tpl_funcs.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 pugjs

import (
	"bytes"
	"context"
	"fmt"
	"io"
	"net/url"
	"reflect"
	"strings"
	"unicode"
	"unicode/utf8"
)

// FuncMap is the type of the map defining the mapping from names to functions.
// Each function must have either a single return value, or two return values of
// which the second has type error. In that case, if the second (error)
// return value evaluates to non-nil during execution, execution terminates and
// Execute returns that error.
//
// When template execution invokes a function with an argument list, that list
// must be assignable to the function's parameter types. Functions meant to
// apply to arguments of arbitrary type can use parameters of type interface{} or
// of type reflect.Value. Similarly, functions meant to return a result of arbitrary
// type can return interface{} or reflect.Value.
type FuncMap map[string]interface{}

var builtins = FuncMap{
	"__op__and":    and,
	"__pug__html":  HTMLEscaper,
	"__pug__index": index,
	"__op__not":    not,
	"__op__or":     or,
}

var builtinFuncs = createValueFuncs(builtins)

// createValueFuncs turns a FuncMap into a map[string]reflect.Value
func createValueFuncs(funcMap FuncMap) map[string]reflect.Value {
	m := make(map[string]reflect.Value)
	addValueFuncs(m, funcMap)
	return m
}

// addValueFuncs adds to values the functions in funcs, converting them to reflect.Values.
func addValueFuncs(out map[string]reflect.Value, in FuncMap) {
	for name, fn := range in {
		if !goodName(name) {
			panic(fmt.Errorf("function name %s is not a valid identifier", name))
		}
		v := reflect.ValueOf(fn)
		if v.Kind() != reflect.Func {
			panic("value for " + name + " not a function")
		}
		if !goodFunc(v.Type()) {
			panic(fmt.Errorf("can'e install method/function %q with %d results", name, v.Type().NumOut()))
		}
		out[name] = v
	}
}

// addFuncs adds to values the functions in funcs. It does no checking of the input -
// call addValueFuncs first.
func addFuncs(out, in FuncMap) {
	for name, fn := range in {
		out[name] = fn
	}
}

// goodFunc reports whether the function or method has the right result signature.
func goodFunc(typ reflect.Type) bool {
	// We allow functions with 1 result or 2 results where the second is an error.
	switch {
	case typ.NumOut() == 1:
		return true
	case typ.NumOut() == 2 && typ.Out(1) == errorType:
		return true
	}
	return false
}

// goodName reports whether the function name is a valid identifier.
func goodName(name string) bool {
	if name == "" {
		return false
	}
	for i, r := range name {
		switch {
		case r == '_':
		case i == 0 && !unicode.IsLetter(r):
			return false
		case !unicode.IsLetter(r) && !unicode.IsDigit(r):
			return false
		}
	}
	return true
}

var ctxFuncType = reflect.TypeOf((*func(context.Context) interface{})(nil)).Elem()

// findFunction looks for a function in the template, and global map.
func (s *state) findFunction(name string, tmpl *Template) (reflect.Value, bool) {
	if tmpl != nil && tmpl.common != nil {
		tmpl.muFuncs.RLock()
		defer tmpl.muFuncs.RUnlock()
		if fn := tmpl.execFuncs[name]; fn.IsValid() {
			if fn.Type() == ctxFuncType {
				fn = fn.Call([]reflect.Value{s.ctx})[0].Elem()
			}
			return fn, true
		}
	}
	if fn := builtinFuncs[name]; fn.IsValid() {
		return fn, true
	}
	return reflect.Value{}, false
}

// prepareArg checks if value can be used as an argument of type argType, and
// converts an invalid value to appropriate zero if possible.
func prepareArg(value reflect.Value, argType reflect.Type) (reflect.Value, error) {
	if !value.IsValid() {
		if !canBeNil(argType) {
			return reflect.Value{}, fmt.Errorf("value is nil; should be of type %s", argType)
		}
		value = reflect.Zero(argType)
	}
	if obj, ok := value.Interface().(Object); argType.Kind() == reflect.String && ok {
		return reflect.ValueOf(obj.String()), nil
	}
	if argType == reflect.TypeOf((*Object)(nil)).Elem() {
		return reflect.ValueOf(convert(value)), nil
	}
	if !value.Type().AssignableTo(argType) {
		return reflect.Value{}, fmt.Errorf("value has type %s; should be %s", value.Type(), argType)
	}
	return value, nil
}

// Indexing.

