package services

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

	"arma3-web-server/internal/models"

	"github.com/google/uuid"
)

type ModlistManager struct {
	dir string
	mu  sync.RWMutex
}

func NewModlistManager(dataDir string) *ModlistManager {
	return &ModlistManager{
		dir: filepath.Join(dataDir, "modlists"),
	}
}

func (mm *ModlistManager) path(id string) string {
	return filepath.Join(mm.dir, id+".json")
}

func (mm *ModlistManager) List() ([]models.ModlistListItem, error) {
	mm.mu.RLock()
	defer mm.mu.RUnlock()

	entries, err := os.ReadDir(mm.dir)
	if err != nil {
		if os.IsNotExist(err) {
			return []models.ModlistListItem{}, nil
		}
		return nil, err
	}

	var items []models.ModlistListItem
	for _, e := range entries {
		if e.IsDir() || !strings.HasSuffix(e.Name(), ".json") {
			continue
		}
		data, err := os.ReadFile(filepath.Join(mm.dir, e.Name()))
		if err != nil {
			continue
		}
		var m models.Modlist
		if err := json.Unmarshal(data, &m); err != nil {
			continue
		}
		items = append(items, models.ModlistListItem{
			ID:        m.ID,
			Name:      m.Name,
			ModCount:  len(m.Mods),
			CreatedAt: m.CreatedAt,
			UpdatedAt: m.UpdatedAt,
		})
	}
	return items, nil
}

func (mm *ModlistManager) Get(id string) (*models.Modlist, error) {
	mm.mu.RLock()
	defer mm.mu.RUnlock()

	data, err := os.ReadFile(mm.path(id))
	if err != nil {
		if os.IsNotExist(err) {
			return nil, fmt.Errorf("modlist not found")
		}
		return nil, err
	}
	var m models.Modlist
	if err := json.Unmarshal(data, &m); err != nil {
		return nil, err
	}
	return &m, nil
}

func (mm *ModlistManager) Create(name string) (*models.Modlist, error) {
	mm.mu.Lock()
	defer mm.mu.Unlock()

	now := time.Now().UTC()
	m := &models.Modlist{
		ID:        uuid.New().String(),
		Name:      name,
		Mods:      []models.ModEntry{},
		CreatedAt: now,
		UpdatedAt: now,
	}

	data, err := json.MarshalIndent(m, "", "  ")
	if err != nil {
		return nil, err
	}
	if err := os.MkdirAll(mm.dir, 0755); err != nil {
		return nil, err
	}
	if err := os.WriteFile(mm.path(m.ID), data, 0644); err != nil {
		return nil, err
	}
	return m, nil
}

func (mm *ModlistManager) Update(id, name string, mods []models.ModEntry) (*models.Modlist, error) {
	mm.mu.Lock()
	defer mm.mu.Unlock()

	m, err := mm.getLocked(id)
	if err != nil {
		return nil, err
	}

	m.Name = name
	m.Mods = mods
	m.UpdatedAt = time.Now().UTC()

	data, err := json.MarshalIndent(m, "", "  ")
	if err != nil {
		return nil, err
	}
	if err := os.WriteFile(mm.path(id), data, 0644); err != nil {
		return nil, err
	}
	return m, nil
}

func (mm *ModlistManager) Delete(id string) error {
	mm.mu.Lock()
	defer mm.mu.Unlock()
	return os.Remove(mm.path(id))
}

func (mm *ModlistManager) Duplicate(id, newName string) (*models.Modlist, error) {
	mm.mu.Lock()
	defer mm.mu.Unlock()

	orig, err := mm.getLocked(id)
	if err != nil {
		return nil, err
	}

	now := time.Now().UTC()
	dup := &models.Modlist{
		ID:        uuid.New().String(),
		Name:      newName,
		Mods:      orig.Mods,
		CreatedAt: now,
		UpdatedAt: now,
	}

	data, err := json.MarshalIndent(dup, "", "  ")
	if err != nil {
		return nil, err
	}
	if err := os.WriteFile(mm.path(dup.ID), data, 0644); err != nil {
		return nil, err
	}
	return dup, nil
}

func (mm *ModlistManager) getLocked(id string) (*models.Modlist, error) {
	data, err := os.ReadFile(mm.path(id))
	if err != nil {
		if os.IsNotExist(err) {
			return nil, fmt.Errorf("modlist not found")
		}
		return nil, err
	}
	var m models.Modlist
	if err := json.Unmarshal(data, &m); err != nil {
		return nil, err
	}
	return &m, nil
}