package github

import (
	"context"
	"fmt"
	"os"
	"strings"

	gh "github.com/google/go-github/v70/github"
)

// Client wraps the GitHub REST API.
type Client struct {
	client *gh.Client
	owner  string
	repo   string
}

// NewClient creates a GitHub client from the GITHUB_TOKEN environment variable.
// The repoSlug must be in "owner/repo" format.
func NewClient(repoSlug string) (*Client, error) {
	token := os.Getenv("GITHUB_TOKEN")
	if token == "" {
		return nil, fmt.Errorf("GITHUB_TOKEN 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)
	}
	return &Client{
		client: gh.NewClient(nil).WithAuthToken(token),
		owner:  parts[0],
		repo:   parts[1],
	}, nil
}

// CreateRelease creates a GitHub release for the given tag.
func (c *Client) CreateRelease(ctx context.Context, tag, name, body string, draft, prerelease bool) (int64, error) {
	rel, _, err := c.client.Repositories.CreateRelease(ctx, c.owner, c.repo, &gh.RepositoryRelease{
		TagName:    gh.Ptr(tag),
		Name:       gh.Ptr(name),
		Body:       gh.Ptr(body),
		Draft:      gh.Ptr(draft),
		Prerelease: gh.Ptr(prerelease),
	})
	if err != nil {
		return 0, fmt.Errorf("creating GitHub release %s: %w", tag, err)
	}
	return rel.GetID(), nil
}

// UploadAsset uploads a file to an existing release.
func (c *Client) UploadAsset(ctx context.Context, 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.Repositories.UploadReleaseAsset(ctx, c.owner, c.repo, releaseID,
		&gh.UploadOptions{Name: fileName}, f)
	if err != nil {
		return fmt.Errorf("uploading %s to release %d: %w", fileName, releaseID, err)
	}
	return nil
}

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

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

	// List existing comments to find ours.
	comments, _, err := c.client.Issues.ListComments(ctx, c.owner, c.repo, prNumber, nil)
	if err != nil {
		return fmt.Errorf("listing PR comments: %w", err)
	}

	for _, comment := range comments {
		if strings.Contains(comment.GetBody(), commentMarker) {
			// Update existing comment.
			_, _, err = c.client.Issues.EditComment(ctx, c.owner, c.repo, comment.GetID(),
				&gh.IssueComment{Body: gh.Ptr(markedBody)})
			return err
		}
	}

	// Create new comment.
	_, _, err = c.client.Issues.CreateComment(ctx, c.owner, c.repo, prNumber,
		&gh.IssueComment{Body: gh.Ptr(markedBody)})
	return err
}