package repo

import (
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net/http"
	"net/url"
	"os"
	"path/filepath"
	"runtime"
	"sort"
	"strings"

	cp "github.com/Masterminds/glide/cache"
	"github.com/Masterminds/glide/cfg"
	"github.com/Masterminds/glide/msg"
	gpath "github.com/Masterminds/glide/path"
	"github.com/Masterminds/semver"
	v "github.com/Masterminds/vcs"
)

// VcsUpdate updates to a particular checkout based on the VCS setting.
func VcsUpdate(dep *cfg.Dependency, force bool, updated *UpdateTracker) error {

	// If the dependency has already been pinned we can skip it. This is a
	// faster path so we don't need to resolve it again.
	if dep.Pin != "" {
		msg.Debug("Dependency %s has already been pinned. Fetching updates skipped.", dep.Name)
		return nil
	}

	if updated.Check(dep.Name) {
		msg.Debug("%s was already updated, skipping.", dep.Name)
		return nil
	}
	updated.Add(dep.Name)

	if filterArchOs(dep) {
		msg.Info("%s is not used for %s/%s.\n", dep.Name, runtime.GOOS, runtime.GOARCH)
		return nil
	}

	key, err := cp.Key(dep.Remote())
	if err != nil {
		msg.Die("Cache key generation error: %s", err)
	}
	location := cp.Location()
	dest := filepath.Join(location, "src", key)

	// If destination doesn't exist we need to perform an initial checkout.
	if _, err := os.Stat(dest); os.IsNotExist(err) {
		msg.Info("--> Fetching %s.", dep.Name)
		if err = VcsGet(dep); err != nil {
			msg.Warn("Unable to checkout %s\n", dep.Name)
			return err
		}
	} else {
		// At this point we have a directory for the package.
		msg.Info("--> Fetching updates for %s.", dep.Name)

		// When the directory is not empty and has no VCS directory it's
		// a vendored files situation.
		empty, err := gpath.IsDirectoryEmpty(dest)
		if err != nil {
			return err
		}
		_, err = v.DetectVcsFromFS(dest)
		if empty == true && err == v.ErrCannotDetectVCS {
			msg.Warn("Cached version of %s is an empty directory. Fetching a new copy of the dependency.", dep.Name)
			msg.Debug("Removing empty directory %s", dest)
			err := os.RemoveAll(dest)
			if err != nil {
				return err
			}
			if err = VcsGet(dep); err != nil {
				msg.Warn("Unable to checkout %s\n", dep.Name)
				return err
			}
		} else {
			repo, err := dep.GetRepo(dest)

			// Tried to checkout a repo to a path that does not work. Either the
			// type or endpoint has changed. Force is being passed in so the old
			// location can be removed and replaced with the new one.
			// Warning, any changes in the old location will be deleted.
			// TODO: Put dirty checking in on the existing local checkout.
			if (err == v.ErrWrongVCS || err == v.ErrWrongRemote) && force == true {
				newRemote := dep.Remote()

				msg.Warn("Replacing %s with contents from %s\n", dep.Name, newRemote)
				rerr := os.RemoveAll(dest)
				if rerr != nil {
					return rerr
				}
				if err = VcsGet(dep); err != nil {
					msg.Warn("Unable to checkout %s\n", dep.Name)
					return err
				}

				repo, err = dep.GetRepo(dest)
				if err != nil {
					return err
				}
			} else if err != nil {
				return err
			} else if repo.IsDirty() {
				return fmt.Errorf("%s contains uncommitted changes. Skipping update", dep.Name)
			}

			ver := dep.Reference
			if ver == "" {
				ver = defaultBranch(repo)
			}
			// Check if the current version is a tag or commit id. If it is
			// and that version is already checked out we can skip updating
			// which is faster than going out to the Internet to perform
			// an update.
			if ver != "" {
				version, err := repo.Version()
				if err != nil {
					return err
				}
				ib, err := isBranch(ver, repo)
				if err != nil {
					return err
				}

				// If the current version equals the ref and it's not a
				// branch it's a tag or commit id so we can skip
				// performing an update.
				if version == ver && !ib {
					msg.Debug("%s is already set to version %s. Skipping update.", dep.Name, dep.Reference)
					return nil
				}
			}

			if err := repo.Update(); err != nil {
				msg.Warn("Download failed.\n")
				return err
			}
		}
	}

	return nil
}

// VcsVersion set the VCS version for a checkout.
func VcsVersion(dep *cfg.Dependency) error {

