package imager

import (
	"archive/tar"
	"compress/gzip"
	"context"
	"crypto/tls"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"strings"
	"time"

	"yizhisec.com/hsv2/forge/pkg/logger"
)

// PullOption is a functional option for configuring image pull
type PullOption func(*pullOption)

type pullOption struct {
	Proxy         string        // http or socks5 proxy
	Rename        string        // pull image and rename it
	PlainHTTP     bool          // use http instead of https
	SkipTLSVerify bool          // skip TLS certificate verification
	Username      string        // registry username for authentication
	Password      string        // registry password for authentication
	RetryTimes    int           // retry times for sync/proxy registries, default is 3
	RetryDelay    time.Duration // delay between retries, default is 2 seconds
}

// WithProxy sets the proxy for pulling images
func WithProxy(proxy string) PullOption {
	return func(o *pullOption) {
		o.Proxy = proxy
	}
}

// WithRename sets a new name for the pulled image
func WithRename(name string) PullOption {
	return func(o *pullOption) {
		o.Rename = name
	}
}

// WithPlainHTTP enables plain HTTP (no TLS)
func WithPlainHTTP() PullOption {
	return func(o *pullOption) {
		o.PlainHTTP = true
	}
}

// WithSkipTLSVerify skips TLS certificate verification
func WithSkipTLSVerify() PullOption {
	return func(o *pullOption) {
		o.SkipTLSVerify = true
	}
}

// WithAuth sets authentication credentials
func WithAuth(username, password string) PullOption {
	return func(o *pullOption) {
		o.Username = username
		o.Password = password
	}
}

// WithRetry sets the retry times for pulling images
func WithRetry(times int) PullOption {
	return func(o *pullOption) {
		if times < 0 {
			times = 0
		}
		o.RetryTimes = times
	}
}

// WithRetryDelay sets the delay between retries
func WithRetryDelay(delay time.Duration) PullOption {
	return func(o *pullOption) {
		o.RetryDelay = delay
	}
}

// manifestV2 represents Docker manifest v2 schema
type manifestV2 struct {
	SchemaVersion int    `json:"schemaVersion"`
	MediaType     string `json:"mediaType"`
	Config        struct {
		MediaType string `json:"mediaType"`
		Size      int64  `json:"size"`
		Digest    string `json:"digest"`
	} `json:"config"`
	Layers []struct {
		MediaType string `json:"mediaType"`
		Size      int64  `json:"size"`
		Digest    string `json:"digest"`
	} `json:"layers"`
}

// imageReference parses image reference into registry, repository, and tag
type imageReference struct {
	Registry   string
	Repository string
	Tag        string
}

// parseImageReference parses an image name into its components
func parseImageReference(name string) (*imageReference, error) {
	ref := &imageReference{
		Tag: "latest",
	}

	// First, split by / to separate registry from repository
	// This handles cases like localhost:5000/myimage:tag
	slashParts := strings.SplitN(name, "/", 2)

	var registryPart, repoPart string

	if len(slashParts) == 1 {
		// No slash, it's just image:tag (e.g., alpine:3.19)
		repoPart = slashParts[0]
		ref.Registry = "registry-1.docker.io"
	} else {
		// Has slash, check if first part is a registry
		// Registry contains . or : (for host:port)
		if strings.Contains(slashParts[0], ".") || strings.Contains(slashParts[0], ":") {
			// First part is a registry
			registryPart = slashParts[0]
			repoPart = slashParts[1]
			ref.Registry = registryPart
		} else {
			// First part is namespace (e.g., library/alpine)
			repoPart = name
			ref.Registry = "registry-1.docker.io"
		}
	}

	// Now parse the repository and tag from repoPart
	// Split on last : to get tag (in case repository name contains /)
	lastColon := strings.LastIndex(repoPart, ":")
	if lastColon > 0 {
		ref.Repository = repoPart[:lastColon]
		ref.Tag = repoPart[lastColon+1:]
	} else {
		ref.Repository = repoPart
	}

	// For docker.io, add library/ prefix if no namespace
	if ref.Registry == "registry-1.docker.io" && !strings.Contains(ref.Repository, "/") {
		ref.Repository = "library/" + ref.Repository
	}

	return ref, nil
}

// PullImage pulls an OCI image using HTTP requests and saves it as a tar archive
func PullImage(ctx context.Context, name string, store io.Writer, opts ...PullOption) error {
	options := &pullOption{
		RetryTimes: 3,               // default retry times
		RetryDelay: 2 * time.Second, // default retry delay
	}
	for _, opt := range opts {
		opt(options)
	}

	logger.Debug("Pulling image: %s with options: %+v", name, options)

