package core

import (
	"context"
	"errors"
	"fmt"
	"io/fs"
	"os"
	"path/filepath"
	"slices"
	"strconv"
	"strings"
	"time"

	"github.com/Masterminds/squirrel"
	"github.com/deluan/rest"
	"github.com/navidrome/navidrome/core/storage"
	"github.com/navidrome/navidrome/log"
	"github.com/navidrome/navidrome/model"
	"github.com/navidrome/navidrome/model/metadata"
	"github.com/navidrome/navidrome/model/request"
	"github.com/navidrome/navidrome/server/events"
	"github.com/navidrome/navidrome/utils/slice"
)

// Watcher interface for managing file system watchers
type Watcher interface {
	Watch(ctx context.Context, lib *model.Library) error
	StopWatching(ctx context.Context, libraryID int) error
}

// Library provides business logic for library management and user-library associations
type Library interface {
	GetUserLibraries(ctx context.Context, userID string) (model.Libraries, error)
	SetUserLibraries(ctx context.Context, userID string, libraryIDs []int) error
	ValidateLibraryAccess(ctx context.Context, userID string, libraryID int) error

	Repository() rest.Repository[model.Library]
}

type libraryService struct {
	ds     model.DataStore
	broker events.Broker
	repo   *libraryRepositoryWrapper
}

// NewLibrary creates a new Library service
func NewLibrary(ds model.DataStore, scanner model.Scanner, watcher Watcher, broker events.Broker, pluginManager PluginUnloader) Library {
	return &libraryService{
		ds:     ds,
		broker: broker,
		repo: &libraryRepositoryWrapper{
			LibraryRepository: ds.Library(),
			ds:                ds,
			scanner:           scanner,
			watcher:           watcher,
			broker:            broker,
			pluginManager:     pluginManager,
		},
	}
}

// User-library association operations

func (s *libraryService) GetUserLibraries(ctx context.Context, userID string) (model.Libraries, error) {
	// Verify user exists
	if _, err := s.ds.User().Get(ctx, userID); err != nil {
		return nil, err
	}

	return s.ds.User().GetUserLibraries(ctx, userID)
}

func (s *libraryService) SetUserLibraries(ctx context.Context, userID string, libraryIDs []int) error {
	// Verify user exists
	user, err := s.ds.User().Get(ctx, userID)
	if err != nil {
		return err
	}

	// Admin users get all libraries automatically - don't allow manual assignment
	if user.IsAdmin {
		return fmt.Errorf("%w: cannot manually assign libraries to admin users", model.ErrValidation)
	}

	// Regular users must have at least one library
	if len(libraryIDs) == 0 {
		return fmt.Errorf("%w: at least one library must be assigned to non-admin users", model.ErrValidation)
	}

	// Validate all library IDs exist
	if len(libraryIDs) > 0 {
		if err := s.validateLibraryIDs(ctx, libraryIDs); err != nil {
			return err
		}
	}

	// Set user libraries
	err = s.ds.User().SetUserLibraries(ctx, userID, libraryIDs)
	if err != nil {
		return fmt.Errorf("error setting user libraries: %w", err)
	}

	// Send refresh event to all clients
	event := &events.RefreshResource{}
	libIDs := slice.Map(libraryIDs, func(id int) string { return strconv.Itoa(id) })
	event = event.With("user", userID).With("library", libIDs...)
	s.broker.SendBroadcastMessage(ctx, event)
	return nil
}

func (s *libraryService) ValidateLibraryAccess(ctx context.Context, userID string, libraryID int) error {
	user, ok := request.UserFrom(ctx)
	if !ok {
		return fmt.Errorf("user not found in context")
	}

	// Admin users have access to all libraries
	if user.IsAdmin {
		return nil
	}

	// Check if user has explicit access to this library
	libraries, err := s.ds.User().GetUserLibraries(ctx, userID)
	if err != nil {
		log.Error(ctx, "Error checking library access", "userID", userID, "libraryID", libraryID, err)
		return fmt.Errorf("error checking library access: %w", err)
	}

	for _, lib := range libraries {
		if lib.ID == libraryID {
			return nil
		}
	}

	return fmt.Errorf("%w: user does not have access to library %d", model.ErrNotAuthorized, libraryID)
}

// REST repository wrapper

func (s *libraryService) Repository() rest.Repository[model.Library] {
	return s.repo
}

var _ rest.Persistable[model.Library] = (*libraryRepositoryWrapper)(nil)

type libraryRepositoryWrapper struct {
	model.LibraryRepository
	ds            model.DataStore
	scanner       model.Scanner
	watcher       Watcher
	broker        events.Broker
	pluginManager PluginUnloader
}

func (r *libraryRepositoryWrapper) Save(ctx context.Context, lib *model.Library) (string, error) {
	if err := r.validateLibrary(ctx, lib); err != nil {
		return "", err
	}

	err := r.LibraryRepository.Put(ctx, lib)
	if err != nil {
		return "", r.mapError(err)
	}

