// Package cache provides an interface for interfacing with the Glide local cache
package cache

import (
	"encoding/json"
	"errors"
	"io/ioutil"
	"net/url"
	"os"
	"path/filepath"
	"regexp"
	"strings"
	"sync"
	"time"

	"github.com/Masterminds/glide/msg"
	gpath "github.com/Masterminds/glide/path"
)

// Enabled sets if the cache is globally enabled. Defaults to true.
var Enabled = true

// ErrCacheDisabled is returned with the cache is disabled.
var ErrCacheDisabled = errors.New("Cache disabled")

var isSetup bool

var setupMutex sync.Mutex

func setup() error {
	setupMutex.Lock()
	defer setupMutex.Unlock()

	if isSetup {
		return nil
	}
	msg.Debug("Setting up the cache directory")
	pths := []string{
		"cache",
		filepath.Join("cache", "src"),
		filepath.Join("cache", "info"),
	}

	for _, l := range pths {
		err := os.MkdirAll(filepath.Join(gpath.Home(), l), 0755)
		if err != nil {
			return err
		}
	}

	isSetup = true
	return nil
}

// Location returns the location of the cache.
func Location() (string, error) {
	p := filepath.Join(gpath.Home(), "cache")
	err := setup()

	return p, err
}

// scpSyntaxRe matches the SCP-like addresses used to access repos over SSH.
var scpSyntaxRe = regexp.MustCompile(`^([a-zA-Z0-9_]+)@([a-zA-Z0-9._-]+):(.*)$`)

// Key generates a cache key based on a url or scp string. The key is file
// system safe.
func Key(repo string) (string, error) {

	var u *url.URL
	var err error
	var strip bool
	if m := scpSyntaxRe.FindStringSubmatch(repo); m != nil {
		// Match SCP-like syntax and convert it to a URL.
		// Eg, "git@github.com:user/repo" becomes
		// "ssh://git@github.com/user/repo".
		u = &url.URL{
			Scheme: "ssh",
			User:   url.User(m[1]),
			Host:   m[2],
			Path:   "/" + m[3],
		}
		strip = true
	} else {
		u, err = url.Parse(repo)
		if err != nil {
			return "", err
		}
	}

	if strip {
		u.Scheme = ""
	}

	var key string
	if u.Scheme != "" {
		key = u.Scheme + "-"
	}
	if u.User != nil && u.User.Username() != "" {
		key = key + u.User.Username() + "-"
	}
	key = key + u.Host
	if u.Path != "" {
		key = key + strings.Replace(u.Path, "/", "-", -1)
	}

	key = strings.Replace(key, ":", "-", -1)

	return key, nil
}

// RepoInfo holds information about a repo.
type RepoInfo struct {
	DefaultBranch string `json:"default-branch"`
	LastUpdate    string `json:"last-update"`
}

// SaveRepoData stores data about a repo in the Glide cache
func SaveRepoData(key string, data RepoInfo) error {
	if !Enabled {
		return ErrCacheDisabled
	}
	location, err := Location()
	if err != nil {
		return err
	}
	data.LastUpdate = time.Now().String()
	d, err := json.Marshal(data)
	if err != nil {
		return err
	}

	pp := filepath.Join(location, "info")
	err = os.MkdirAll(pp, 0755)
	if err != nil {
		return err
	}

	p := filepath.Join(pp, key+".json")
	f, err := os.Create(p)
	if err != nil {
		return err
	}
	defer f.Close()

	_, err = f.Write(d)
	return err
}

// RepoData retrieves cached information about a repo.
func RepoData(key string) (*RepoInfo, error) {
	if !Enabled {
		return &RepoInfo{}, ErrCacheDisabled
	}
	location, err := Location()
	if err != nil {
		return &RepoInfo{}, err
	}
	c := &RepoInfo{}
	p := filepath.Join(location, "info", key+".json")
	f, err := ioutil.ReadFile(p)
	if err != nil {
		return &RepoInfo{}, err
	}
	err = json.Unmarshal(f, c)
	if err != nil {
		return &RepoInfo{}, err
	}
	return c, nil
}