package ticket

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

	"github.com/google/uuid"
)

const (
	timeEntriesFileName = "time_entries.json"
	activeTimerFileName = "active_timer.json"
)

// JSONTimeStore persists time entries and the active timer under DataDir.
type JSONTimeStore struct {
	dataDir string
	mu      sync.Mutex
}

// NewJSONTimeStore creates a time store rooted at dataDir.
func NewJSONTimeStore(dataDir string) *JSONTimeStore {
	return &JSONTimeStore{dataDir: dataDir}
}

func (s *JSONTimeStore) entriesPath() string {
	return filepath.Join(s.dataDir, timeEntriesFileName)
}

func (s *JSONTimeStore) timerPath() string {
	return filepath.Join(s.dataDir, activeTimerFileName)
}

// List returns all time entries.
func (s *JSONTimeStore) List() ([]TimeEntry, error) {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.readUnlocked()
}

// ListByTicket returns entries for one ticket.
func (s *JSONTimeStore) ListByTicket(ticketID string) ([]TimeEntry, error) {
	all, err := s.List()
	if err != nil {
		return nil, err
	}
	out := make([]TimeEntry, 0)
	for _, e := range all {
		if e.TicketID == ticketID {
			out = append(out, e)
		}
	}
	return out, nil
}

// Create adds a time entry, assigning an ID if missing.
func (s *JSONTimeStore) Create(e TimeEntry) (TimeEntry, error) {
	s.mu.Lock()
	defer s.mu.Unlock()

	if e.TicketID == "" {
		return TimeEntry{}, fmt.Errorf("ticketId is required")
	}
	if e.Duration <= 0 && !e.End.IsZero() && !e.Start.IsZero() {
		e.Duration = e.End.Sub(e.Start)
	}
	if e.Duration <= 0 {
		return TimeEntry{}, fmt.Errorf("duration must be positive")
	}
	if e.ID == "" {
		e.ID = uuid.NewString()
	}
	if e.Source == "" {
		e.Source = SourceManual
	}
	if e.Start.IsZero() {
		e.Start = time.Now().UTC()
	}
	if e.End.IsZero() {
		e.End = e.Start.Add(e.Duration)
	}

	entries, err := s.readUnlocked()
	if err != nil {
		return TimeEntry{}, err
	}
	entries = append(entries, e)
	if err := s.writeUnlocked(entries); err != nil {
		return TimeEntry{}, err
	}
	return e, nil
}

// Update replaces an existing time entry by ID.
func (s *JSONTimeStore) Update(e TimeEntry) error {
	s.mu.Lock()
	defer s.mu.Unlock()

	if e.ID == "" {
		return fmt.Errorf("time entry id is required")
	}
	if e.Duration <= 0 {
		return fmt.Errorf("duration must be positive")
	}
	if e.Start.IsZero() {
		e.Start = time.Now().UTC()
	}
	e.End = e.Start.Add(e.Duration)

	entries, err := s.readUnlocked()
	if err != nil {
		return err
	}
	found := false
	for i := range entries {
		if entries[i].ID == e.ID {
			entries[i] = e
			found = true
			break
		}
	}
	if !found {
		return fmt.Errorf("time entry %s: not found", e.ID)
	}
	return s.writeUnlocked(entries)
}

// Delete removes a time entry by ID.
func (s *JSONTimeStore) Delete(id string) error {
	s.mu.Lock()
	defer s.mu.Unlock()

	entries, err := s.readUnlocked()
	if err != nil {
		return err
	}
	out := make([]TimeEntry, 0, len(entries))
	found := false
	for _, e := range entries {
		if e.ID == id {
			found = true
			continue
		}
		out = append(out, e)
	}
	if !found {
		return fmt.Errorf("time entry %s: not found", id)
	}
	return s.writeUnlocked(out)
}

// DeleteByProject removes all time entries for a project.
func (s *JSONTimeStore) DeleteByProject(projectID string) error {
	s.mu.Lock()
	defer s.mu.Unlock()

	if projectID == "" {
		return fmt.Errorf("projectId is required")
	}
	entries, err := s.readUnlocked()
	if err != nil {
		return err
	}
	out := make([]TimeEntry, 0, len(entries))
	for _, e := range entries {
		if e.ProjectID == projectID {
			continue
		}
		out = append(out, e)
	}
	return s.writeUnlocked(out)
}

