// Package gitea provides a client for the Gitea API.
// It supports pull request operations, file content retrieval,
// and review submission.
package gitea

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"
	"net/url"
	"strings"
	"time"
)

// Client interacts with the Gitea API.
// A Client is safe for concurrent use by multiple goroutines.
type Client struct {
	baseURL string
	token   string
	http    *http.Client
}

// NewClient creates a new Gitea API client.
func NewClient(baseURL, token string) *Client {
	return &Client{
		baseURL: strings.TrimRight(baseURL, "/"),
		token:   token,
		http:    &http.Client{Timeout: 30 * time.Second},
	}
}

// PullRequest holds relevant PR metadata.
type PullRequest struct {
	Title string `json:"title"`
	Body  string `json:"body"`
	Head  struct {
		Sha string `json:"sha"`
		Ref string `json:"ref"`
	} `json:"head"`
}

// CommitStatus represents a single CI status entry.
type CommitStatus struct {
	Status      string `json:"status"`
	Context     string `json:"context"`
	Description string `json:"description"`
	TargetURL   string `json:"target_url"`
}

// ChangedFile represents a file modified in a PR.
type ChangedFile struct {
	Filename string `json:"filename"`
	Status   string `json:"status"`
}

// ReviewComment represents an inline comment to attach to a review.
type ReviewComment struct {
	Path        string `json:"path"`
	NewPosition int64  `json:"new_position"`
	Body        string `json:"body"`
}

// GetPullRequest fetches PR metadata.
func (c *Client) GetPullRequest(ctx context.Context, owner, repo string, number int) (*PullRequest, error) {
	reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/pulls/%d", c.baseURL, owner, repo, number)
	body, err := c.doGet(ctx, reqURL)
	if err != nil {
		return nil, fmt.Errorf("fetch PR: %w", err)
	}
	var pr PullRequest
	if err := json.Unmarshal(body, &pr); err != nil {
		return nil, fmt.Errorf("parse PR JSON: %w", err)
	}
	return &pr, nil
}

// GetPullRequestDiff fetches the unified diff for a PR.
func (c *Client) GetPullRequestDiff(ctx context.Context, owner, repo string, number int) (string, error) {
	reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/pulls/%d.diff", c.baseURL, owner, repo, number)
	body, err := c.doGet(ctx, reqURL)
	if err != nil {
		return "", fmt.Errorf("fetch diff: %w", err)
	}
	return string(body), nil
}

// GetPullRequestFiles fetches the list of files changed in a PR.
func (c *Client) GetPullRequestFiles(ctx context.Context, owner, repo string, number int) ([]ChangedFile, error) {
	reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/pulls/%d/files", c.baseURL, owner, repo, number)
	body, err := c.doGet(ctx, reqURL)
	if err != nil {
		return nil, fmt.Errorf("fetch PR files: %w", err)
	}
	var files []ChangedFile
	if err := json.Unmarshal(body, &files); err != nil {
		return nil, fmt.Errorf("parse PR files JSON: %w", err)
	}
	return files, nil
}

// GetCommitStatuses fetches CI statuses for a commit SHA.
func (c *Client) GetCommitStatuses(ctx context.Context, owner, repo, sha string) ([]CommitStatus, error) {
	reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/commits/%s/statuses", c.baseURL, owner, repo, sha)
	body, err := c.doGet(ctx, reqURL)
	if err != nil {
		return nil, fmt.Errorf("fetch commit statuses: %w", err)
	}
	var statuses []CommitStatus
	if err := json.Unmarshal(body, &statuses); err != nil {
		return nil, fmt.Errorf("parse statuses JSON: %w", err)
	}
	return statuses, nil
}

// GetFileContent fetches a file from the default branch of a repo.
func (c *Client) GetFileContent(ctx context.Context, owner, repo, filepath string) (string, error) {
	reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/raw/%s", c.baseURL, owner, repo, escapePath(filepath))
	body, err := c.doGet(ctx, reqURL)
	if err != nil {
		return "", fmt.Errorf("fetch file %s: %w", filepath, err)
	}
	return string(body), nil
}

// GetFileContentRef fetches a file from a specific ref (branch/tag/sha) in a repo.
func (c *Client) GetFileContentRef(ctx context.Context, owner, repo, filepath, ref string) (string, error) {
	reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/raw/%s?ref=%s", c.baseURL, owner, repo, escapePath(filepath), url.QueryEscape(ref))
	body, err := c.doGet(ctx, reqURL)
	if err != nil {
		return "", fmt.Errorf("fetch file %s@%s: %w", filepath, ref, err)
	}
	return string(body), nil
}

// PostReview submits a review to a PR and returns the created review.
// event should be "APPROVED" or "REQUEST_CHANGES".
// comments are optional inline comments attached to specific lines.
func (c *Client) PostReview(ctx context.Context, owner, repo string, number int, event, body string, comments []ReviewComment) (*Review, error) {
	reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/pulls/%d/reviews", c.baseURL, owner, repo, number)

	payload := struct {
		Body     string          `json:"body"`
		Event    string          `json:"event"`
		Comments []ReviewComment `json:"comments,omitempty"`
	}{
		Body:     body,
		Event:    event,
		Comments: comments,
	}

	data, err := json.Marshal(payload)
	if err != nil {
		return nil, fmt.Errorf("marshal review payload: %w", err)
	}