	// Parse image reference
	ref, err := parseImageReference(name)
	if err != nil {
		return fmt.Errorf("failed to parse image reference: %w", err)
	}

	logger.Debug("Parsed image reference: registry=%s, repository=%s, tag=%s", ref.Registry, ref.Repository, ref.Tag)

	// Create HTTP client
	client := createHTTPClient(options)

	// Retry logic for sync/proxy registries
	var lastErr error
	for attempt := 0; attempt <= options.RetryTimes; attempt++ {
		if attempt > 0 {
			logger.Debug("Retry attempt %d/%d for image: %s", attempt, options.RetryTimes, name)
			select {
			case <-ctx.Done():
				return ctx.Err()
			case <-time.After(options.RetryDelay):
				// Continue after delay
			}
		}

		// Get auth token if needed
		token, err := getAuthToken(ctx, client, ref, options)
		if err != nil {
			lastErr = fmt.Errorf("failed to get auth token: %w", err)
			logger.Debug("Attempt %d failed: %v", attempt+1, lastErr)
			continue
		}

		// Get manifest
		manifest, err := getManifest(ctx, client, ref, token, options)
		if err != nil {
			lastErr = fmt.Errorf("failed to get manifest: %w", err)
			logger.Debug("Attempt %d failed: %v", attempt+1, lastErr)
			continue
		}

		logger.Debug("Got manifest with %d layers", len(manifest.Layers))

		// Download and create tar archive
		if err := createImageTar(ctx, client, ref, manifest, token, store, name, options); err != nil {
			lastErr = fmt.Errorf("failed to create image tar: %w", err)
			logger.Debug("Attempt %d failed: %v", attempt+1, lastErr)
			continue
		}

		// Success!
		logger.Info("Successfully pulled image: %s", name)
		return nil
	}

	// All retries exhausted
	if options.RetryTimes > 0 {
		return fmt.Errorf("failed to pull image after %d retries: %w", options.RetryTimes+1, lastErr)
	}
	return lastErr
}

// createHTTPClient creates an HTTP client with the given options
func createHTTPClient(options *pullOption) *http.Client {
	client := &http.Client{}

	// Configure TLS
	if options.SkipTLSVerify {
		transport := &http.Transport{
			TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
		}
		client.Transport = transport
	}

	// Configure proxy
	if options.Proxy != "" {
		proxyURL, err := url.Parse(options.Proxy)
		if err == nil {
			if client.Transport == nil {
				client.Transport = &http.Transport{}
			}
			if transport, ok := client.Transport.(*http.Transport); ok {
				transport.Proxy = http.ProxyURL(proxyURL)
			}
		}
	}

	return client
}

// getAuthToken gets authentication token from registry
func getAuthToken(ctx context.Context, client *http.Client, ref *imageReference, options *pullOption) (string, error) {
	// Try to access registry API v2 to get auth challenge
	scheme := "https"
	if options.PlainHTTP {
		scheme = "http"
	}

	apiURL := fmt.Sprintf("%s://%s/v2/", scheme, ref.Registry)
	req, err := http.NewRequestWithContext(ctx, "GET", apiURL, nil)
	if err != nil {
		return "", err
	}

	// Add basic auth if provided
	if options.Username != "" && options.Password != "" {
		req.SetBasicAuth(options.Username, options.Password)
	}

	resp, err := client.Do(req)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()

	// If 200 OK, no auth needed
	if resp.StatusCode == http.StatusOK {
		return "", nil
	}

	// Check for WWW-Authenticate header
	authHeader := resp.Header.Get("WWW-Authenticate")
	if authHeader == "" {
		return "", nil
	}

	// Parse auth challenge
	token, err := fetchToken(ctx, client, authHeader, ref, options)
	if err != nil {
		return "", err
	}

	return token, nil
}

// fetchToken fetches authentication token from auth server
func fetchToken(ctx context.Context, client *http.Client, authHeader string, ref *imageReference, options *pullOption) (string, error) {
	// Parse WWW-Authenticate header
	// Format: Bearer realm="https://auth.docker.io/token",service="registry.docker.io",scope="repository:library/alpine:pull"
	if !strings.HasPrefix(authHeader, "Bearer ") {
		return "", nil
	}

	params := make(map[string]string)
	parts := strings.Split(authHeader[7:], ",")
	for _, part := range parts {
		part = strings.TrimSpace(part)
		idx := strings.Index(part, "=")
		if idx > 0 {
			key := part[:idx]
			value := strings.Trim(part[idx+1:], "\"")
			params[key] = value
		}
	}

	realm, ok := params["realm"]
	if !ok {
		return "", fmt.Errorf("no realm in auth header")
	}