// SumByTicket returns total duration for a ticket.
func (s *JSONTimeStore) SumByTicket(ticketID string) (time.Duration, error) {
	entries, err := s.ListByTicket(ticketID)
	if err != nil {
		return 0, err
	}
	var sum time.Duration
	for _, e := range entries {
		sum += e.Duration
	}
	return sum, nil
}

// LoadActiveTimer returns the running timer, or nil if none.
func (s *JSONTimeStore) LoadActiveTimer() (*ActiveTimer, error) {
	s.mu.Lock()
	defer s.mu.Unlock()

	data, err := os.ReadFile(s.timerPath())
	if err != nil {
		if os.IsNotExist(err) {
			return nil, nil
		}
		return nil, fmt.Errorf("read active timer: %w", err)
	}
	if len(data) == 0 {
		return nil, nil
	}
	var t ActiveTimer
	if err := json.Unmarshal(data, &t); err != nil {
		return nil, fmt.Errorf("parse active timer: %w", err)
	}
	if t.TicketID == "" {
		return nil, nil
	}
	return &t, nil
}

// SaveActiveTimer writes the active timer, or removes the file when t is nil.
func (s *JSONTimeStore) SaveActiveTimer(t *ActiveTimer) error {
	s.mu.Lock()
	defer s.mu.Unlock()

	path := s.timerPath()
	if t == nil {
		if err := os.Remove(path); err != nil && !os.IsNotExist(err) {
			return fmt.Errorf("clear active timer: %w", err)
		}
		return nil
	}
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		return fmt.Errorf("create data dir: %w", err)
	}
	data, err := json.MarshalIndent(t, "", "  ")
	if err != nil {
		return fmt.Errorf("marshal active timer: %w", err)
	}
	data = append(data, '\n')
	tmp, err := os.CreateTemp(filepath.Dir(path), "timer-*.tmp")
	if err != nil {
		return fmt.Errorf("create temp timer: %w", err)
	}
	tmpName := tmp.Name()
	defer func() { _ = os.Remove(tmpName) }()
	if _, err := tmp.Write(data); err != nil {
		_ = tmp.Close()
		return fmt.Errorf("write temp timer: %w", err)
	}
	if err := tmp.Close(); err != nil {
		return fmt.Errorf("close temp timer: %w", err)
	}
	if err := os.Rename(tmpName, path); err != nil {
		return fmt.Errorf("rename timer: %w", err)
	}
	return nil
}

func (s *JSONTimeStore) readUnlocked() ([]TimeEntry, error) {
	path := s.entriesPath()
	data, err := os.ReadFile(path)
	if err != nil {
		if os.IsNotExist(err) {
			return []TimeEntry{}, nil
		}
		return nil, fmt.Errorf("read %s: %w", path, err)
	}
	if len(data) == 0 {
		return []TimeEntry{}, nil
	}
	var entries []TimeEntry
	if err := json.Unmarshal(data, &entries); err != nil {
		return nil, fmt.Errorf("parse %s: %w", path, err)
	}
	if entries == nil {
		entries = []TimeEntry{}
	}
	return entries, nil
}

func (s *JSONTimeStore) writeUnlocked(entries []TimeEntry) error {
	path := s.entriesPath()
	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
		return fmt.Errorf("create data dir: %w", err)
	}
	data, err := json.MarshalIndent(entries, "", "  ")
	if err != nil {
		return fmt.Errorf("marshal time entries: %w", err)
	}
	data = append(data, '\n')
	tmp, err := os.CreateTemp(filepath.Dir(path), "time-*.tmp")
	if err != nil {
		return fmt.Errorf("create temp file: %w", err)
	}
	tmpName := tmp.Name()
	defer func() { _ = os.Remove(tmpName) }()
	if _, err := tmp.Write(data); err != nil {
		_ = tmp.Close()
		return fmt.Errorf("write temp file: %w", err)
	}
	if err := tmp.Close(); err != nil {
		return fmt.Errorf("close temp file: %w", err)
	}
	if err := os.Rename(tmpName, path); err != nil {
		return fmt.Errorf("rename temp to %s: %w", path, err)
	}
	return nil
}