package registry

import (
	"context"
	_ "embed"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"sync"
	"time"

	log "github.com/sirupsen/logrus"
)

const (
	modelsFetchTimeout = 30 * time.Second
)

var modelsURLs = []string{
	"https://raw.githubusercontent.com/router-for-me/models/refs/heads/main/models.json",
	"https://models.router-for.me/models.json",
}

//go:embed models/models.json
var embeddedModelsJSON []byte

type modelStore struct {
	mu   sync.RWMutex
	data *staticModelsJSON
}

var modelsCatalogStore = &modelStore{}

var updaterOnce sync.Once

func init() {
	// Load embedded data as fallback on startup.
	if err := loadModelsFromBytes(embeddedModelsJSON, "embed"); err != nil {
		panic(fmt.Sprintf("registry: failed to parse embedded models.json: %v", err))
	}
}

// StartModelsUpdater runs a one-time models refresh on startup.
// It blocks until the startup fetch attempt finishes so service initialization
// can wait for the refreshed catalog before registering auth-backed models.
// Safe to call multiple times; only one refresh will run.
func StartModelsUpdater(ctx context.Context) {
	updaterOnce.Do(func() {
		runModelsUpdater(ctx)
	})
}

func runModelsUpdater(ctx context.Context) {
	// Try network fetch once on startup, then stop.
	// Periodic refresh is disabled - models are only refreshed at startup.
	tryRefreshModels(ctx)
}

func tryRefreshModels(ctx context.Context) {
	client := &http.Client{Timeout: modelsFetchTimeout}
	for _, url := range modelsURLs {
		reqCtx, cancel := context.WithTimeout(ctx, modelsFetchTimeout)
		req, err := http.NewRequestWithContext(reqCtx, "GET", url, nil)
		if err != nil {
			cancel()
			log.Debugf("models fetch request creation failed for %s: %v", url, err)
			continue
		}

		resp, err := client.Do(req)
		if err != nil {
			cancel()
			log.Debugf("models fetch failed from %s: %v", url, err)
			continue
		}

		if resp.StatusCode != 200 {
			resp.Body.Close()
			cancel()
			log.Debugf("models fetch returned %d from %s", resp.StatusCode, url)
			continue
		}

		data, err := io.ReadAll(resp.Body)
		resp.Body.Close()
		cancel()

		if err != nil {
			log.Debugf("models fetch read error from %s: %v", url, err)
			continue
		}

		if err := loadModelsFromBytes(data, url); err != nil {
			log.Warnf("models parse failed from %s: %v", url, err)
			continue
		}

		log.Infof("models updated from %s", url)
		return
	}
	log.Warn("models refresh failed from all URLs, using current data")
}

func loadModelsFromBytes(data []byte, source string) error {
	var parsed staticModelsJSON
	if err := json.Unmarshal(data, &parsed); err != nil {
		return fmt.Errorf("%s: decode models catalog: %w", source, err)
	}
	if err := validateModelsCatalog(&parsed); err != nil {
		return fmt.Errorf("%s: validate models catalog: %w", source, err)
	}

	modelsCatalogStore.mu.Lock()
	modelsCatalogStore.data = &parsed
	modelsCatalogStore.mu.Unlock()
	return nil
}

func getModels() *staticModelsJSON {
	modelsCatalogStore.mu.RLock()
	defer modelsCatalogStore.mu.RUnlock()
	return modelsCatalogStore.data
}

func validateModelsCatalog(data *staticModelsJSON) error {
	if data == nil {
		return fmt.Errorf("catalog is nil")
	}

	requiredSections := []struct {
		name   string
		models []*ModelInfo
	}{
		{name: "claude", models: data.Claude},
		{name: "gemini", models: data.Gemini},
		{name: "vertex", models: data.Vertex},
		{name: "gemini-cli", models: data.GeminiCLI},
		{name: "aistudio", models: data.AIStudio},
		{name: "codex-free", models: data.CodexFree},
		{name: "codex-team", models: data.CodexTeam},
		{name: "codex-plus", models: data.CodexPlus},
		{name: "codex-pro", models: data.CodexPro},
		{name: "qwen", models: data.Qwen},
		{name: "iflow", models: data.IFlow},
		{name: "kimi", models: data.Kimi},
	}

	for _, section := range requiredSections {
		if err := validateModelSection(section.name, section.models); err != nil {
			return err
		}
	}
	if err := validateAntigravitySection(data.Antigravity); err != nil {
		return err
	}
	return nil
}

func validateModelSection(section string, models []*ModelInfo) error {
	if len(models) == 0 {
		return fmt.Errorf("%s section is empty", section)
	}

	seen := make(map[string]struct{}, len(models))
	for i, model := range models {
		if model == nil {
			return fmt.Errorf("%s[%d] is null", section, i)
		}
		modelID := strings.TrimSpace(model.ID)
		if modelID == "" {
			return fmt.Errorf("%s[%d] has empty id", section, i)
		}
		if _, exists := seen[modelID]; exists {
			return fmt.Errorf("%s contains duplicate model id %q", section, modelID)
		}
		seen[modelID] = struct{}{}
	}
	return nil
}

func validateAntigravitySection(configs map[string]*AntigravityModelConfig) error {
	if len(configs) == 0 {
		return fmt.Errorf("antigravity section is empty")
	}

	for modelID, cfg := range configs {
		trimmedID := strings.TrimSpace(modelID)
		if trimmedID == "" {
			return fmt.Errorf("antigravity contains empty model id")
		}
		if cfg == nil {
			return fmt.Errorf("antigravity[%q] is null", trimmedID)
		}
	}
	return nil
}