	// Build token URL
	tokenURL := realm
	if service, ok := params["service"]; ok {
		tokenURL += "?service=" + url.QueryEscape(service)
	}
	scope := fmt.Sprintf("repository:%s:pull", ref.Repository)
	if params["scope"] != "" {
		scope = params["scope"]
	}
	tokenURL += "&scope=" + url.QueryEscape(scope)

	req, err := http.NewRequestWithContext(ctx, "GET", tokenURL, nil)
	if err != nil {
		return "", err
	}

	// Add basic auth if provided
	if options.Username != "" && options.Password != "" {
		req.SetBasicAuth(options.Username, options.Password)
	}

	resp, err := client.Do(req)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return "", fmt.Errorf("failed to get token: %s", resp.Status)
	}

	var tokenResp struct {
		Token string `json:"token"`
	}
	if err := json.NewDecoder(resp.Body).Decode(&tokenResp); err != nil {
		return "", err
	}

	return tokenResp.Token, nil
}

// getManifest fetches the image manifest
func getManifest(ctx context.Context, client *http.Client, ref *imageReference, token string, options *pullOption) (*manifestV2, error) {
	scheme := "https"
	if options.PlainHTTP {
		scheme = "http"
	}

	manifestURL := fmt.Sprintf("%s://%s/v2/%s/manifests/%s", scheme, ref.Registry, ref.Repository, ref.Tag)
	req, err := http.NewRequestWithContext(ctx, "GET", manifestURL, nil)
	if err != nil {
		return nil, err
	}

	// Set accept headers for manifest v2 (add both types)
	req.Header.Add("Accept", "application/vnd.docker.distribution.manifest.v2+json")
	req.Header.Add("Accept", "application/vnd.oci.image.manifest.v1+json")
	req.Header.Add("Accept", "application/vnd.docker.distribution.manifest.list.v2+json")

	if token != "" {
		req.Header.Set("Authorization", "Bearer "+token)
	}

	logger.Debug("Fetching manifest from: %s", manifestURL)
	resp, err := client.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		logger.Debug("Manifest request failed: %s, body: %s", resp.Status, string(body))
		return nil, fmt.Errorf("failed to get manifest: %s", resp.Status)
	}

	contentType := resp.Header.Get("Content-Type")
	logger.Debug("Manifest Content-Type: %s", contentType)

	// Read response body
	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, err
	}

	// Check if it's a manifest list (multi-arch)
	if strings.Contains(contentType, "manifest.list") || strings.Contains(contentType, "image.index") {
		// Parse manifest list and select amd64/linux
		var manifestList struct {
			SchemaVersion int `json:"schemaVersion"`
			Manifests     []struct {
				Digest   string `json:"digest"`
				Platform struct {
					Architecture string `json:"architecture"`
					OS           string `json:"os"`
				} `json:"platform"`
			} `json:"manifests"`
		}
		if err := json.Unmarshal(body, &manifestList); err != nil {
			return nil, fmt.Errorf("failed to parse manifest list: %w", err)
		}

		logger.Debug("Found manifest list with %d manifests", len(manifestList.Manifests))

		// Find amd64/linux manifest
		var targetDigest string
		for _, m := range manifestList.Manifests {
			logger.Debug("Checking manifest: arch=%s, os=%s, digest=%s",
				m.Platform.Architecture, m.Platform.OS, m.Digest)
			if m.Platform.Architecture == "amd64" && m.Platform.OS == "linux" {
				targetDigest = m.Digest
				break
			}
		}
		if targetDigest == "" && len(manifestList.Manifests) > 0 {
			// Fallback to first manifest with known platform
			for _, m := range manifestList.Manifests {
				if m.Platform.Architecture != "unknown" && m.Platform.OS != "unknown" {
					targetDigest = m.Digest
					logger.Debug("Using fallback manifest: arch=%s, os=%s",
						m.Platform.Architecture, m.Platform.OS)
					break
				}
			}
		}
		if targetDigest == "" {
			return nil, fmt.Errorf("no suitable manifest found in manifest list")
		}

		logger.Debug("Selected manifest digest: %s", targetDigest)
		// Fetch the actual manifest by digest
		return getManifestByDigest(ctx, client, ref, targetDigest, token, options)
	}

	var manifest manifestV2
	if err := json.Unmarshal(body, &manifest); err != nil {
		return nil, fmt.Errorf("failed to parse manifest: %w", err)
	}

	logger.Debug("Parsed manifest: schemaVersion=%d, config.digest=%s, layers=%d",
		manifest.SchemaVersion, manifest.Config.Digest, len(manifest.Layers))

	return &manifest, nil
}

// getManifestByDigest fetches a manifest by its digest
func getManifestByDigest(ctx context.Context, client *http.Client, ref *imageReference, digest, token string, options *pullOption) (*manifestV2, error) {
	scheme := "https"
	if options.PlainHTTP {
		scheme = "http"
	}

	manifestURL := fmt.Sprintf("%s://%s/v2/%s/manifests/%s", scheme, ref.Registry, ref.Repository, digest)
	req, err := http.NewRequestWithContext(ctx, "GET", manifestURL, nil)
	if err != nil {
		return nil, err
	}

	req.Header.Add("Accept", "application/vnd.docker.distribution.manifest.v2+json")
	req.Header.Add("Accept", "application/vnd.oci.image.manifest.v1+json")

	if token != "" {
		req.Header.Set("Authorization", "Bearer "+token)
	}

	resp, err := client.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("failed to get manifest by digest: %s", resp.Status)
	}

