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"`
}

// GetPullRequest fetches PR metadata.
func (c *Client) GetPullRequest(ctx context.Context, owner, repo string, number int) (*PullRequest, error) {
	url := fmt.Sprintf("%s/api/v1/repos/%s/%s/pulls/%d", c.baseURL, owner, repo, number)
	body, err := c.doGet(ctx, url)
	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) {
	url := fmt.Sprintf("%s/api/v1/repos/%s/%s/pulls/%d.diff", c.baseURL, owner, repo, number)
	body, err := c.doGet(ctx, url)
	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) {
	url := fmt.Sprintf("%s/api/v1/repos/%s/%s/pulls/%d/files", c.baseURL, owner, repo, number)
	body, err := c.doGet(ctx, url)
	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) {
	url := fmt.Sprintf("%s/api/v1/repos/%s/%s/commits/%s/statuses", c.baseURL, owner, repo, sha)
	body, err := c.doGet(ctx, url)
	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) {
	url := fmt.Sprintf("%s/api/v1/repos/%s/%s/raw/%s", c.baseURL, owner, repo, filepath)
	body, err := c.doGet(ctx, url)
	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, 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.
// event should be "APPROVED" or "REQUEST_CHANGES".
func (c *Client) PostReview(ctx context.Context, owner, repo string, number int, event, body string) error {
	url := 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"`
	}{
		Body:  body,
		Event: event,
	}

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

	req, err := http.NewRequestWithContext(ctx, "POST", url, bytes.NewReader(data))
	if err != nil {
		return 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 fmt.Errorf("post review: %w", err)
	}
	defer resp.Body.Close()

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

func (c *Client) doGet(ctx context.Context, url string) ([]byte, error) {
	req, err := http.NewRequestWithContext(ctx, "GET", url, 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)
}

// 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.
func (c *Client) ListContents(ctx context.Context, owner, repo, path string) ([]ContentEntry, error) {
	url := fmt.Sprintf("%s/api/v1/repos/%s/%s/contents/%s", c.baseURL, owner, repo, path)
	body, err := c.doGet(ctx, url)
	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
}