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, reqURL, bytes.NewReader(data))
	if err != nil {
		return nil, fmt.Errorf("create review request: %w", err)
	}
	req.Header.Set("Authorization", "token "+c.token)
	req.Header.Set("Content-Type", "application/json")

	resp, err := c.http.Do(req)
	if err != nil {
		return nil, fmt.Errorf("post review: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		respBody, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("post review failed (status %d): %s", resp.StatusCode, string(respBody))
	}

	respBody, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("read review response: %w", err)
	}
	var review Review
	if err := json.Unmarshal(respBody, &review); err != nil {
		return nil, fmt.Errorf("parse review response: %w", err)
	}
	return &review, nil
}

func (c *Client) doGet(ctx context.Context, reqURL string) ([]byte, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, reqURL, nil)
	if err != nil {
		return nil, err
	}
	req.Header.Set("Authorization", "token "+c.token)

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

	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		body, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("HTTP %d: %s", resp.StatusCode, string(body))
	}
	return io.ReadAll(resp.Body)
}

// escapePath escapes each segment of a relative file path for use in URLs.
// Slashes are preserved as path separators; other special characters are escaped.
// Input should be a relative path (no leading slash). Already-encoded segments
// will be double-encoded, which is the desired behavior for user-provided paths.
func escapePath(p string) string {
	parts := strings.Split(p, "/")
	for i, part := range parts {
		parts[i] = url.PathEscape(part)
	}
	return strings.Join(parts, "/")
}

// ContentEntry represents a file or directory entry from the contents API.
type ContentEntry struct {
	Name string `json:"name"`
	Path string `json:"path"`
	Type string `json:"type"` // "file" or "dir"
}

// ListContents lists files and directories at a given path in a repo.
// Pass an empty path to list the repository root.
func (c *Client) ListContents(ctx context.Context, owner, repo, path string) ([]ContentEntry, error) {
	var reqURL string
	if path == "" {
		reqURL = fmt.Sprintf("%s/api/v1/repos/%s/%s/contents", c.baseURL, owner, repo)
	} else {
		reqURL = fmt.Sprintf("%s/api/v1/repos/%s/%s/contents/%s", c.baseURL, owner, repo, escapePath(path))
	}
	body, err := c.doGet(ctx, reqURL)
	if err != nil {
		return nil, fmt.Errorf("list contents %s: %w", path, err)
	}
	var entries []ContentEntry
	if err := json.Unmarshal(body, &entries); err != nil {
		return nil, fmt.Errorf("parse contents JSON: %w", err)
	}
	return entries, nil
}

// GetAllFilesInPath recursively fetches all file contents under a path.
// If the path is a file, returns just that file's content.
// If the path is a directory, recursively fetches all files within it.
func (c *Client) GetAllFilesInPath(ctx context.Context, owner, repo, path string) (map[string]string, error) {
	results := make(map[string]string)

	// Try listing as directory first
	entries, err := c.ListContents(ctx, owner, repo, path)
	if err != nil {
		// Might be a file, try fetching directly
		content, fileErr := c.GetFileContent(ctx, owner, repo, path)
		if fileErr != nil {
			return nil, fmt.Errorf("path %q is neither a file nor directory: %w", path, err)
		}
		results[path] = content
		return results, nil
	}

	for _, entry := range entries {
		switch entry.Type {
		case "file":
			content, err := c.GetFileContent(ctx, owner, repo, entry.Path)
			if err != nil {
				log.Printf("Warning: could not fetch file %s: %v", entry.Path, err)
				continue
			}
			results[entry.Path] = content
		case "dir":
			subResults, err := c.GetAllFilesInPath(ctx, owner, repo, entry.Path)
			if err != nil {
				log.Printf("Warning: could not recurse into %s: %v", entry.Path, err)
				continue
			}
			for k, v := range subResults {
				results[k] = v
			}
		}
	}
	return results, nil
}

// Review represents a pull request review from the Gitea API.
type Review struct {
	ID   int64  `json:"id"`
	Body string `json:"body"`
	User struct {
		Login string `json:"login"`
	} `json:"user"`
	State string `json:"state"`
	Stale bool   `json:"stale"`
}

// ListReviews returns all reviews on a pull request.
// Paginates through all pages to ensure no reviews are missed.
func (c *Client) ListReviews(ctx context.Context, owner, repo string, number int) ([]Review, error) {
	const pageSize = 50
	var all []Review
	for page := 1; ; page++ {
		reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/pulls/%d/reviews?limit=%d&page=%d",
			c.baseURL,
			url.PathEscape(owner),
			url.PathEscape(repo),
			number,
			pageSize,
			page)
		body, err := c.doGet(ctx, reqURL)
		if err != nil {
			return nil, fmt.Errorf("list reviews (page %d): %w", page, err)
		}
		var batch []Review
		if err := json.Unmarshal(body, &batch); err != nil {
			return nil, fmt.Errorf("parse reviews (page %d): %w", page, err)
		}
		all = append(all, batch...)
		if len(batch) < pageSize {
			break
		}
	}
	return all, nil
}

// DeleteReview deletes a review by ID. The token must belong to the review author.
func (c *Client) DeleteReview(ctx context.Context, owner, repo string, number int, reviewID int64) error {
	reqURL := fmt.Sprintf("%s/api/v1/repos/%s/%s/pulls/%d/reviews/%d",
		c.baseURL,
		url.PathEscape(owner),
		url.PathEscape(repo),
		number,
		reviewID)

	req, err := http.NewRequestWithContext(ctx, http.MethodDelete, reqURL, nil)
	if err != nil {
		return fmt.Errorf("create delete request: %w", err)
	}
	req.Header.Set("Authorization", "token "+c.token)

	resp, err := c.http.Do(req)
	if err != nil {
		return fmt.Errorf("delete review: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		respBody, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("delete review failed (status %d): %s", resp.StatusCode, string(respBody))
	}
	return nil
}