// Copyright 2016 Google Inc. All rights reserved.
//
// 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 main

import (
	"bytes"
	"encoding/json"
	"io/ioutil"
	"log"
	"math/rand"
	"net/http"
	"net/url"
	"os"
	"os/exec"
	"path/filepath"
	"time"

	"github.com/fsnotify/fsnotify"
)

type ConfigEntry struct {
	GithubUser             string
	GithubOrg              string
	BitBucketServerProject string
	GitHubURL              string
	GitilesURL             string
	CGitURL                string
	BitBucketServerURL     string
	ProjectType            string
	Name                   string
	Exclude                string
	GitLabURL              string
}

func randomize(entries []ConfigEntry) []ConfigEntry {
	perm := rand.Perm(len(entries))

	var shuffled []ConfigEntry
	for _, i := range perm {
		shuffled = append(shuffled, entries[i])
	}

	return shuffled
}

func isHTTP(u string) bool {
	asURL, err := url.Parse(u)
	return err == nil && (asURL.Scheme == "http" || asURL.Scheme == "https")
}

func readConfigURL(u string) ([]ConfigEntry, error) {
	var body []byte
	var readErr error

	if isHTTP(u) {
		rep, err := http.Get(u)
		if err != nil {
			return nil, err
		}
		defer rep.Body.Close()

		body, readErr = ioutil.ReadAll(rep.Body)
	} else {
		body, readErr = ioutil.ReadFile(u)
	}

	if readErr != nil {
		return nil, readErr
	}

	var result []ConfigEntry
	if err := json.Unmarshal(body, &result); err != nil {
		return nil, err
	}
	return result, nil
}

func watchFile(path string) (<-chan struct{}, error) {
	watcher, err := fsnotify.NewWatcher()
	if err != nil {
		return nil, err
	}

	if err := watcher.Add(filepath.Dir(path)); err != nil {
		return nil, err
	}

	out := make(chan struct{}, 1)
	go func() {
		var last time.Time
		for {
			select {
			case <-watcher.Events:
				fi, err := os.Stat(path)
				if err == nil && fi.ModTime() != last {
					out <- struct{}{}
					last = fi.ModTime()
				}
			case err := <-watcher.Errors:
				if err != nil {
					log.Printf("watcher error: %v", err)
				}
			}
		}
	}()
	return out, nil
}

func periodicMirrorFile(repoDir string, opts *Options, pendingRepos chan<- string) {
	ticker := time.NewTicker(opts.mirrorInterval)

	var watcher <-chan struct{}
	if !isHTTP(opts.mirrorConfigFile) {
		var err error
		watcher, err = watchFile(opts.mirrorConfigFile)
		if err != nil {
			log.Printf("watchFile(%q): %v", opts.mirrorConfigFile, err)
		}
	}

	var lastCfg []ConfigEntry
	for {
		cfg, err := readConfigURL(opts.mirrorConfigFile)
		if err != nil {
			log.Printf("readConfig(%s): %v", opts.mirrorConfigFile, err)
		} else {
			lastCfg = cfg
		}

		executeMirror(lastCfg, repoDir, pendingRepos)

		select {
		case <-watcher:
			log.Printf("mirror config %s changed", opts.mirrorConfigFile)
		case <-ticker.C:
		}
	}
}

func executeMirror(cfg []ConfigEntry, repoDir string, pendingRepos chan<- string) {
	// Randomize the ordering in which we query
	// things. This is to ensure that quota limits don't
	// always hit the last one in the list.
	cfg = randomize(cfg)
	for _, c := range cfg {
		var cmd *exec.Cmd
		if c.GithubUser != "" || c.GithubOrg != "" {
			cmd = exec.Command("zoekt-mirror-github",
				"-dest", repoDir)
			if c.GitHubURL != "" {
				cmd.Args = append(cmd.Args, "-url", c.GitHubURL)
			}
			if c.GithubUser != "" {
				cmd.Args = append(cmd.Args, "-user", c.GithubUser)
			} else if c.GithubOrg != "" {
				cmd.Args = append(cmd.Args, "-org", c.GithubOrg)
			}
			if c.Name != "" {
				cmd.Args = append(cmd.Args, "-name", c.Name)
			}
			if c.Exclude != "" {
				cmd.Args = append(cmd.Args, "-exclude", c.Exclude)
			}
		} else if c.GitilesURL != "" {
			cmd = exec.Command("zoekt-mirror-gitiles",
				"-dest", repoDir, "-name", c.Name)
			if c.Exclude != "" {
				cmd.Args = append(cmd.Args, "-exclude", c.Exclude)
			}
			cmd.Args = append(cmd.Args, c.GitilesURL)
		} else if c.CGitURL != "" {
			cmd = exec.Command("zoekt-mirror-gitiles",
				"-type", "cgit",
				"-dest", repoDir, "-name", c.Name)
			if c.Exclude != "" {
				cmd.Args = append(cmd.Args, "-exclude", c.Exclude)
			}
			cmd.Args = append(cmd.Args, c.CGitURL)
		} else if c.BitBucketServerURL != "" {
			cmd = exec.Command("zoekt-mirror-bitbucket-server",
				"-dest", repoDir, "-url", c.BitBucketServerURL)
			if c.BitBucketServerProject != "" {
				cmd.Args = append(cmd.Args, "-project", c.BitBucketServerProject)
			}
			if c.ProjectType != "" {
				cmd.Args = append(cmd.Args, "-type", c.ProjectType)
			}
			if c.Name != "" {
				cmd.Args = append(cmd.Args, "-name", c.Name)
			}
			if c.Exclude != "" {
				cmd.Args = append(cmd.Args, "-exclude", c.Exclude)
			}
		} else if c.GitLabURL != "" {
			cmd = exec.Command("zoekt-mirror-gitlab",
				"-dest", repoDir, "-url", c.GitLabURL)
			if c.Name != "" {
				cmd.Args = append(cmd.Args, "-name", c.Name)
			}
			if c.Exclude != "" {
				cmd.Args = append(cmd.Args, "-exclude", c.Exclude)
			}
		}

		stdout, _ := loggedRun(cmd)

		for _, fn := range bytes.Split(stdout, []byte{'\n'}) {
			if len(fn) == 0 {
				continue
			}

			pendingRepos <- string(fn)
		}

	}
}