	// Start watcher and trigger scan after successful library creation
	if r.watcher != nil {
		if err := r.watcher.Watch(ctx, lib); err != nil {
			log.Warn(ctx, "Failed to start watcher for new library", "libraryID", lib.ID, "name", lib.Name, "path", lib.Path, err)
		}
	}

	if r.scanner != nil {
		go r.triggerScan(ctx, lib, "new")
	}

	// Send library refresh event to all clients
	if r.broker != nil {
		event := &events.RefreshResource{}
		r.broker.SendBroadcastMessage(ctx, event.With("library", strconv.Itoa(lib.ID)))
		log.Debug(ctx, "Library created - sent refresh event", "libraryID", lib.ID, "name", lib.Name)
	}

	return strconv.Itoa(lib.ID), nil
}

func (r *libraryRepositoryWrapper) Update(ctx context.Context, id string, entity model.Library, cols ...string) error {
	lib := &entity
	libID, err := strconv.Atoi(id)
	if err != nil {
		return fmt.Errorf("invalid library ID: %s", id)
	}

	lib.ID = libID
	if err := r.validateLibrary(ctx, lib); err != nil {
		return err
	}

	// Get the original library to check if path changed
	originalLib, err := r.Get(ctx, libID)
	if err != nil {
		return r.mapError(err)
	}

	pathChanged := originalLib.Path != lib.Path
	pidChanged := (updatesColumn(cols, "pidAlbum") && originalLib.PIDAlbum != lib.PIDAlbum) ||
		(updatesColumn(cols, "pidTrack") && originalLib.PIDTrack != lib.PIDTrack)

	err = r.LibraryRepository.Put(ctx, lib, cols...)
	if err != nil {
		return r.mapError(err)
	}

	if pathChanged && r.watcher != nil {
		if err := r.watcher.Watch(ctx, lib); err != nil {
			log.Warn(ctx, "Failed to restart watcher for updated library", "libraryID", lib.ID, "name", lib.Name, "path", lib.Path, err)
		}
	}

	if (pathChanged || pidChanged) && r.scanner != nil {
		go r.triggerScan(ctx, lib, "updated")
	}

	// Send library refresh event to all clients
	if r.broker != nil {
		event := &events.RefreshResource{}
		r.broker.SendBroadcastMessage(ctx, event.With("library", id))
		log.Debug(ctx, "Library updated - sent refresh event", "libraryID", libID, "name", lib.Name)
	}

	return nil
}

func (r *libraryRepositoryWrapper) Delete(ctx context.Context, ids ...string) error {
	for _, id := range ids {
		if err := r.deleteOne(ctx, id); err != nil {
			return err
		}
	}
	return nil
}

func (r *libraryRepositoryWrapper) deleteOne(ctx context.Context, id string) error {
	libID, err := strconv.Atoi(id)
	if err != nil {
		return &rest.ValidationError{Errors: map[string]string{
			"id": "invalid library ID format",
		}}
	}

	// Get library info before deletion for logging
	lib, err := r.Get(ctx, libID)
	if err != nil {
		return r.mapError(err)
	}

	// Run the deletion in a transaction so the cascade delete and the orphaned-artist
	// reconciliation it triggers (see libraryRepository.Delete) commit atomically.
	err = r.ds.WithTx(func(tx model.DataStore) error {
		return tx.Library().Delete(ctx, libID)
	}, "delete library")
	if err != nil {
		return r.mapError(err)
	}

	// Stop watcher and trigger scan after successful library deletion to clean up orphaned data
	if r.watcher != nil {
		if err := r.watcher.StopWatching(ctx, libID); err != nil {
			log.Warn(ctx, "Failed to stop watcher for deleted library", "libraryID", libID, "name", lib.Name, "path", lib.Path, err)
		}
	}

	if r.scanner != nil {
		go r.triggerScan(ctx, lib, "deleted")
	}

	// Send library refresh event to all clients
	if r.broker != nil {
		event := &events.RefreshResource{}
		r.broker.SendBroadcastMessage(ctx, event.With("library", id))
		log.Debug(ctx, "Library deleted - sent refresh event", "libraryID", libID, "name", lib.Name)
	}

	// After successful deletion, check if any plugins were auto-disabled
	// and need to be unloaded from memory
	r.pluginManager.UnloadDisabledPlugins(ctx)

	return nil
}

// Helper methods

func (r *libraryRepositoryWrapper) mapError(err error) error {
	if err == nil {
		return nil
	}

	errStr := err.Error()