	// If the dependency has already been pinned we can skip it. This is a
	// faster path so we don't need to resolve it again.
	if dep.Pin != "" {
		msg.Debug("Dependency %s has already been pinned. Setting version skipped.", dep.Name)
		return nil
	}

	key, err := cp.Key(dep.Remote())
	if err != nil {
		msg.Die("Cache key generation error: %s", err)
	}
	location := cp.Location()
	cwd := filepath.Join(location, "src", key)

	// If there is no reference configured there is nothing to set.
	if dep.Reference == "" {
		// Before exiting update the pinned version
		repo, err := dep.GetRepo(cwd)
		if err != nil {
			return err
		}
		dep.Pin, err = repo.Version()
		if err != nil {
			return err
		}
		return nil
	}

	// When the directory is not empty and has no VCS directory it's
	// a vendored files situation.
	empty, err := gpath.IsDirectoryEmpty(cwd)
	if err != nil {
		return err
	}
	_, err = v.DetectVcsFromFS(cwd)
	if empty == false && err == v.ErrCannotDetectVCS {
		return fmt.Errorf("Cache directory missing VCS information for %s", dep.Name)
	}

	repo, err := dep.GetRepo(cwd)
	if err != nil {
		return err
	}

	ver := dep.Reference
	// References in Git can begin with a ^ which is similar to semver.
	// If there is a ^ prefix we assume it's a semver constraint rather than
	// part of the git/VCS commit id.
	if repo.IsReference(ver) && !strings.HasPrefix(ver, "^") {
		msg.Info("--> Setting version for %s to %s.\n", dep.Name, ver)
	} else {

		// Create the constraint first to make sure it's valid before
		// working on the repo.
		constraint, err := semver.NewConstraint(ver)

		// Make sure the constriant is valid. At this point it's not a valid
		// reference so if it's not a valid constrint we can exit early.
		if err != nil {
			msg.Warn("The reference '%s' is not valid\n", ver)
			return err
		}

		// Get the tags and branches (in that order)
		refs, err := getAllVcsRefs(repo)
		if err != nil {
			return err
		}

		// Convert and filter the list to semver.Version instances
		semvers := getSemVers(refs)

		// Sort semver list
		sort.Sort(sort.Reverse(semver.Collection(semvers)))
		found := false
		for _, v := range semvers {
			if constraint.Check(v) {
				found = true
				// If the constrint passes get the original reference
				ver = v.Original()
				break
			}
		}
		if found {
			msg.Info("--> Detected semantic version. Setting version for %s to %s.", dep.Name, ver)
		} else {
			msg.Warn("--> Unable to find semantic version for constraint %s %s", dep.Name, ver)
		}
	}
	if err := repo.UpdateVersion(ver); err != nil {
		return err
	}
	dep.Pin, err = repo.Version()
	if err != nil {
		return err
	}

	return nil
}

// VcsGet figures out how to fetch a dependency, and then gets it.
//
// VcsGet installs into the cache.
func VcsGet(dep *cfg.Dependency) error {

	key, err := cp.Key(dep.Remote())
	if err != nil {
		msg.Die("Cache key generation error: %s", err)
	}
	location := cp.Location()
	d := filepath.Join(location, "src", key)

	repo, err := dep.GetRepo(d)
	if err != nil {
		return err
	}
	// If the directory does not exist this is a first cache.
	if _, err = os.Stat(d); os.IsNotExist(err) {
		msg.Debug("Adding %s to the cache for the first time", dep.Name)
		err = repo.Get()
		if err != nil {
			return err
		}
		branch := findCurrentBranch(repo)
		if branch != "" {
			msg.Debug("Saving default branch for %s", repo.Remote())
			c := cp.RepoInfo{DefaultBranch: branch}
			err = cp.SaveRepoData(key, c)
			if err == cp.ErrCacheDisabled {
				msg.Debug("Unable to cache default branch because caching is disabled")
			} else if err != nil {
				msg.Debug("Error saving %s to cache. Error: %s", repo.Remote(), err)
			}
		}
	} else {
		msg.Debug("Updating %s in the cache", dep.Name)
		err = repo.Update()
		if err != nil {
			return err
		}
	}

	return nil
}

// filterArchOs indicates a dependency should be filtered out because it is
// the wrong GOOS or GOARCH.
//
// FIXME: Should this be moved to the dependency package?
func filterArchOs(dep *cfg.Dependency) bool {
	found := false
	if len(dep.Arch) > 0 {
		for _, a := range dep.Arch {
			if a == runtime.GOARCH {
				found = true
			}
		}
		// If it's not found, it should be filtered out.
		if !found {
			return true
		}
	}

	found = false
	if len(dep.Os) > 0 {
		for _, o := range dep.Os {
			if o == runtime.GOOS {
				found = true
			}
		}
		if !found {
			return true
		}

