package config

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

// ModelsConfigStore manages persistence of model configuration to a JSON file.
type ModelsConfigStore struct {
	mu     sync.RWMutex
	path   string
	config *ModelsConfig
}

// NewModelsConfigStore creates a ModelsConfigStore, creating an empty config file if it doesn't exist.
func NewModelsConfigStore(path string) (*ModelsConfigStore, error) {
	s := &ModelsConfigStore{
		path: path,
		config: &ModelsConfig{
			Version:   "1.0",
			Providers: make(map[string]*ProviderConfig),
			Models:    make(map[string]*ModelConfig),
			Routing:   make(map[string]*RoutingRule),
		},
	}
	if err := s.load(); err != nil {
		return nil, err
	}
	return s, nil
}

func (s *ModelsConfigStore) load() error {
	data, err := os.ReadFile(s.path)
	if err != nil {
		if os.IsNotExist(err) {
			return s.save() // Initialize empty file.
		}
		return fmt.Errorf("read model config file: %w", err)
	}
	if len(data) == 0 {
		return nil
	}
	var cfg ModelsConfig
	if err := json.Unmarshal(data, &cfg); err != nil {
		return fmt.Errorf("parse model config file: %w", err)
	}
	if cfg.Providers == nil {
		cfg.Providers = make(map[string]*ProviderConfig)
	}
	if cfg.Models == nil {
		cfg.Models = make(map[string]*ModelConfig)
	}
	if cfg.Routing == nil {
		cfg.Routing = make(map[string]*RoutingRule)
	}
	if cfg.Version == "" {
		cfg.Version = "1.0"
	}
	s.config = &cfg
	return nil
}

func (s *ModelsConfigStore) save() error {
	data, err := json.MarshalIndent(s.config, "", "  ")
	if err != nil {
		return fmt.Errorf("marshal model config: %w", err)
	}
	tmpPath := s.path + ".tmp"
	if err := os.WriteFile(tmpPath, data, 0640); err != nil {
		return fmt.Errorf("write model config file: %w", err)
	}
	return os.Rename(tmpPath, s.path)
}

// HasConfig returns true if there are any providers or models configured.
func (s *ModelsConfigStore) HasConfig() bool {
	s.mu.RLock()
	defer s.mu.RUnlock()
	return len(s.config.Providers) > 0 || len(s.config.Models) > 0
}

// ---- Providers ----

func (s *ModelsConfigStore) ListProviders() []*ProviderConfig {
	s.mu.RLock()
	defer s.mu.RUnlock()
	result := make([]*ProviderConfig, 0, len(s.config.Providers))
	for _, p := range s.config.Providers {
		result = append(result, p)
	}
	return result
}

func (s *ModelsConfigStore) GetProvider(name string) (*ProviderConfig, error) {
	s.mu.RLock()
	defer s.mu.RUnlock()
	p, ok := s.config.Providers[name]
	if !ok {
		return nil, fmt.Errorf("provider not found: %s", name)
	}
	return p, nil
}

func (s *ModelsConfigStore) SetProvider(cfg *ProviderConfig) error {
	s.mu.Lock()
	defer s.mu.Unlock()
	if cfg.Name == "" {
		return fmt.Errorf("provider name is required")
	}
	if cfg.BaseURL == "" {
		return fmt.Errorf("provider base_url is required")
	}
	cfg.UpdatedAt = time.Now()
	s.config.Providers[cfg.Name] = cfg
	return s.save()
}

func (s *ModelsConfigStore) DeleteProvider(name string) error {
	s.mu.Lock()
	defer s.mu.Unlock()
	if _, ok := s.config.Providers[name]; !ok {
		return fmt.Errorf("provider not found: %s", name)
	}
	delete(s.config.Providers, name)
	return s.save()
}

// ---- Models ----

func (s *ModelsConfigStore) ListModels() []*ModelConfig {
	s.mu.RLock()
	defer s.mu.RUnlock()
	result := make([]*ModelConfig, 0, len(s.config.Models))
	for _, m := range s.config.Models {
		result = append(result, m)
	}
	return result
}

func (s *ModelsConfigStore) GetModel(id string) (*ModelConfig, error) {
	s.mu.RLock()
	defer s.mu.RUnlock()
	m, ok := s.config.Models[id]
	if !ok {
		return nil, fmt.Errorf("model not found: %s", id)
	}
	return m, nil
}

func (s *ModelsConfigStore) SetModel(cfg *ModelConfig) error {
	s.mu.Lock()
	defer s.mu.Unlock()
	if cfg.ID == "" {
		return fmt.Errorf("model id is required")
	}
	if cfg.Provider == "" {
		return fmt.Errorf("model provider is required")
	}
	cfg.UpdatedAt = time.Now()
	if cfg.Params == nil {
		cfg.Params = make(map[string]interface{})
	}
	if cfg.Tags == nil {
		cfg.Tags = []string{}
	}
	s.config.Models[cfg.ID] = cfg
	return s.save()
}

func (s *ModelsConfigStore) DeleteModel(id string) error {
	s.mu.Lock()
	defer s.mu.Unlock()
	if _, ok := s.config.Models[id]; !ok {
		return fmt.Errorf("model not found: %s", id)
	}
	delete(s.config.Models, id)
	return s.save()
}

// ---- Routing ----

func (s *ModelsConfigStore) ListRouting() []*RoutingRule {
	s.mu.RLock()
	defer s.mu.RUnlock()
	result := make([]*RoutingRule, 0, len(s.config.Routing))
	for _, r := range s.config.Routing {
		result = append(result, r)
	}
	return result
}

func (s *ModelsConfigStore) GetRouting(purpose string) (*RoutingRule, error) {
	s.mu.RLock()
	defer s.mu.RUnlock()
	r, ok := s.config.Routing[purpose]
	if !ok {
		return nil, fmt.Errorf("routing not found: %s", purpose)
	}
	return r, nil
}

func (s *ModelsConfigStore) SetRouting(rule *RoutingRule) error {
	s.mu.Lock()
	defer s.mu.Unlock()
	if rule.Purpose == "" {
		return fmt.Errorf("routing purpose is required")
	}
	if len(rule.FallbackChain) == 0 {
		return fmt.Errorf("routing fallback_chain is required")
	}
	s.config.Routing[rule.Purpose] = rule
	return s.save()
}

func (s *ModelsConfigStore) DeleteRouting(purpose string) error {
	s.mu.Lock()
	defer s.mu.Unlock()
	if _, ok := s.config.Routing[purpose]; !ok {
		return fmt.Errorf("routing not found: %s", purpose)
	}
	delete(s.config.Routing, purpose)
	return s.save()
}

// GetConfig returns a copy of the full config (for ai-core loader compatibility).
func (s *ModelsConfigStore) GetConfig() *ModelsConfig {
	s.mu.RLock()
	defer s.mu.RUnlock()
	// Return shallow copy; callers should treat as read-only.
	return s.config
}