	// Handle database constraint violations.
	// TODO: Being tied to react-admin translations is not ideal, but this will probably go away with the new UI/API
	if strings.Contains(errStr, "UNIQUE constraint failed") {
		if strings.Contains(errStr, "library.name") {
			return &rest.ValidationError{Errors: map[string]string{"name": "ra.validation.unique"}}
		}
		if strings.Contains(errStr, "library.path") {
			return &rest.ValidationError{Errors: map[string]string{"path": "ra.validation.unique"}}
		}
	}

	return err
}

func (r *libraryRepositoryWrapper) validateLibrary(ctx context.Context, library *model.Library) error {
	validationErrors := make(map[string]string)

	if library.Name == "" {
		validationErrors["name"] = "ra.validation.required"
	}

	if library.Path == "" {
		validationErrors["path"] = "ra.validation.required"
	} else {
		// Validate path format and accessibility
		if err := r.validateLibraryPath(ctx, library); err != nil {
			validationErrors["path"] = err.Error()
		}
	}

	library.PIDAlbum = strings.TrimSpace(library.PIDAlbum)
	library.PIDTrack = strings.TrimSpace(library.PIDTrack)
	if err := metadata.ValidatePIDSpec(library.PIDAlbum, true); err != nil {
		validationErrors["pidAlbum"] = err.Error()
	}
	if err := metadata.ValidatePIDSpec(library.PIDTrack, false); err != nil {
		validationErrors["pidTrack"] = err.Error()
	}

	if len(validationErrors) > 0 {
		return &rest.ValidationError{Errors: validationErrors}
	}

	return nil
}

// updatesColumn reports whether an update with these columns writes col. No columns means all of them.
func updatesColumn(cols []string, col string) bool {
	return len(cols) == 0 || slices.Contains(cols, col)
}

func (r *libraryRepositoryWrapper) validateLibraryPath(ctx context.Context, library *model.Library) error {
	// Validate path format
	if !filepath.IsAbs(library.Path) {
		return fmt.Errorf("library path must be absolute")
	}

	// Clean the path to normalize it
	cleanPath := filepath.Clean(library.Path)
	library.Path = cleanPath

	// Check if path exists and is accessible using storage abstraction
	fileStore, err := storage.For(library.Path)
	if err != nil {
		return fmt.Errorf("invalid storage scheme: %w", err)
	}

	fsys, err := fileStore.FS()
	if err != nil {
		log.Warn(ctx, "Error validating library.path", "path", library.Path, err)
		return fmt.Errorf("resources.library.validation.pathInvalid")
	}

	// Check if root directory exists
	info, err := fs.Stat(fsys, ".")
	if err != nil {
		// Parse the error message to check for "not a directory"
		log.Warn(ctx, "Error stating library.path", "path", library.Path, err)
		errStr := err.Error()
		if strings.Contains(errStr, "not a directory") ||
			strings.Contains(errStr, "The directory name is invalid.") {
			return fmt.Errorf("resources.library.validation.pathNotDirectory")
		} else if os.IsNotExist(err) {
			return fmt.Errorf("resources.library.validation.pathNotFound")
		} else if os.IsPermission(err) {
			return fmt.Errorf("resources.library.validation.pathNotAccessible")
		} else {
			return fmt.Errorf("resources.library.validation.pathInvalid")
		}
	}

	if !info.IsDir() {
		return fmt.Errorf("resources.library.validation.pathNotDirectory")
	}

	return nil
}

func (s *libraryService) validateLibraryIDs(ctx context.Context, libraryIDs []int) error {
	if len(libraryIDs) == 0 {
		return nil
	}

	// Use CountAll to efficiently validate library IDs exist
	count, err := s.ds.Library().CountAll(ctx, model.QueryOptions{
		Filters: squirrel.Eq{"id": libraryIDs},
	})
	if err != nil {
		return fmt.Errorf("error validating library IDs: %w", err)
	}

	if int(count) != len(libraryIDs) {
		return fmt.Errorf("%w: one or more library IDs are invalid", model.ErrValidation)
	}

	return nil
}

var scanWaitInterval = time.Second

func (r *libraryRepositoryWrapper) triggerScan(ctx context.Context, lib *model.Library, action string) {
	// Runs in its own goroutine and outlives the HTTP request
	ctx = context.WithoutCancel(ctx)

	// A running scan loaded the libraries before this change, and would reject a new request
	for {
		status, err := r.scanner.Status(ctx)
		if err != nil || !status.Scanning {
			break
		}
		time.Sleep(scanWaitInterval)
	}

	log.Info(ctx, fmt.Sprintf("Triggering scan for %s library", action), "libraryID", lib.ID, "name", lib.Name, "path", lib.Path)
	start := time.Now()
	warnings, err := r.scanner.ScanAll(ctx, false) // Quick scan: the scanner rescans libraries with a changed PID config in full
	if errors.Is(err, model.ErrAlreadyScanning) {
		log.Debug(ctx, "Scan already running, it covers this change", "libraryID", lib.ID, "name", lib.Name)
	} else if err != nil {
		log.Error(ctx, fmt.Sprintf("Error scanning %s library", action), "libraryID", lib.ID, "name", lib.Name, err)
	} else {
		log.Info(ctx, fmt.Sprintf("Scan completed for %s library", action), "libraryID", lib.ID, "name", lib.Name, "warnings", len(warnings), "elapsed", time.Since(start))
	}
}