// Copyright 2014 The Macaron Authors
//
// Licensed under the Apache License, Version 2.0 (the "License"): you may
// not use this file except in compliance with the License. You may obtain
// a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations
// under the License.

package web

import (
	"encoding/json"
	"errors"
	"fmt"
	"html/template"
	"net"
	"net/http"
	"net/url"
	"strconv"
	"strings"
	"syscall"

	"github.com/grafana/grafana/pkg/util/errutil"
	"github.com/grafana/grafana/pkg/util/errutil/errhttp"
)

// Context represents the runtime context of current request of Macaron instance.
// It is the integration of most frequently used middlewares and helper methods.
type Context struct {
	mws []Middleware

	Req      *http.Request
	Resp     ResponseWriter
	template *template.Template
}

var errMissingWrite = errutil.NewBase(errutil.StatusInternal, "web.missingWrite")

func (ctx *Context) run() {
	h := http.Handler(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {}))
	for i := len(ctx.mws) - 1; i >= 0; i-- {
		h = ctx.mws[i](h)
	}

	rw := ctx.Resp
	h.ServeHTTP(ctx.Resp, ctx.Req)

	// Prevent the handler chain from not writing anything.
	// This indicates nearly always that a middleware is misbehaving and not calling its next.ServeHTTP().
	// In rare cases where a blank http.StatusOK without any body is wished, explicitly state that using w.WriteStatus(http.StatusOK)
	if !rw.Written() {
		errhttp.Write(
			ctx.Req.Context(),
			errMissingWrite.Errorf("chain did not write HTTP response: %s", ctx.Req.URL.Path),
			rw,
		)
	}
}

// RemoteAddr returns more real IP address.
func (ctx *Context) RemoteAddr() string {
	return RemoteAddr(ctx.Req)
}

func RemoteAddr(req *http.Request) string {
	addr := req.Header.Get("X-Real-IP")

	if len(addr) == 0 {
		// X-Forwarded-For may contain multiple IP addresses, separated by
		// commas.
		addr = strings.TrimSpace(strings.Split(req.Header.Get("X-Forwarded-For"), ",")[0])
	}

	// parse user inputs from headers to prevent log forgery
	if len(addr) > 0 {
		if parsedIP := net.ParseIP(addr); parsedIP == nil {
			// if parsedIP is nil we clean addr and populate with RemoteAddr below
			addr = ""
		}
	}

	if len(addr) == 0 {
		addr = req.RemoteAddr
		if i := strings.LastIndex(addr, ":"); i > -1 {
			addr = addr[:i]
		}
	}

	return addr
}

const (
	headerContentType = "Content-Type"
	contentTypeJSON   = "application/json; charset=UTF-8"
	contentTypeHTML   = "text/html; charset=UTF-8"
)

// HTML renders the HTML with default template set.
func (ctx *Context) HTML(status int, name string, data interface{}) {
	ctx.Resp.Header().Set(headerContentType, contentTypeHTML)
	ctx.Resp.WriteHeader(status)
	if err := ctx.template.ExecuteTemplate(ctx.Resp, name, data); err != nil {
		if errors.Is(err, syscall.EPIPE) { // Client has stopped listening.
			return
		}
		panic(fmt.Sprintf("Context.HTML - Error rendering template: %s. You may need to build frontend assets \n %s", name, err.Error()))
	}
}

func (ctx *Context) JSON(status int, data interface{}) {
	ctx.Resp.Header().Set(headerContentType, contentTypeJSON)
	ctx.Resp.WriteHeader(status)
	enc := json.NewEncoder(ctx.Resp)
	if Env != PROD {
		enc.SetIndent("", "  ")
	}
	if err := enc.Encode(data); err != nil {
		panic("Context.JSON: " + err.Error())
	}
}

// Redirect sends a redirect response
func (ctx *Context) Redirect(location string, status ...int) {
	code := http.StatusFound
	if len(status) == 1 {
		code = status[0]
	}

	http.Redirect(ctx.Resp, ctx.Req, location, code)
}

// MaxMemory is the maximum amount of memory to use when parsing a multipart form.
// Set this to whatever value you prefer; default is 10 MB.
var MaxMemory = int64(1024 * 1024 * 10)

func (ctx *Context) parseForm() {
	if ctx.Req.Form != nil {
		return
	}

	contentType := ctx.Req.Header.Get(headerContentType)
	if (ctx.Req.Method == "POST" || ctx.Req.Method == "PUT") &&
		len(contentType) > 0 && strings.Contains(contentType, "multipart/form-data") {
		_ = ctx.Req.ParseMultipartForm(MaxMemory)
	} else {
		_ = ctx.Req.ParseForm()
	}
}

// Query querys form parameter.
func (ctx *Context) Query(name string) string {
	ctx.parseForm()
	return ctx.Req.Form.Get(name)
}

// QueryStrings returns a list of results by given query name.
func (ctx *Context) QueryStrings(name string) []string {
	ctx.parseForm()

	vals, ok := ctx.Req.Form[name]
	if !ok {
		return []string{}
	}
	return vals
}

// QueryBool returns query result in bool type.
func (ctx *Context) QueryBool(name string) bool {
	v, _ := strconv.ParseBool(ctx.Query(name))
	return v
}

// QueryInt returns query result in int type.
func (ctx *Context) QueryInt(name string) int {
	n, _ := strconv.Atoi(ctx.Query(name))
	return n
}

// QueryInt64 returns query result in int64 type.
func (ctx *Context) QueryInt64(name string) int64 {
	n, _ := strconv.ParseInt(ctx.Query(name), 10, 64)
	return n
}

// GetCookie returns given cookie value from request header.
func (ctx *Context) GetCookie(name string) string {
	cookie, err := ctx.Req.Cookie(name)
	if err != nil {
		return ""
	}
	val, _ := url.QueryUnescape(cookie.Value)
	return val
}