	}

	return false
}

// isBranch returns true if the given string is a branch in VCS.
func isBranch(branch string, repo v.Repo) (bool, error) {
	branches, err := repo.Branches()
	if err != nil {
		return false, err
	}
	for _, b := range branches {
		if b == branch {
			return true, nil
		}
	}
	return false, nil
}

// defaultBranch tries to ascertain the default branch for the given repo.
// Some repos will have multiple branches in them (e.g. Git) while others
// (e.g. Svn) will not.
func defaultBranch(repo v.Repo) string {

	// Svn and Bzr use different locations (paths or entire locations)
	// for branches so we won't have a default branch.
	if repo.Vcs() == v.Svn || repo.Vcs() == v.Bzr {
		return ""
	}

	// Check the cache for a value.
	key, kerr := cp.Key(repo.Remote())
	var d cp.RepoInfo
	if kerr == nil {
		d, err := cp.RepoData(key)
		if err == nil {
			if d.DefaultBranch != "" {
				return d.DefaultBranch
			}
		}
	}

	// If we don't have it in the store try some APIs
	r := repo.Remote()
	u, err := url.Parse(r)
	if err != nil {
		return ""
	}
	if u.Scheme == "" {
		// Where there is no scheme we try urls like git@github.com:foo/bar
		r = strings.Replace(r, ":", "/", -1)
		r = "ssh://" + r
		u, err = url.Parse(r)
		if err != nil {
			return ""
		}
		u.Scheme = ""
	}
	if u.Host == "github.com" {
		parts := strings.Split(u.Path, "/")
		if len(parts) != 2 {
			return ""
		}
		api := fmt.Sprintf("https://api.github.com/repos/%s/%s", parts[0], parts[1])
		resp, err := http.Get(api)
		if err != nil {
			return ""
		}
		defer resp.Body.Close()
		if resp.StatusCode >= 300 || resp.StatusCode < 200 {
			return ""
		}
		body, err := ioutil.ReadAll(resp.Body)
		var data interface{}
		err = json.Unmarshal(body, &data)
		if err != nil {
			return ""
		}
		gh := data.(map[string]interface{})
		db := gh["default_branch"].(string)
		if kerr == nil {
			d.DefaultBranch = db
			err := cp.SaveRepoData(key, d)
			if err == cp.ErrCacheDisabled {
				msg.Debug("Unable to cache default branch because caching is disabled")
			} else if err != nil {
				msg.Debug("Error saving %s to cache. Error: %s", repo.Remote(), err)
			}
		}
		return db
	}

	if u.Host == "bitbucket.org" {
		parts := strings.Split(u.Path, "/")
		if len(parts) != 2 {
			return ""
		}
		api := fmt.Sprintf("https://bitbucket.org/api/1.0/repositories/%s/%s/main-branch/", parts[0], parts[1])
		resp, err := http.Get(api)
		if err != nil {
			return ""
		}
		defer resp.Body.Close()
		if resp.StatusCode >= 300 || resp.StatusCode < 200 {
			return ""
		}
		body, err := ioutil.ReadAll(resp.Body)
		var data interface{}
		err = json.Unmarshal(body, &data)
		if err != nil {
			return ""
		}
		bb := data.(map[string]interface{})
		db := bb["name"].(string)
		if kerr == nil {
			d.DefaultBranch = db
			err := cp.SaveRepoData(key, d)
			if err == cp.ErrCacheDisabled {
				msg.Debug("Unable to cache default branch because caching is disabled")
			} else if err != nil {
				msg.Debug("Error saving %s to cache. Error: %s", repo.Remote(), err)
			}
		}
		return db
	}

	return ""
}

// From a local repo find out the current branch name if there is one.
// Note, this should only be used right after a fresh clone to get accurate
// information.
func findCurrentBranch(repo v.Repo) string {
	msg.Debug("Attempting to find current branch for %s", repo.Remote())
	// Svn and Bzr don't have default branches.
	if repo.Vcs() == v.Svn || repo.Vcs() == v.Bzr {
		return ""
	}

	if repo.Vcs() == v.Git || repo.Vcs() == v.Hg {
		ver, err := repo.Current()
		if err != nil {
			msg.Debug("Unable to find current branch for %s, error: %s", repo.Remote(), err)
			return ""
		}
		return ver
	}

	return ""
}

func envForDir(dir string) []string {
	env := os.Environ()
	return mergeEnvLists([]string{"PWD=" + dir}, env)
}

func mergeEnvLists(in, out []string) []string {
NextVar:
	for _, inkv := range in {
		k := strings.SplitAfterN(inkv, "=", 2)[0]
		for i, outkv := range out {
			if strings.HasPrefix(outkv, k) {
				out[i] = inkv
				continue NextVar
			}
		}
		out = append(out, inkv)
	}
	return out
}