package locking

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

	"github.com/git-lfs/git-lfs/errors"
	"github.com/git-lfs/git-lfs/git"
	"github.com/git-lfs/git-lfs/lfsapi"
	"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")
)

type LockCacher interface {
	Add(l Lock) error
	RemoveByPath(filePath string) error
	RemoveById(id string) error
	Locks() []Lock
	Clear()
	Save() error
}

// Client is the main interface object for the locking package
type Client struct {
	Remote string
	client *lockClient
	cache  LockCacher
}

// 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(remote string, lfsClient *lfsapi.Client) (*Client, error) {
	return &Client{
		Remote: remote,
		client: &lockClient{Client: lfsClient},
		cache:  &nilLockCacher{},
	}, nil
}

func (c *Client) SetupFileCache(path string) error {
	stat, err := os.Stat(path)
	if err != nil {
		return errors.Wrap(err, "init lock cache")
	}

	lockFile := path
	if stat.IsDir() {
		lockFile = filepath.Join(path, "lockcache.db")
	}

	cache, err := NewLockCache(lockFile)
	if err != nil {
		return errors.Wrap(err, "init lock cache")
	}

	c.cache = cache
	return 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
	}

	lockReq := &lockRequest{
		Path:               path,
		LatestRemoteCommit: latest.Sha,
		Committer:          newCommitter(c.client.CurrentUser()),
	}

	lockRes, _, err := c.client.Lock(c.Remote, lockReq)
	if err != nil {
		return Lock{}, errors.Wrap(err, "api")
	}

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

	lock := *lockRes.Lock
	if err := c.cache.Add(lock); err != nil {
		return Lock{}, errors.Wrap(err, "lock cache")
	}

	return lock, nil
}

// 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)
	}

	return c.UnlockFileById(id, force)

}

// 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 {
	unlockRes, _, err := c.client.Unlock(c.Remote, id, force)
	if err != nil {
		return errors.Wrap(err, "api")
	}

	if len(unlockRes.Err) > 0 {
		return fmt.Errorf("Server unable to unlock: %s", unlockRes.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 `json:"id"`
	// Path is an absolute path to the file that is locked as a part of this
	// lock.
	Path string `json:"path"`
	// Name is the name of the person holding this lock
	Name string `json:"name"`
	// Email address of the person holding this lock
	Email string `json:"email"`
	// LockedAt is the time at which this lock was acquired.
	LockedAt time.Time `json:"locked_at"`
}

// 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([]lockFilter, 0, len(filter))
	for k, v := range filter {
		apifilters = append(apifilters, lockFilter{Property: k, Value: v})
	}
	query := &lockSearchRequest{Filters: apifilters}
	for {
		list, _, err := c.client.Search(c.Remote, query)
		if err != nil {
			return locks, errors.Wrap(err, "locking")
		}

		if list.Err != "" {
			return locks, errors.Wrap(err, "locking")
		}

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

		if list.NextCursor != "" {
			query.Cursor = list.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) {
	list, _, err := c.client.Search(c.Remote, &lockSearchRequest{
		Filters: []lockFilter{
			{Property: "path", Value: path},
		},
	})

	if err != nil {
		return "", err
	}

	switch len(list.Locks) {
	case 0:
		return "", ErrNoMatchingLocks
	case 1:
		return list.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.client.CurrentUser()
	for _, l := range locks {
		if l.Email == email {
			c.cache.Add(l)
		}
	}

	return nil
}

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

type nilLockCacher struct{}

func (c *nilLockCacher) Add(l Lock) error {
	return nil
}
func (c *nilLockCacher) RemoveByPath(filePath string) error {
	return nil
}
func (c *nilLockCacher) RemoveById(id string) error {
	return nil
}
func (c *nilLockCacher) Locks() []Lock {
	return nil
}
func (c *nilLockCacher) Clear() {}
func (c *nilLockCacher) Save() error {
	return nil
}