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, err
	}

	var manifest manifestV2
	if err := json.Unmarshal(body, &manifest); err != nil {
		return nil, fmt.Errorf("failed to parse manifest: %w", err)
	}

	return &manifest, nil
}

// createImageTar downloads layers and creates a Docker-compatible tar archive
func createImageTar(ctx context.Context, client *http.Client, ref *imageReference, manifest *manifestV2, token string, store io.Writer, imageName string, options *pullOption) error {
	// Create tar writer
	tw := tar.NewWriter(store)
	defer tw.Close()

	scheme := "https"
	if options.PlainHTTP {
		scheme = "http"
	}

	// Download config blob
	logger.Debug("Downloading config blob: %s", manifest.Config.Digest)
	configBlob, err := downloadBlob(ctx, client, scheme, ref.Registry, ref.Repository, manifest.Config.Digest, token)
	if err != nil {
		return fmt.Errorf("failed to download config: %w", err)
	}

	// Write config as json file
	configFileName := strings.TrimPrefix(manifest.Config.Digest, "sha256:") + ".json"
	if err := writeTarEntry(tw, configFileName, configBlob); err != nil {
		return err
	}

	// Download and write each layer
	var layerFiles []string
	for i, layer := range manifest.Layers {
		logger.Debug("Downloading layer %d/%d: %s", i+1, len(manifest.Layers), layer.Digest)
		layerBlob, err := downloadBlob(ctx, client, scheme, ref.Registry, ref.Repository, layer.Digest, token)
		if err != nil {
			return fmt.Errorf("failed to download layer %s: %w", layer.Digest, err)
		}

		layerFileName := strings.TrimPrefix(layer.Digest, "sha256:") + "/layer.tar"
		layerFiles = append(layerFiles, layerFileName)

		if err := writeTarEntry(tw, layerFileName, layerBlob); err != nil {
			return err
		}
	}

	// Create manifest.json for Docker compatibility
	if options.Rename != "" {
		imageName = options.Rename
	}

	manifestJSON := []map[string]interface{}{
		{
			"Config":   configFileName,
			"RepoTags": []string{imageName},
			"Layers":   layerFiles,
		},
	}

	manifestData, err := json.Marshal(manifestJSON)
	if err != nil {
		return err
	}

	if err := writeTarEntry(tw, "manifest.json", manifestData); err != nil {
		return err
	}

	// Create repositories file (legacy)
	repositories := make(map[string]map[string]string)
	repositories[imageName] = map[string]string{ref.Tag: strings.TrimPrefix(manifest.Config.Digest, "sha256:")[:12]}
	reposData, err := json.Marshal(repositories)
	if err != nil {
		return err
	}

	if err := writeTarEntry(tw, "repositories", reposData); err != nil {
		return err
	}

	return nil
}

// downloadBlob downloads a blob from registry
func downloadBlob(ctx context.Context, client *http.Client, scheme, registry, repository, digest, token string) ([]byte, error) {
	blobURL := fmt.Sprintf("%s://%s/v2/%s/blobs/%s", scheme, registry, repository, digest)
	req, err := http.NewRequestWithContext(ctx, "GET", blobURL, nil)
	if err != nil {
		return nil, err
	}

	if token != "" {
		req.Header.Set("Authorization", "Bearer "+token)
	}

	resp, err := client.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("failed to download blob: %s", resp.Status)
	}

	// Check if content is gzipped
	var reader io.Reader = resp.Body
	if resp.Header.Get("Content-Type") == "application/vnd.docker.image.rootfs.diff.tar.gzip" ||
		strings.Contains(resp.Header.Get("Content-Encoding"), "gzip") {
		gzReader, err := gzip.NewReader(resp.Body)
		if err == nil {
			defer gzReader.Close()
			reader = gzReader
		}
	}

	return io.ReadAll(reader)
}

// writeTarEntry writes a file entry to tar archive
func writeTarEntry(tw *tar.Writer, name string, data []byte) error {
	hdr := &tar.Header{
		Name: name,
		Mode: 0644,
		Size: int64(len(data)),
	}

	if err := tw.WriteHeader(hdr); err != nil {
		return err
	}

	if _, err := tw.Write(data); err != nil {
		return err
	}

	return nil
}