// Copyright 2014 Manu Martinez-Almeida.  All rights reserved.
// Use of this source code is governed by a MIT style
// license that can be found in the LICENSE file.

package gin

import (
	"encoding/xml"
	"net/http"
	"os"
	"path"
	"reflect"
	"runtime"
	"strconv"
	"strings"
)

// BindKey indicates a default bind key.
const BindKey = "_gin-gonic/gin/bindkey"

// Bind is a helper function for given interface object and returns a Gin middleware.
func Bind(val interface{}) HandlerFunc {
	value := reflect.ValueOf(val)
	if value.Kind() == reflect.Ptr {
		panic(`Bind struct can not be a pointer. Example:
	Use: gin.Bind(Struct{}) instead of gin.Bind(&Struct{})
`)
	}
	typ := value.Type()

	return func(c *Context) {
		obj := reflect.New(typ).Interface()
		if c.Bind(obj) == nil {
			c.Set(BindKey, obj)
		}
	}
}

// WrapF is a helper function for wrapping http.HandlerFunc and returns a Gin middleware.
func WrapF(f http.HandlerFunc) HandlerFunc {
	return func(c *Context) {
		f(c.Writer, c.Request)
	}
}

// WrapH is a helper function for wrapping http.Handler and returns a Gin middleware.
func WrapH(h http.Handler) HandlerFunc {
	return func(c *Context) {
		h.ServeHTTP(c.Writer, c.Request)
	}
}

// H is a shortcut for map[string]interface{}
type H map[string]interface{}

// MarshalXML allows type H to be used with xml.Marshal.
func (h H) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
	start.Name = xml.Name{
		Space: "",
		Local: "map",
	}
	if err := e.EncodeToken(start); err != nil {
		return err
	}
	for key, value := range h {
		elem := xml.StartElement{
			Name: xml.Name{Space: "", Local: key},
			Attr: []xml.Attr{},
		}
		if err := e.EncodeElement(value, elem); err != nil {
			return err
		}
	}

	return e.EncodeToken(xml.EndElement{Name: start.Name})
}

func assert1(guard bool, text string) {
	if !guard {
		panic(text)
	}
}

func filterFlags(content string) string {
	for i, char := range content {
		if char == ' ' || char == ';' {
			return content[:i]
		}
	}
	return content
}

func chooseData(custom, wildcard interface{}) interface{} {
	if custom == nil {
		if wildcard == nil {
			panic("negotiation config is invalid")
		}
		return wildcard
	}
	return custom
}

func parseAccept(acceptHeader string) []string {
	parts := strings.Split(acceptHeader, ",")
	out := make([]string, 0, len(parts))
	for _, part := range parts {
		if part = strings.TrimSpace(strings.Split(part, ";")[0]); part != "" {
			out = append(out, part)
		}
	}
	return out
}

func lastChar(str string) uint8 {
	if str == "" {
		panic("The length of the string can't be 0")
	}
	return str[len(str)-1]
}

func nameOfFunction(f interface{}) string {
	return runtime.FuncForPC(reflect.ValueOf(f).Pointer()).Name()
}

func joinPaths(absolutePath, relativePath string) string {
	if relativePath == "" {
		return absolutePath
	}

	finalPath := path.Join(absolutePath, relativePath)
	appendSlash := lastChar(relativePath) == '/' && lastChar(finalPath) != '/'
	if appendSlash {
		return finalPath + "/"
	}
	return finalPath
}

func resolveAddress(addr []string) string {
	switch len(addr) {
	case 0:
		if port := os.Getenv("PORT"); port != "" {
			if isValidPORTEnvVar(port) {
				debugPrint("Environment variable PORT=\"%s\"", port)
				return ":" + port
			}
		}
		debugPrint("Environment variable PORT is undefined or invalid. Using port :8080 by default")
		return ":8080"
	case 1:
		return addr[0]
	default:
		panic("too many parameters")
	}
}

// Determine the PORT environment variable whether is valid。
// If the PORT can be parsed to uint(0-65535)，return true。
func isValidPORTEnvVar(portString string) bool {
	_, err := strconv.ParseUint(portString, 10, 16)
	return err == nil
}