// Package history provides a persistent, size-bounded clipboard history store.
//
// Entries are kept in memory as a ring buffer and flushed to a JSON file so the
// `clip-sync history` command can read them even when the daemon is not running.
package history

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

// Entry is a single clipboard history record.
type Entry struct {
	Text   string `json:"text"`
	Origin string `json:"origin"`
	Ts     int64  `json:"ts"` // nanosecond timestamp
}

// Store is a thread-safe, persistent history store.
type Store struct {
	mu      sync.Mutex
	path    string
	max     int
	entries []Entry
}

// New creates a history store that persists to the given file path, keeping at
// most max entries. If max <= 0, a sensible default is used.
func New(path string, max int) *Store {
	if max <= 0 {
		max = 50
	}
	s := &Store{path: path, max: max}
	s.load()
	return s
}

// Append adds an entry, trimming the store to max entries and persisting it.
func (s *Store) Append(e Entry) {
	if e.Text == "" {
		return
	}
	s.mu.Lock()
	defer s.mu.Unlock()

	// Skip exact duplicates of the most recent entry.
	if len(s.entries) > 0 && s.entries[len(s.entries)-1].Text == e.Text {
		return
	}

	s.entries = append(s.entries, e)
	if len(s.entries) > s.max {
		s.entries = s.entries[len(s.entries)-s.max:]
	}
	s.save()
}

// List returns a copy of the history, oldest first.
func (s *Store) List() []Entry {
	s.mu.Lock()
	defer s.mu.Unlock()
	out := make([]Entry, len(s.entries))
	copy(out, s.entries)
	return out
}

func (s *Store) load() {
	data, err := os.ReadFile(s.path)
	if err != nil {
		return
	}
	_ = json.Unmarshal(data, &s.entries)
	if len(s.entries) > s.max {
		s.entries = s.entries[len(s.entries)-s.max:]
	}
}

func (s *Store) save() {
	data, err := json.MarshalIndent(s.entries, "", "  ")
	if err != nil {
		return
	}
	if err := os.MkdirAll(filepath.Dir(s.path), 0755); err != nil {
		return
	}
	tmp := s.path + ".tmp"
	if err := os.WriteFile(tmp, data, 0644); err != nil {
		return
	}
	_ = os.Rename(tmp, s.path)
}

// DefaultPath returns the default history file location.
func DefaultPath() (string, error) {
	home, err := os.UserHomeDir()
	if err != nil {
		return "", fmt.Errorf("history: cannot find home directory: %w", err)
	}
	return filepath.Join(home, ".config", "clip-sync", "history.json"), nil
}