package config

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

// Store loads and persists the configuration file. All methods are safe
// for concurrent use.
type Store struct {
	mu   sync.Mutex
	path string
	cfg  *Config
}

// Dir returns the CrossRelay data directory. CROSSRELAY_HOME overrides
// the default location (~/.crossrelay), which tests rely on.
func Dir() string {
	if v := strings.TrimSpace(os.Getenv("CROSSRELAY_HOME")); v != "" {
		return v
	}
	home, err := os.UserHomeDir()
	if err != nil {
		return ".crossrelay"
	}
	return filepath.Join(home, ".crossrelay")
}

// Path returns the config file location.
func Path() string { return filepath.Join(Dir(), "config.json") }

// Load reads the config file, creating defaults when it does not exist.
func Load() (*Store, error) {
	s := &Store{path: Path()}
	data, err := os.ReadFile(s.path)
	if err != nil {
		if !errors.Is(err, os.ErrNotExist) {
			return nil, err
		}
		s.cfg = DefaultConfig()
		return s, s.save()
	}
	var cfg Config
	if err := json.Unmarshal(data, &cfg); err != nil {
		return nil, fmt.Errorf("parse %s: %w", s.path, err)
	}
	cfg.normalize()
	s.cfg = &cfg
	return s, nil
}

// Config returns a snapshot of the configuration.
func (s *Store) Config() *Config {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.cfg.clone()
}

// FindProvider returns a copy of the provider with the given id.
func (s *Store) FindProvider(id string) *Provider {
	s.mu.Lock()
	defer s.mu.Unlock()
	for i := range s.cfg.Providers {
		if s.cfg.Providers[i].ID == id {
			return s.cfg.Providers[i].clone()
		}
	}
	return nil
}

// ActiveClaude returns the provider currently applied to Claude Code.
func (s *Store) ActiveClaude() *Provider {
	s.mu.Lock()
	defer s.mu.Unlock()
	if s.cfg.ActiveClaudeID == "" {
		return nil
	}
	for i := range s.cfg.Providers {
		if s.cfg.Providers[i].ID == s.cfg.ActiveClaudeID {
			return s.cfg.Providers[i].clone()
		}
	}
	return nil
}

// AddProvider validates and appends a provider.
func (s *Store) AddProvider(name, preset, baseURL, apiKey string, models Models) (*Provider, error) {
	s.mu.Lock()
	defer s.mu.Unlock()
	p, err := newProvider(name, preset, baseURL, apiKey, models)
	if err != nil {
		return nil, err
	}
	s.cfg.Providers = append(s.cfg.Providers, *p)
	if err := s.saveLocked(); err != nil {
		return nil, err
	}
	return p.clone(), nil
}

// UpdateProvider replaces a provider's editable fields. An empty apiKey
// keeps the stored key so edits never wipe it by accident.
func (s *Store) UpdateProvider(id, name, preset, baseURL, apiKey string, models Models) (*Provider, error) {
	s.mu.Lock()
	defer s.mu.Unlock()
	idx := -1
	for i := range s.cfg.Providers {
		if s.cfg.Providers[i].ID == id {
			idx = i
			break
		}
	}
	if idx < 0 {
		return nil, fmt.Errorf("provider %q not found", id)
	}
	existing := s.cfg.Providers[idx]
	if apiKey == "" {
		apiKey = existing.APIKey
	}
	updated, err := newProvider(name, preset, baseURL, apiKey, models)
	if err != nil {
		return nil, err
	}
	updated.ID = existing.ID
	updated.EnabledForClaude = existing.EnabledForClaude
	updated.CreatedAt = existing.CreatedAt
	s.cfg.Providers[idx] = *updated
	if err := s.saveLocked(); err != nil {
		return nil, err
	}
	return updated.clone(), nil
}

// DeleteProvider removes a provider and clears it when active.
func (s *Store) DeleteProvider(id string) error {
	s.mu.Lock()
	defer s.mu.Unlock()
	idx := -1
	for i := range s.cfg.Providers {
		if s.cfg.Providers[i].ID == id {
			idx = i
			break
		}
	}
	if idx < 0 {
		return fmt.Errorf("provider %q not found", id)
	}
	s.cfg.Providers = append(s.cfg.Providers[:idx], s.cfg.Providers[idx+1:]...)
	if s.cfg.ActiveClaudeID == id {
		s.cfg.ActiveClaudeID = ""
	}
	return s.saveLocked()
}

// ActivateClaude marks a provider as the one written into Claude Code's
// settings and records it as active.
func (s *Store) ActivateClaude(id string) (*Provider, error) {
	s.mu.Lock()
	defer s.mu.Unlock()
	idx := -1
	for i := range s.cfg.Providers {
		if s.cfg.Providers[i].ID == id {
			idx = i
			break
		}
	}
	if idx < 0 {
		return nil, fmt.Errorf("provider %q not found", id)
	}
	s.cfg.Providers[idx].EnabledForClaude = true
	s.cfg.ActiveClaudeID = id
	if err := s.saveLocked(); err != nil {
		return nil, err
	}
	return s.cfg.Providers[idx].clone(), nil
}

// ClearActiveClaude forgets the active provider without touching the
// provider list (used after restoring the official settings).
func (s *Store) ClearActiveClaude() error {
	s.mu.Lock()
	defer s.mu.Unlock()
	if s.cfg.ActiveClaudeID == "" {
		return nil
	}
	s.cfg.ActiveClaudeID = ""
	return s.saveLocked()
}

// SetGateway updates listener settings.
func (s *Store) SetGateway(g Gateway) error {
	g.PortMode = strings.TrimSpace(g.PortMode)
	switch g.PortMode {
	case PortModeAuto:
		g.FixedPort = 0
	case PortModeFixed:
		if g.FixedPort < 1 || g.FixedPort > 65535 {
			return errors.New("fixed port must be between 1 and 65535")
		}
	default:
		return errors.New("port mode must be \"auto\" or \"fixed\"")
	}
	s.mu.Lock()
	defer s.mu.Unlock()
	s.cfg.Gateway = g
	return s.saveLocked()
}

// SetLanguage updates the UI language.
func (s *Store) SetLanguage(lang string) error {
	if lang != LanguageChinese && lang != LanguageEnglish {
		return errors.New("language must be zh-CN or en-US")
	}
	s.mu.Lock()
	defer s.mu.Unlock()
	s.cfg.Language = lang
	return s.saveLocked()
}

func (s *Store) save() error {
	s.mu.Lock()
	defer s.mu.Unlock()
	return s.saveLocked()
}

func (s *Store) saveLocked() error {
	data, err := marshalConfig(s.cfg)
	if err != nil {
		return err
	}
	data = append(data, '\n')
	if err := os.MkdirAll(filepath.Dir(s.path), 0o700); err != nil {
		return err
	}
	tmp := s.path + ".tmp"
	if err := os.WriteFile(tmp, data, 0o600); err != nil {
		return err
	}
	if err := os.Rename(tmp, s.path); err != nil {
		_ = os.Remove(tmp)
		return err
	}
	return nil
}