// Package fastcgi has middleware that acts as a FastCGI client. Requests
// that get forwarded to FastCGI stop the middleware execution chain.
// The most common use for this layer is to serve PHP websites via php-fpm.
package fastcgi

import (
	"io"
	"io/ioutil"
	"net/http"
	"path/filepath"
	"strings"

	"github.com/mholt/caddy/middleware"
)

// New generates a new FastCGI middleware.
func New(c middleware.Controller) (middleware.Middleware, error) {
	root := c.Root()

	var rules []fastCgi
	for c.Next() {
		rule := fastCgi{}
		if !c.Args(&rule.path, &rule.address) {
			return nil, c.ArgErr()
		}
		rules = append(rules, rule)
	}

	return func(next middleware.HandlerFunc) middleware.HandlerFunc {
		return func(w http.ResponseWriter, r *http.Request) (int, error) {

			servedFcgi := false
			for _, rule := range rules {
				if middleware.Path(r.URL.Path).Matches(rule.path) {
					servedFcgi = true

					// Get absolute file paths
					absPath, err := filepath.Abs(root + r.URL.Path)
					if err != nil {
						return http.StatusInternalServerError, err
					}

					// Get absolute file path to website root
					absRootPath, err := filepath.Abs(root)
					if err != nil {
						return http.StatusInternalServerError, err
					}

					// Separate remote IP and port
					var ip, port string
					if idx := strings.Index(r.RemoteAddr, ":"); idx > -1 {
						ip = r.RemoteAddr[idx:]
						port = r.RemoteAddr[:idx]
					} else {
						ip = r.RemoteAddr
					}

					// TODO: Do we really have to make this map from scratch for each request?
					// TODO: We have quite a few more to map, too.
					env := make(map[string]string)
					env["SERVER_SOFTWARE"] = "caddy" // TODO: Obtain version info...
					env["SERVER_PROTOCOL"] = r.Proto
					env["SCRIPT_FILENAME"] = absPath
					env["REMOTE_ADDR"] = ip
					env["REMOTE_PORT"] = port
					env["REQUEST_METHOD"] = r.Method
					env["QUERY_STRING"] = r.URL.RawQuery
					env["DOCUMENT_URI"] = r.URL.Path
					env["DOCUMENT_ROOT"] = absRootPath

					fcgi, err := Dial("tcp", rule.address)
					if err != nil {
						return http.StatusBadGateway, err
					}

					resp, err := fcgi.Get(env)
					if err != nil && err != io.EOF {
						return http.StatusBadGateway, err
					}

					body, err := ioutil.ReadAll(resp.Body)
					if err != nil {
						return http.StatusBadGateway, err
					}

					for key, vals := range resp.Header {
						for _, val := range vals {
							w.Header().Add(key, val)
						}
					}

					w.WriteHeader(resp.StatusCode)
					w.Write(body)

					break
				}
			}

			if !servedFcgi {
				return next(w, r)
			}

			return 0, nil
		}
	}, nil
}

type fastCgi struct {
	path    string
	address string
}