package gitea

import (
	"fmt"
	"os"
	"strings"

	giteaSDK "code.gitea.io/sdk/gitea"
)

const prMarker = "<!-- stamp-release-pr -->"

// Client wraps the Gitea API.
type Client struct {
	client *giteaSDK.Client
	owner  string
	repo   string
}

const commentMarker = "<!-- stamp-pr-comment -->"

// NewClient creates a Gitea client from GITEA_TOKEN and GITEA_BASE_URL environment variables.
// The repoSlug must be in "owner/repo" format.
func NewClient(repoSlug string) (*Client, error) {
	token := os.Getenv("GITEA_TOKEN")
	if token == "" {
		return nil, fmt.Errorf("GITEA_TOKEN environment variable is not set")
	}
	baseURL := os.Getenv("GITEA_BASE_URL")
	if baseURL == "" {
		return nil, fmt.Errorf("GITEA_BASE_URL environment variable is not set")
	}

	parts := strings.SplitN(repoSlug, "/", 2)
	if len(parts) != 2 {
		return nil, fmt.Errorf("invalid repo slug %q: expected owner/repo", repoSlug)
	}

	client, err := giteaSDK.NewClient(baseURL, giteaSDK.SetToken(token))
	if err != nil {
		return nil, fmt.Errorf("creating Gitea client: %w", err)
	}
	return &Client{client: client, owner: parts[0], repo: parts[1]}, nil
}

// CreateRelease creates a Gitea release for the given tag.
func (c *Client) CreateRelease(tag, name, body string, draft, prerelease bool) (int64, error) {
	rel, _, err := c.client.CreateRelease(c.owner, c.repo, giteaSDK.CreateReleaseOption{
		TagName:      tag,
		Title:        name,
		Note:         body,
		IsDraft:      draft,
		IsPrerelease: prerelease,
	})
	if err != nil {
		return 0, fmt.Errorf("creating Gitea release %s: %w", tag, err)
	}
	return rel.ID, nil
}

// UploadAsset uploads a file to an existing Gitea release.
func (c *Client) UploadAsset(releaseID int64, filePath string) error {
	f, err := os.Open(filePath)
	if err != nil {
		return fmt.Errorf("opening %s: %w", filePath, err)
	}
	defer f.Close()

	name := strings.Split(filePath, "/")
	fileName := name[len(name)-1]

	_, _, err = c.client.CreateReleaseAttachment(c.owner, c.repo, releaseID, f, fileName)
	if err != nil {
		return fmt.Errorf("uploading %s to release %d: %w", fileName, releaseID, err)
	}
	return nil
}

// UpsertPR creates or updates a stamp release PR on the given base branch.
// It identifies the existing PR by scanning open PRs for the hidden marker in the body.
func (c *Client) UpsertPR(head, base, title, body string) (int64, string, error) {
	markedBody := prMarker + "\n" + body

	// Search open PRs for an existing stamp release PR (Gitea SDK does not support
	// filtering by head branch, so we filter client-side).
	prs, _, err := c.client.ListRepoPullRequests(c.owner, c.repo, giteaSDK.ListPullRequestsOptions{
		State: giteaSDK.StateOpen,
	})
	if err != nil {
		return 0, "", fmt.Errorf("listing pull requests: %w", err)
	}

	for _, pr := range prs {
		if pr.Head != nil && pr.Head.Name != head {
			continue
		}
		if strings.Contains(pr.Body, prMarker) {
			// Update existing PR.
			updated, _, err := c.client.EditPullRequest(c.owner, c.repo, pr.Index,
				giteaSDK.EditPullRequestOption{
					Title: title,
					Body:  &markedBody,
				})
			if err != nil {
				return 0, "", fmt.Errorf("updating pull request #%d: %w", pr.Index, err)
			}
			return updated.Index, updated.HTMLURL, nil
		}
	}

	// Create a new PR.
	pr, _, err := c.client.CreatePullRequest(c.owner, c.repo, giteaSDK.CreatePullRequestOption{
		Head:  head,
		Base:  base,
		Title: title,
		Body:  markedBody,
	})
	if err != nil {
		return 0, "", fmt.Errorf("creating pull request: %w", err)
	}
	return pr.Index, pr.HTMLURL, nil
}

// UpsertPRComment posts or updates a stamped PR comment.
func (c *Client) UpsertPRComment(prNumber int, body string) error {
	markedBody := commentMarker + "\n" + body

	comments, _, err := c.client.ListIssueComments(c.owner, c.repo, int64(prNumber),
		giteaSDK.ListIssueCommentOptions{})
	if err != nil {
		return fmt.Errorf("listing PR comments: %w", err)
	}

	for _, comment := range comments {
		if strings.Contains(comment.Body, commentMarker) {
			_, _, err = c.client.EditIssueComment(c.owner, c.repo, comment.ID,
				giteaSDK.EditIssueCommentOption{Body: markedBody})
			return err
		}
	}

	_, _, err = c.client.CreateIssueComment(c.owner, c.repo, int64(prNumber),
		giteaSDK.CreateIssueCommentOption{Body: markedBody})
	return err
}