package locking

import (
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"sync"
	"time"

	"github.com/rubyist/tracerx"

	"github.com/git-lfs/git-lfs/api"
	"github.com/git-lfs/git-lfs/config"
	"github.com/git-lfs/git-lfs/filepathfilter"
	"github.com/git-lfs/git-lfs/git"
	"github.com/git-lfs/git-lfs/tools"
	"github.com/git-lfs/git-lfs/tools/kv"
)

var (
	// ErrNoMatchingLocks is an error returned when no matching locks were
	// able to be resolved
	ErrNoMatchingLocks = errors.New("lfs: no matching locks found")
	// ErrLockAmbiguous is an error returned when multiple matching locks
	// were found
	ErrLockAmbiguous = errors.New("lfs: multiple locks found; ambiguous")
)

// Client is the main interface object for the locking package
type Client struct {
	cfg              *config.Configuration
	apiClient        *api.Client
	cache            *LockCache
	lockablePatterns []string
	lockableFilter   *filepathfilter.Filter
	lockableMutex    sync.Mutex

	LocalWorkingDir          string
	LocalGitDir              string
	SetLockableFilesReadOnly bool
}

// NewClient creates a new locking client with the given configuration
// You must call the returned object's `Close` method when you are finished with
// it
func NewClient(cfg *config.Configuration) (*Client, error) {

	apiClient := api.NewClient(api.NewHttpLifecycle(cfg))

	lockDir := filepath.Join(config.LocalGitStorageDir, "lfs")
	err := os.MkdirAll(lockDir, 0755)
	if err != nil {
		return nil, err
	}
	lockFile := filepath.Join(lockDir, "lockcache.db")
	cache, err := NewLockCache(lockFile)
	if err != nil {
		return nil, err
	}

	return &Client{
		cfg:                      cfg,
		apiClient:                apiClient,
		cache:                    cache,
		LocalWorkingDir:          config.LocalWorkingDir,
		LocalGitDir:              config.LocalGitDir,
		SetLockableFilesReadOnly: cfg.SetLockableFilesReadOnly()}, nil
}

// Close this client instance; must be called to dispose of resources
func (c *Client) Close() error {
	return c.cache.Save()
}

// LockFile attempts to lock a file on the current remote
// path must be relative to the root of the repository
// Returns the lock id if successful, or an error
func (c *Client) LockFile(path string) (Lock, error) {

	// TODO: this is not really the constraint we need to avoid merges, improve as per proposal
	latest, err := git.CurrentRemoteRef()
	if err != nil {
		return Lock{}, err
	}

	s, resp := c.apiClient.Locks.Lock(&api.LockRequest{
		Path:               path,
		Committer:          api.NewCommitter(c.cfg.CurrentCommitter()),
		LatestRemoteCommit: latest.Sha,
	})

	if _, err := c.apiClient.Do(s); err != nil {
		return Lock{}, fmt.Errorf("Error communicating with LFS API: %v", err)
	}

	if len(resp.Err) > 0 {
		return Lock{}, fmt.Errorf("Server unable to create lock: %v", resp.Err)
	}

	lock := c.newLockFromApi(*resp.Lock)

	if err := c.cache.Add(lock); err != nil {
		return Lock{}, fmt.Errorf("Error caching lock information: %v", err)
	}

	// Ensure writeable on return
	return lock, tools.SetFileWriteFlag(path, true)
}

// UnlockFile attempts to unlock a file on the current remote
// path must be relative to the root of the repository
// Force causes the file to be unlocked from other users as well
func (c *Client) UnlockFile(path string, force bool) error {

	id, err := c.lockIdFromPath(path)
	if err != nil {
		return fmt.Errorf("Unable to get lock id: %v", err)
	}

	err = c.UnlockFileById(id, force)
	if err != nil {
		return err
	}

	// Make non-writeable if required
	if c.SetLockableFilesReadOnly && c.IsFileLockable(path) {
		return tools.SetFileWriteFlag(path, false)
	}
	return nil

}

// UnlockFileById attempts to unlock a lock with a given id on the current remote
// Force causes the file to be unlocked from other users as well
func (c *Client) UnlockFileById(id string, force bool) error {
	s, resp := c.apiClient.Locks.Unlock(id, force)

	if _, err := c.apiClient.Do(s); err != nil {
		return fmt.Errorf("Error communicating with LFS API: %v", err)
	}

	if len(resp.Err) > 0 {
		return fmt.Errorf("Server unable to unlock lock: %v", resp.Err)
	}

	if err := c.cache.RemoveById(id); err != nil {
		return fmt.Errorf("Error caching unlock information: %v", err)
	}

	return nil
}

// Lock is a record of a locked file
type Lock struct {
	// Id is the unique identifier corresponding to this particular Lock. It
	// must be consistent with the local copy, and the server's copy.
	Id string
	// Path is an absolute path to the file that is locked as a part of this
	// lock.
	Path string
	// Name is the name of the person holding this lock
	Name string
	// Email address of the person holding this lock
	Email string
	// LockedAt is the time at which this lock was acquired.
	LockedAt time.Time
}

func (c *Client) newLockFromApi(a api.Lock) Lock {
	return Lock{
		Id:       a.Id,
		Path:     a.Path,
		Name:     a.Committer.Name,
		Email:    a.Committer.Email,
		LockedAt: a.LockedAt,
	}
}

