package main

import (
	"bufio"
	"flag"
	"io"
	"log"
	"net"
	"os"
	"strings"
	"sync"
	"time"

	"git.worn.eu/guru/squid-rewriter/config"
	"git.worn.eu/guru/squid-rewriter/distro"
	"git.worn.eu/guru/squid-rewriter/squid"
	"git.worn.eu/guru/squid-rewriter/trie"
)

var Flags struct {
	ConfigFile    string
	LogFile       string
	DumpFile      string
	Verbose       bool
	ListenAddress string
}

var ready = false
var L *log.Logger

func RewritesFromConfig(t *trie.Trie, cfgfile string) error {
	cfg, err := config.Load(cfgfile)
	if err != nil {
		return err
	}

	repoRewrites := make(map[string]map[string]string, 100)

	for _, r := range cfg.Rewrites {
		if r.Destination == "" {
			continue
		}
		if r.Distro != "" {
			distroName := r.Distro
			repoName := "main"
			if strings.Contains(distroName, ":") {
				f := strings.SplitN(distroName, ":", 2)
				distroName = f[0]
				repoName = f[1]
			}
			if _, ok := repoRewrites[distroName]; !ok {
				repoRewrites[distroName] = make(map[string]string)
			}
			repoRewrites[distroName][repoName] = r.Destination
		}
	}

	if len(repoRewrites) > 0 {
		repoMirrors := make(chan distro.RepoMirror)
		wg := sync.WaitGroup{}

		go func() {
			for r := range repoMirrors {
				d, ok := repoRewrites[r.Distro]
				if !ok {
					continue
				}
				destination, ok := d[r.Repo]
				if !ok {
					continue
				}
				t.Put(r.Url, destination)
			}
		}()

		for distroName, repos := range repoRewrites {
			repoList := []string{}
			for r := range repos {
				repoList = append(repoList, r)
			}
			d := distro.GetDistro(distroName)
			if d == nil {
				continue
			}
			L.Printf("Fetching %s mirrors %v", distroName, repoList)
			wg.Add(1)
			go d.FetchMirrors(repoList, repoMirrors, &wg)
		}

		wg.Wait()
		close(repoMirrors)
		if len(repoMirrors) > 0 {
			L.Println("Waiting for all repo rewrite rules to be processed...")
			for len(repoMirrors) > 0 {
				time.Sleep(5 * time.Millisecond)
			}
		}
	}

	for _, r := range cfg.Rewrites {
		if r.Destination == "" {
			continue
		}
		if len(r.Urls) > 0 {
			if Flags.Verbose {
				L.Printf("Loading static rewites for %s", r.Name)
			}
			for _, url := range r.Urls {
				t.Put(url, r.Destination)
			}
		}
		if r.Filename != "" {
			if Flags.Verbose {
				L.Printf("Loading rewrites from %s for %s", r.Filename, r.Name)
			}
			f, err := os.Open(r.Filename)
			if err == nil {
				defer f.Close()
				scanner := bufio.NewScanner(f)
				for scanner.Scan() {
					line := strings.TrimSpace(scanner.Text())
					if line != "" && !strings.HasPrefix(line, "#") {
						if line != r.Destination {
							t.Put(line, r.Destination)
						}
					}
				}
			} else {
				L.Printf("Can't open file %s", r.Filename)
			}
		}
	}

	ready = true

	return nil
}

func Rewrite(t *trie.Trie, r io.ReadCloser, w io.WriteCloser, closeStreams bool) {
	scanner := bufio.NewScanner(r)
	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		if Flags.Verbose {
			L.Println("Parsing request:", line)
		}
		req := squid.ParseRequest(line)
		if req == nil {
			continue
		}
		resp := req.MakeResponse()
		resp.Result = "ERR"
		if req.Url != "" && ready {
			prefix, dest := t.GetLongestPrefix(req.Url)
			if sdest, ok := dest.(string); ok {
				resp.Result = "OK"
				newUrl := sdest + req.Url[len(prefix):]
				resp.RewriteTo(newUrl)
				resp.StoreId(newUrl)
				if Flags.Verbose {
					L.Printf("Rewriting %s to %s", req.Url, newUrl)
				}
			}
		}
		w.Write([]byte(resp.Format() + "\n"))
	}
	if closeStreams {
		r.Close()
		w.Close()
	}
}

func init() {
	flag.StringVar(&Flags.ConfigFile, "c", "", "Path to rewrite config file")
	flag.StringVar(&Flags.LogFile, "log", "", "Path to log file")
	flag.StringVar(&Flags.DumpFile, "dump", "", "Path to dump file")
	flag.BoolVar(&Flags.Verbose, "v", false, "Verbose logging")
	flag.StringVar(&Flags.ListenAddress, "listen", "", "Listening address")
}

var RewriteFileNames []string = []string{"rewrites.yaml", "rewrites.yml", "/etc/squid/rewrites.yaml", "/etc/squid/rewrites.yml"}

func LoadRewrites(t *trie.Trie) {
	var err error

	start := time.Now()
	if Flags.ConfigFile != "" {
		err = RewritesFromConfig(t, Flags.ConfigFile)
		if err != nil {
			L.Fatalf("Can't load the specified rewrite file: %s", Flags.ConfigFile)
		}
	} else {
		for _, filename := range RewriteFileNames {
			if Flags.Verbose {
				L.Printf("Trying to load rewrites from %s", filename)
			}
			err = RewritesFromConfig(t, filename)
			if err == nil {
				break
			}
		}
		if err != nil {
			L.Fatalf("Can't load any of the predefined rewrite files: %v", RewriteFileNames)
		}
	}
	elapsed := time.Since(start)
	L.Printf("Loaded %d unique rewrites in %s", t.Count(), elapsed)

	if Flags.DumpFile != "" {
		file, err := os.OpenFile(Flags.DumpFile, os.O_TRUNC|os.O_CREATE|os.O_WRONLY, 0644)
		if err != nil {
			L.Fatal(err)
		}
		defer file.Close()

		t.Dump(file)
	}
}

func main() {
	flag.Parse()
	if Flags.LogFile != "" {
		file, err := os.OpenFile(Flags.LogFile, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
		if err != nil {
			L.Fatal(err)
		}
		defer file.Close()

		L = log.New(file, "", log.LstdFlags)
	} else {
		L = log.Default()
	}
	t := trie.NewTrie()
	go LoadRewrites(&t)
	if Flags.ListenAddress == "" {
		L.Println("Accepting requests from stdin")
		Rewrite(&t, os.Stdin, os.Stdout, false)
		L.Println("End of input stream. Exiting.")
	} else {
		listen, err := net.Listen("tcp", Flags.ListenAddress)
		if err != nil {
			L.Fatal(err)
		}
		defer listen.Close()
		for {
			conn, err := listen.Accept()
			if err != nil {
				log.Fatal(err)
			}
			go func() {
				client := conn.RemoteAddr().String()
				L.Printf("Accepting requests from client %s", client)
				Rewrite(&t, conn, conn, true)
				L.Printf("Client %s disconnected", client)
			}()
		}
	}
}