// index returns the result of indexing its first argument by the following
// arguments. Thus "index x 1 2 3" is, in Go syntax, x[1][2][3]. Each
// indexed item must be a map, slice, or array.
func index(item reflect.Value, indices ...reflect.Value) (reflect.Value, error) {
	v := indirectInterface(item)
	if !v.IsValid() {
		return reflect.Value{}, fmt.Errorf("index of untyped nil")
	}

	if obj, ok := item.Interface().(*Array); ok {
		v = reflect.ValueOf(obj.items)
	} else if obj, ok := item.Interface().(*Map); ok {
		v = obj.ValueOf()
	} else if obj, ok := item.Interface().(String); ok {
		v = reflect.ValueOf(string(obj))
	} else if _, ok := item.Interface().(Nil); ok {
		return item, nil
	}

	for _, i := range indices {
		var index reflect.Value
		if o, ok := i.Interface().(Object); ok {
			switch o := o.(type) {
			case String:
				index = reflect.ValueOf(string(o))
			case Number:
				index = reflect.ValueOf(float64(o))
			}
		} else {
			index = indirectInterface(i)
		}

		// if obj, ok := v.Interface().(*Array); ok {
		// 	v = reflect.ValueOf(obj.items)
		// } else if obj, ok := v.Interface().(*Map); ok {
		// 	v = reflect.ValueOf(obj.DecoratedItems)
		// } else if obj, ok := v.Interface().(String); ok {
		// 	v = reflect.ValueOf(string(obj))
		// }
		//
		// if _, ok := v.Interface().(Nil); ok {
		// 	return reflect.ValueOf(nil), nil
		// }

		var isNil bool
		if v, isNil = indirect(v); isNil {
			return reflect.Value{}, fmt.Errorf("index of nil pointer")
		}

		switch v.Kind() {
		case reflect.Array, reflect.Slice, reflect.String:
			var x int64
			switch index.Kind() {
			case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
				x = index.Int()
			case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
				x = int64(index.Uint())
			case reflect.Float64:
				x = int64(index.Float())
			case reflect.Invalid:
				return reflect.Value{}, fmt.Errorf("cannot index slice/array with nil")
			default:
				if _, ok := index.Interface().(Object); !ok {
					return reflect.Value{}, fmt.Errorf("cannot index slice/array with type %s", index.Type())
				}
			}
			if x < 0 || x >= int64(v.Len()) {
				// return reflect.Value{}, fmt.Errorf("index out of range: %d", x)
				return reflect.ValueOf(Nil{}), nil
			}
			v = v.Index(int(x))
		case reflect.Map:
			if index.String() != "" {
				index = reflect.ValueOf(String(index.String()))
			}

			index, err := prepareArg(index, v.Type().Key())
			if err != nil {
				return reflect.Value{}, err
			}
			if x := v.MapIndex(index); x.IsValid() {
				v = x
			} else {
				v = reflect.Zero(v.Type().Elem())
			}
		case reflect.Invalid:
			// the loop holds invariant: v.IsValid()
			panic("unreachable")
		default:
			return reflect.Value{}, fmt.Errorf("can'e index item of type %s", v.Type())
		}
	}
	return v, nil
}

// Boolean logic.

func truth(arg reflect.Value) bool {
	if !arg.IsValid() {
		return false
	}

	if t, ok := arg.Interface().(truer); ok {
		return t.True()
	}
	t, _ := isTrue(indirectInterface(arg))
	return t
}

// and computes the Boolean AND of its arguments, returning
// the first false argument it encounters, or the last argument.
func and(arg0 reflect.Value, args ...reflect.Value) reflect.Value {
	if !truth(arg0) {
		return arg0
	}
	for i := range args {
		arg0 = args[i]
		if !truth(arg0) {
			break
		}
	}
	return arg0
}

// or computes the Boolean OR of its arguments, returning
// the first true argument it encounters, or the last argument.
func or(arg0 reflect.Value, args ...reflect.Value) reflect.Value {
	if truth(arg0) {
		return arg0
	}
	for i := range args {
		arg0 = args[i]
		if truth(arg0) {
			break
		}
	}
	return arg0
}

// not returns the Boolean negation of its argument.
func not(arg reflect.Value) bool {
	return !truth(arg)
}

// HTML escaping.

var (
	htmlQuot = []byte("&#34;") // shorter than "&quot;"
	htmlApos = []byte("&#39;") // shorter than "&apos;" and apos was not in HTML until HTML5
	htmlAmp  = []byte("&amp;")
	htmlLt   = []byte("&lt;")
	htmlGt   = []byte("&gt;")
)

