// Package gitea provides a minimal Gitea API client for fetching PR diffs
// and posting review comments.
package gitea

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"time"
)

const maxDiffBytes = 100 * 1024 // 100 KB — well within deepseek-coder's context

// Client is a minimal Gitea API client.
type Client struct {
	BaseURL string
	Token   string
	http    *http.Client
}

// New creates a new Gitea client.
func New(baseURL, token string) *Client {
	return &Client{
		BaseURL: baseURL,
		Token:   token,
		http:    &http.Client{Timeout: 30 * time.Second},
	}
}

func (c *Client) newRequest(method, url string, body []byte) (*http.Request, error) {
	var req *http.Request
	var err error
	if body != nil {
		req, err = http.NewRequest(method, url, bytes.NewReader(body))
	} else {
		req, err = http.NewRequest(method, url, nil)
	}
	if err != nil {
		return nil, err
	}
	req.Header.Set("Authorization", "token "+c.Token)
	if body != nil {
		req.Header.Set("Content-Type", "application/json")
	}
	return req, nil
}

// FetchDiff returns the unified diff for a pull request.
// It fetches the raw .diff endpoint and caps the result at maxDiffBytes.
func (c *Client) FetchDiff(owner, repo string, number int) (string, error) {
	url := fmt.Sprintf("%s/%s/%s/pulls/%d.diff", c.BaseURL, owner, repo, number)
	req, err := c.newRequest("GET", url, nil)
	if err != nil {
		return "", err
	}
	resp, err := c.http.Do(req)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		return "", fmt.Errorf("gitea: fetch diff %s/%s#%d: %s", owner, repo, number, resp.Status)
	}
	b, err := io.ReadAll(io.LimitReader(resp.Body, maxDiffBytes))
	if err != nil {
		return "", err
	}
	return string(b), nil
}

// PostComment posts a comment on a pull request.
// In Gitea, pull request comments are posted via the issues API using the PR number.
func (c *Client) PostComment(owner, repo string, number int, body string) error {
	url := fmt.Sprintf("%s/api/v1/repos/%s/%s/issues/%d/comments", c.BaseURL, owner, repo, number)
	payload, _ := json.Marshal(map[string]string{"body": body})
	req, err := c.newRequest("POST", url, payload)
	if err != nil {
		return err
	}
	resp, err := c.http.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()
	if resp.StatusCode >= 300 {
		return fmt.Errorf("gitea: post comment %s/%s#%d: %s", owner, repo, number, resp.Status)
	}
	return nil
}