package main

import (
	"bufio"
	"flag"
	"log"
	"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
	Verbose    bool
}

func RewritesFromConfig(cfgfile string) (*trie.Trie, error) {
	t := trie.NewTrie()
	cfg, err := config.Load(cfgfile)
	if err != nil {
		return &t, 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
			}
			log.Printf("Fetching %s mirrors %v", distroName, repoList)
			wg.Add(1)
			go d.FetchMirrors(repoList, repoMirrors, &wg)
		}

		wg.Wait()
		close(repoMirrors)
		if len(repoMirrors) > 0 {
			log.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 {
				log.Printf("Loading static rewites for %s", r.Name)
			}
			for _, url := range r.Urls {
				t.Put(url, r.Destination)
			}
		}
		if r.Filename != "" {
			if Flags.Verbose {
				log.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 {
				log.Printf("Can't open file %s", r.Filename)
			}
		}
	}

	return &t, nil
}

func Rewrite(t *trie.Trie) {
	log.Println("Listening for requests")
	scanner := bufio.NewScanner(os.Stdin)
	for scanner.Scan() {
		req := squid.ParseRequest(scanner.Text())
		if req == nil {
			continue
		}
		resp := req.MakeResponse()
		if req.Url != "" {
			resp.Result = "OK"
			prefix, dest := t.GetLongestPrefix(req.Url)
			if sdest, ok := dest.(string); ok {
				newUrl := sdest + req.Url[len(prefix):]
				resp.RewriteTo(newUrl)
				if Flags.Verbose {
					log.Printf("Rewriting %s to %s", req.Url, newUrl)
				}
			}
		} else {
			resp.Result = "ERR"
		}
		os.Stdout.WriteString(resp.Format() + "\n")
	}
	log.Println("End of input stream. Exiting.")
}

func init() {
	flag.StringVar(&Flags.ConfigFile, "c", "", "Path to rewrite config file")
	flag.BoolVar(&Flags.Verbose, "v", false, "Verbose logging")
}

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

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

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

	return t
}

func main() {
	flag.Parse()
	Rewrite(LoadRewrites())
}