package staticsite

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"path/filepath"
	"strings"
	"time"
)

// GitLabProvider implements GitProvider for GitLab repositories.
type GitLabProvider struct {
	apiBase    string // e.g., "https://gitlab.com/api/v4"
	rawBase    string // e.g., "https://gitlab.com"
	token      string
	httpClient *http.Client
}

// NewGitLabProvider creates a new GitLab provider.
// baseURL should be "https://gitlab.com" or a self-hosted GitLab URL.
func NewGitLabProvider(baseURL, token string) *GitLabProvider {
	base := strings.TrimRight(baseURL, "/")
	return &GitLabProvider{
		apiBase: base + "/api/v4",
		rawBase: base,
		token:   token,
		httpClient: &http.Client{
			Timeout: 60 * time.Second,
		},
	}
}

func (g *GitLabProvider) Name() string { return "gitlab" }

// projectPath returns the URL-encoded project path (owner/repo → owner%2Frepo).
func projectPath(owner, repo string) string {
	return url.PathEscape(owner + "/" + repo)
}

func (g *GitLabProvider) ListRepos(ctx context.Context, query string) ([]RepoInfo, error) {
	var allRepos []RepoInfo
	page := 1

	for {
		apiURL := fmt.Sprintf("%s/projects?membership=true&per_page=100&page=%d&order_by=last_activity_at", g.apiBase, page)
		if query != "" {
			apiURL += "&search=" + url.QueryEscape(query)
		}

		body, err := g.doGet(ctx, apiURL)
		if err != nil {
			return nil, fmt.Errorf("list repos: %w", err)
		}

		var projects []struct {
			PathWithNamespace string `json:"path_with_namespace"`
			Name              string `json:"name"`
			Description       string `json:"description"`
			Visibility        string `json:"visibility"`
			WebURL            string `json:"web_url"`
			Namespace         struct {
				Path string `json:"path"`
			} `json:"namespace"`
		}
		if err := json.Unmarshal(body, &projects); err != nil {
			return nil, fmt.Errorf("decode repos: %w", err)
		}

		for _, p := range projects {
			allRepos = append(allRepos, RepoInfo{
				Owner:       p.Namespace.Path,
				Name:        p.Name,
				FullName:    p.PathWithNamespace,
				Description: p.Description,
				Private:     p.Visibility != "public",
				HTMLURL:     p.WebURL,
			})
		}

		if len(projects) < 100 {
			break
		}
		page++
	}

	return allRepos, nil
}

func (g *GitLabProvider) TestConnection(ctx context.Context, owner, repo string) error {
	apiURL := fmt.Sprintf("%s/projects/%s", g.apiBase, projectPath(owner, repo))
	_, err := g.doGet(ctx, apiURL)
	return err
}

func (g *GitLabProvider) ListBranches(ctx context.Context, owner, repo string) ([]string, error) {
	var allBranches []string
	page := 1

	for {
		apiURL := fmt.Sprintf("%s/projects/%s/repository/branches?per_page=100&page=%d",
			g.apiBase, projectPath(owner, repo), page)

		body, err := g.doGet(ctx, apiURL)
		if err != nil {
			return nil, fmt.Errorf("list branches: %w", err)
		}

		var branches []struct {
			Name string `json:"name"`
		}
		if err := json.Unmarshal(body, &branches); err != nil {
			return nil, fmt.Errorf("decode branches: %w", err)
		}

		for _, b := range branches {
			allBranches = append(allBranches, b.Name)
		}

		if len(branches) < 100 {
			break
		}
		page++
	}

	return allBranches, nil
}

func (g *GitLabProvider) GetLatestCommitSHA(ctx context.Context, owner, repo, branch string) (string, error) {
	apiURL := fmt.Sprintf("%s/projects/%s/repository/branches/%s",
		g.apiBase, projectPath(owner, repo), url.PathEscape(branch))

	body, err := g.doGet(ctx, apiURL)
	if err != nil {
		return "", fmt.Errorf("get branch: %w", err)
	}

	var result struct {
		Commit struct {
			ID string `json:"id"`
		} `json:"commit"`
	}
	if err := json.Unmarshal(body, &result); err != nil {
		return "", fmt.Errorf("decode branch: %w", err)
	}

	return result.Commit.ID, nil
}

func (g *GitLabProvider) ListTree(ctx context.Context, owner, repo, branch string) ([]FolderEntry, error) {
	var allEntries []FolderEntry
	page := 1

	for {
		apiURL := fmt.Sprintf("%s/projects/%s/repository/tree?ref=%s&recursive=true&per_page=100&page=%d",
			g.apiBase, projectPath(owner, repo), url.QueryEscape(branch), page)

		body, err := g.doGet(ctx, apiURL)
		if err != nil {
			return nil, fmt.Errorf("list tree: %w", err)
		}

		var entries []struct {
			Path string `json:"path"`
			Type string `json:"type"` // "blob" or "tree"
		}
		if err := json.Unmarshal(body, &entries); err != nil {
			return nil, fmt.Errorf("decode tree: %w", err)
		}

		for _, e := range entries {
			allEntries = append(allEntries, FolderEntry{
				Path:  e.Path,
				IsDir: e.Type == "tree",
			})
		}

		if len(entries) < 100 {
			break
		}
		page++
	}

	return allEntries, nil
}

func (g *GitLabProvider) DownloadFolder(ctx context.Context, owner, repo, branch, folderPath, destDir string) error {
	entries, err := g.ListTree(ctx, owner, repo, branch)
	if err != nil {
		return fmt.Errorf("list tree: %w", err)
	}

	folderPath = strings.TrimPrefix(folderPath, "/")
	folderPath = strings.TrimSuffix(folderPath, "/")
	prefix := folderPath + "/"

	for _, entry := range entries {
		if entry.IsDir {
			continue
		}
		if !strings.HasPrefix(entry.Path, prefix) {
			continue
		}

		relativePath := strings.TrimPrefix(entry.Path, prefix)
		localPath := filepath.Join(destDir, filepath.FromSlash(relativePath))

		// GitLab raw file URL: {base}/{owner}/{repo}/-/raw/{branch}/{path}
		fileURL := fmt.Sprintf("%s/%s/%s/-/raw/%s/%s",
			g.rawBase, owner, repo, branch, entry.Path)

		if err := downloadFileHTTP(ctx, g.httpClient, fileURL, localPath, g.setAuth); err != nil {
			return fmt.Errorf("download %s: %w", relativePath, err)
		}
	}

	return nil
}

func (g *GitLabProvider) doGet(ctx context.Context, apiURL string) ([]byte, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, apiURL, nil)
	if err != nil {
		return nil, fmt.Errorf("create request: %w", err)
	}

	g.setAuth(req)
	req.Header.Set("Accept", "application/json")

	resp, err := g.httpClient.Do(req)
	if err != nil {
		return nil, fmt.Errorf("execute request: %w", err)
	}
	defer resp.Body.Close()

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("read response: %w", err)
	}

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("unexpected status %d: %s", resp.StatusCode, string(body))
	}

	return body, nil
}

func (g *GitLabProvider) setAuth(req *http.Request) {
	if g.token != "" {
		req.Header.Set("PRIVATE-TOKEN", g.token)
	}
}