1
				}
			}
		} else if isComment(c.state) && c.delim == delimNone {
			switch c.state {

				if bytes.ContainsAny(s[written:i1], "\n\r\u2028\u2029") {
					b.WriteByte('\n')
				} else {
					b.WriteByte(' ')
				}
			case stateCSSBlockCmt:
				b.WriteByte(' ')
			}
			written = i1
		}

			cs := i1 - 2

				cs -= 2
			}
			b.Write(s[written:cs])
			written = i1
		}
		if i == i1 && c.state == c1.state {
			panic(fmt.Sprintf("infinite loop from %v to %v on %q..%q", c, c1, s[:i], s[i:]))
		}
		c, i = c1, i1
	}

	if written != 0 && c.state != stateError {
		if !isComment(c.state) || c.delim != delimNone {
			b.Write(n.Text[written:])
		}
		e.editTextNode(n, b.Bytes())
	}
	return c
}

func contextAfterText(c context, s []byte) (context, int) {
	if c.delim == delimNone {
		c1, i := tSpecialTagEnd(c, s)

			return c1, 0

		return transitionFunc[c.state](c, s[:i])
	}

	i := bytes.IndexAny(s, delimEnds[c.delim])
	if i == -1 {
		i = len(s)
	}

		if j := bytes.IndexAny(s[:i], "\"'<=`"); j >= 0 {
			return context{
				state: stateError,
				err:   errorf(ErrBadHTML, nil, 0, "%q in unquoted attr: %q", s[j:j+1], s[:i]),
			}, len(s)
		}
	}

		for u := []byte(html.UnescapeString(string(s))); len(u) != 0; {
			c1, i1 := transitionFunc[c.state](c, u)
			c, u = c1, u[i1:]
		}
		return c, len(s)
	}

	element := c.element

	if c.state == stateAttr && c.element == elementScript && c.attr == attrScriptType && !isJSType(string(s[:i])) {
		element = elementNone
	}

		i++

	return context{state: stateTag, element: element}, i
}

func (e *escaper) editActionNode(n *parse.ActionNode, cmds []string) {
	if _, ok := e.actionNodeEdits[n]; ok {
		panic(fmt.Sprintf("node %s shared between templates", n))
	}
	e.actionNodeEdits[n] = cmds
}

func (e *escaper) editTemplateNode(n *parse.TemplateNode, callee string) {
	if _, ok := e.templateNodeEdits[n]; ok {
		panic(fmt.Sprintf("node %s shared between templates", n))
	}
	e.templateNodeEdits[n] = callee
}

func (e *escaper) editTextNode(n *parse.TextNode, text []byte) {
	if _, ok := e.textNodeEdits[n]; ok {
		panic(fmt.Sprintf("node %s shared between templates", n))
	}
	e.textNodeEdits[n] = text
}

func (e *escaper) commit() {
	for name := range e.output {
		e.template(name).Funcs(funcMap)

	tmpl := e.arbitraryTemplate()
	for _, t := range e.derived {
		if _, err := tmpl.text.AddParseTree(t.Name(), t.Tree); err != nil {
			panic("error adding derived template")
		}
	}
	for n, s := range e.actionNodeEdits {
		ensurePipelineContains(n.Pipe, s)
	}
	for n, name := range e.templateNodeEdits {
		n.Name = name
	}
	for n, s := range e.textNodeEdits {
		n.Text = s

	e.called = make(map[string]bool)
	e.actionNodeEdits = make(map[*parse.ActionNode][]string)
	e.templateNodeEdits = make(map[*parse.TemplateNode]string)
	e.textNodeEdits = make(map[*parse.TextNode][]byte)
}

	t := e.arbitraryTemplate().text.Lookup(name)
	if t == nil {
		t = e.derived[name]
	}
	return t
}

func (e *escaper) arbitraryTemplate() *Template {
	for _, t := range e.ns.set {
		return t
	}
	panic("no templates in name space")
}

func HTMLEscape(w io.Writer, b []byte) {
	template.HTMLEscape(w, b)
}

func HTMLEscapeString(s string) string {
	return template.HTMLEscapeString(s)
}

func HTMLEscaper(args ...interface{}) string {
	return template.HTMLEscaper(args...)
}

func JSEscape(w io.Writer, b []byte) {
	template.JSEscape(w, b)
}

func JSEscapeString(s string) string {
	return template.JSEscapeString(s)
}

func JSEscaper(args ...interface{}) string {
	return template.JSEscaper(args...)
}

func URLQueryEscaper(args ...interface{}) string {
	return template.URLQueryEscaper(args...)