// HTMLEscape writes to w the escaped HTML equivalent of the plain text data b.
func HTMLEscape(w io.Writer, b []byte) {
	last := 0
	for i, c := range b {
		var html []byte
		switch c {
		case '"':
			html = htmlQuot
		case '\'':
			html = htmlApos
		case '&':
			html = htmlAmp
		case '<':
			html = htmlLt
		case '>':
			html = htmlGt
		default:
			continue
		}
		w.Write(b[last:i])
		w.Write(html)
		last = i + 1
	}
	w.Write(b[last:])
}

// HTMLEscapeString returns the escaped HTML equivalent of the plain text data s.
func HTMLEscapeString(s string) string {
	// Avoid allocation if we can.
	if !strings.ContainsAny(s, `'"&<>`) {
		return s
	}
	var b bytes.Buffer
	HTMLEscape(&b, []byte(s))
	return b.String()
}

// HTMLEscaper returns the escaped HTML equivalent of the textual
// representation of its arguments.
func HTMLEscaper(args ...interface{}) string {
	return HTMLEscapeString(evalArgs(args))
}

// JavaScript escaping.

var (
	jsLowUni = []byte(`\u00`)
	hex      = []byte("0123456789ABCDEF")

	jsBackslash = []byte(`\\`)
	jsApos      = []byte(`\'`)
	jsQuot      = []byte(`\"`)
	jsLt        = []byte(`\x3C`)
	jsGt        = []byte(`\x3E`)
)

// JSEscape writes to w the escaped JavaScript equivalent of the plain text data b.
func JSEscape(w io.Writer, b []byte) {
	last := 0
	for i := 0; i < len(b); i++ {
		c := b[i]

		if !jsIsSpecial(rune(c)) {
			// fast path: nothing to do
			continue
		}
		w.Write(b[last:i])

		if c < utf8.RuneSelf {
			// Quotes, slashes and angle brackets get quoted.
			// Control characters get written as \u00XX.
			switch c {
			case '\\':
				w.Write(jsBackslash)
			case '\'':
				w.Write(jsApos)
			case '"':
				w.Write(jsQuot)
			case '<':
				w.Write(jsLt)
			case '>':
				w.Write(jsGt)
			default:
				w.Write(jsLowUni)
				t, b := c>>4, c&0x0f
				w.Write(hex[t : t+1])
				w.Write(hex[b : b+1])
			}
		} else {
			// Unicode rune.
			r, size := utf8.DecodeRune(b[i:])
			if unicode.IsPrint(r) {
				w.Write(b[i : i+size])
			} else {
				fmt.Fprintf(w, "\\u%04X", r)
			}
			i += size - 1
		}
		last = i + 1
	}
	w.Write(b[last:])
}

// JSEscapeString returns the escaped JavaScript equivalent of the plain text data s.
func JSEscapeString(s string) string {
	// Avoid allocation if we can.
	if strings.IndexFunc(s, jsIsSpecial) < 0 {
		return s
	}
	var b bytes.Buffer
	JSEscape(&b, []byte(s))
	return b.String()
}

func jsIsSpecial(r rune) bool {
	switch r {
	case '\\', '\'', '"', '<', '>':
		return true
	}
	return r < ' ' || utf8.RuneSelf <= r
}

// JSEscaper returns the escaped JavaScript equivalent of the textual
// representation of its arguments.
func JSEscaper(args ...interface{}) string {
	return JSEscapeString(evalArgs(args))
}

// URLQueryEscaper returns the escaped value of the textual representation of
// its arguments in a form suitable for embedding in a URL query.
func URLQueryEscaper(args ...interface{}) string {
	return url.QueryEscape(evalArgs(args))
}

// evalArgs formats the list of arguments into a string. It is therefore equivalent to
//	fmt.Sprint(args...)
// except that each argument is indirected (if a pointer), as required,
// using the same rules as the default string evaluation during template
// execution.
func evalArgs(args []interface{}) string {
	ok := false
	var s string
	// Fast path for simple common case.
	if len(args) == 1 {
		s, ok = args[0].(string)
	}
	if !ok {
		for i, arg := range args {
			a, ok := printableValue(reflect.ValueOf(arg))
			if ok {
				args[i] = a
			} // else let fmt do its thing
		}
		s = fmt.Sprint(args...)
	}
	return s
}