// SearchLocks returns a channel of locks which match the given name/value filter
// If limit > 0 then search stops at that number of locks
// If localOnly = true, don't query the server & report only own local locks
func (c *Client) SearchLocks(filter map[string]string, limit int, localOnly bool) (locks []Lock, err error) {

	if localOnly {
		return c.searchCachedLocks(filter, limit)
	} else {
		return c.searchRemoteLocks(filter, limit)
	}
}

func (c *Client) searchCachedLocks(filter map[string]string, limit int) ([]Lock, error) {
	cachedlocks := c.cache.Locks()
	path, filterByPath := filter["path"]
	id, filterById := filter["id"]
	lockCount := 0
	locks := make([]Lock, 0, len(cachedlocks))
	for _, l := range cachedlocks {
		// Manually filter by Path/Id
		if (filterByPath && path != l.Path) ||
			(filterById && id != l.Id) {
			continue
		}
		locks = append(locks, l)
		lockCount++
		if limit > 0 && lockCount >= limit {
			break
		}
	}
	return locks, nil
}

func (c *Client) searchRemoteLocks(filter map[string]string, limit int) ([]Lock, error) {
	locks := make([]Lock, 0, limit)

	apifilters := make([]api.Filter, 0, len(filter))
	for k, v := range filter {
		apifilters = append(apifilters, api.Filter{k, v})
	}
	query := &api.LockSearchRequest{Filters: apifilters}
	for {
		s, resp := c.apiClient.Locks.Search(query)
		if _, err := c.apiClient.Do(s); err != nil {
			return locks, fmt.Errorf("Error communicating with LFS API: %v", err)
		}

		if resp.Err != "" {
			return locks, fmt.Errorf("Error response from LFS API: %v", resp.Err)
		}

		for _, l := range resp.Locks {
			locks = append(locks, c.newLockFromApi(l))
			if limit > 0 && len(locks) >= limit {
				// Exit outer loop too
				return locks, nil
			}
		}

		if resp.NextCursor != "" {
			query.Cursor = resp.NextCursor
		} else {
			break
		}
	}

	return locks, nil

}

// lockIdFromPath makes a call to the LFS API and resolves the ID for the locked
// locked at the given path.
//
// If the API call failed, an error will be returned. If multiple locks matched
// the given path (should not happen during real-world usage), an error will be
// returnd. If no locks matched the given path, an error will be returned.
//
// If the API call is successful, and only one lock matches the given filepath,
// then its ID will be returned, along with a value of "nil" for the error.
func (c *Client) lockIdFromPath(path string) (string, error) {
	s, resp := c.apiClient.Locks.Search(&api.LockSearchRequest{
		Filters: []api.Filter{
			{"path", path},
		},
	})

	if _, err := c.apiClient.Do(s); err != nil {
		return "", err
	}

	switch len(resp.Locks) {
	case 0:
		return "", ErrNoMatchingLocks
	case 1:
		return resp.Locks[0].Id, nil
	default:
		return "", ErrLockAmbiguous
	}
}

// Fetch locked files for the current committer and cache them locally
// This can be used to sync up locked files when moving machines
func (c *Client) refreshLockCache() error {
	// TODO: filters don't seem to currently define how to search for a
	// committer's email. Is it "committer.email"? For now, just iterate
	locks, err := c.SearchLocks(nil, 0, false)
	if err != nil {
		return err
	}

	// We're going to overwrite the entire local cache
	c.cache.Clear()

	_, email := c.cfg.CurrentCommitter()
	for _, l := range locks {
		if l.Email == email {
			c.cache.Add(l)
		}
	}

	return nil
}

// IsFileLockedByCurrentCommitter returns whether a file is locked by the
// current committer, as cached locally
func (c *Client) IsFileLockedByCurrentCommitter(path string) bool {

	filter := map[string]string{"path": path}
	locks, err := c.searchCachedLocks(filter, 1)
	if err != nil {
		tracerx.Printf("Error searching cached locks: %s\nForcing remote search", err)
		locks, _ = c.searchRemoteLocks(filter, 1)
	}
	return len(locks) > 0
}

func init() {
	kv.RegisterTypeForStorage(&Lock{})
}