package state

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"sync"
	"time"
)

// ActivityInfo holds information about a downloaded activity
type ActivityInfo struct {
	ID               int64     `json:"id"`
	Name             string    `json:"name"`
	Date             time.Time `json:"date"`
	FilePath         string    `json:"file_path"`
	DownloadedAt     time.Time `json:"downloaded_at"`
	SportType        string    `json:"sport_type,omitempty"`
}

// State manages the persistent state of downloaded activities
type State struct {
	DownloadedActivities map[int64]ActivityInfo `json:"downloaded_activities"`
	LastCheck            time.Time              `json:"last_check"`
	TotalDownloaded      int                    `json:"total_downloaded"`

	filePath string
	mu       sync.RWMutex
}

// New creates a new State instance
func New(filePath string) *State {
	return &State{
		DownloadedActivities: make(map[int64]ActivityInfo),
		LastCheck:            time.Time{},
		TotalDownloaded:      0,
		filePath:             filePath,
	}
}

// Load loads state from JSON file
func (s *State) Load() error {
	s.mu.Lock()
	defer s.mu.Unlock()

	// Check if file exists
	if _, err := os.Stat(s.filePath); os.IsNotExist(err) {
		// File doesn't exist, start with empty state
		return nil
	}

	// Read file
	data, err := os.ReadFile(s.filePath)
	if err != nil {
		return fmt.Errorf("failed to read state file: %w", err)
	}

	// Unmarshal JSON
	if err := json.Unmarshal(data, s); err != nil {
		// Try to backup corrupted file
		backupPath := s.filePath + ".backup"
		_ = os.WriteFile(backupPath, data, 0600)
		return fmt.Errorf("failed to unmarshal state file (backed up to %s): %w", backupPath, err)
	}

	return nil
}

// Save saves state to JSON file
func (s *State) Save() error {
	s.mu.RLock()
	defer s.mu.RUnlock()

	// Create directory if it doesn't exist
	dir := filepath.Dir(s.filePath)
	if err := os.MkdirAll(dir, 0755); err != nil {
		return fmt.Errorf("failed to create state directory: %w", err)
	}

	// Marshal to JSON
	data, err := json.MarshalIndent(s, "", "  ")
	if err != nil {
		return fmt.Errorf("failed to marshal state: %w", err)
	}

	// Write to temporary file first (atomic write)
	tmpFile := s.filePath + ".tmp"
	if err := os.WriteFile(tmpFile, data, 0600); err != nil {
		return fmt.Errorf("failed to write temporary state file: %w", err)
	}

	// Rename temporary file to actual file (atomic operation)
	if err := os.Rename(tmpFile, s.filePath); err != nil {
		return fmt.Errorf("failed to rename temporary state file: %w", err)
	}

	return nil
}

// IsDownloaded checks if an activity has already been downloaded
func (s *State) IsDownloaded(activityID int64) bool {
	s.mu.RLock()
	defer s.mu.RUnlock()

	_, exists := s.DownloadedActivities[activityID]
	return exists
}

// MarkDownloaded marks an activity as downloaded
func (s *State) MarkDownloaded(info ActivityInfo) error {
	s.mu.Lock()
	defer s.mu.Unlock()

	s.DownloadedActivities[info.ID] = info
	s.TotalDownloaded++
	s.LastCheck = time.Now()

	// Save state after marking downloaded
	return s.save()
}

// UpdateLastCheck updates the last check timestamp
func (s *State) UpdateLastCheck() error {
	s.mu.Lock()
	defer s.mu.Unlock()

	s.LastCheck = time.Now()
	return s.save()
}

// GetStats returns statistics about downloaded activities
func (s *State) GetStats() (totalDownloaded int, lastCheck time.Time) {
	s.mu.RLock()
	defer s.mu.RUnlock()

	return s.TotalDownloaded, s.LastCheck
}

// save is an internal method that saves without locking (assumes lock is held)
func (s *State) save() error {
	// Create directory if it doesn't exist
	dir := filepath.Dir(s.filePath)
	if err := os.MkdirAll(dir, 0755); err != nil {
		return fmt.Errorf("failed to create state directory: %w", err)
	}

	// Marshal to JSON
	data, err := json.MarshalIndent(s, "", "  ")
	if err != nil {
		return fmt.Errorf("failed to marshal state: %w", err)
	}

	// Write to temporary file first (atomic write)
	tmpFile := s.filePath + ".tmp"
	if err := os.WriteFile(tmpFile, data, 0600); err != nil {
		return fmt.Errorf("failed to write temporary state file: %w", err)
	}

	// Rename temporary file to actual file (atomic operation)
	if err := os.Rename(tmpFile, s.filePath); err != nil {
		return fmt.Errorf("failed to rename temporary state file: %w", err)
	}

	return nil
}