package github

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"net/url"

	"gitea.weiker.me/rodin/review-bot/vcs"
)

const (
	// reviewsPerPage is the number of reviews to fetch per API page.
	reviewsPerPage = 100
	// maxReviewPages is the maximum number of pages to paginate through
	// when listing reviews. Acts as a safeguard against infinite pagination.
	maxReviewPages = 100
)

// reviewResponse is the GitHub API response for a pull request review.
type reviewResponse struct {
	ID   int64  `json:"id"`
	Body string `json:"body"`
	User struct {
		Login string `json:"login"`
	} `json:"user"`
	State    string `json:"state"`
	CommitID string `json:"commit_id"`
}

// reviewCreateRequest is the GitHub API request body for creating a pull request review.
type reviewCreateRequest struct {
	Body     string                `json:"body"`
	Event    string                `json:"event"`
	Comments []reviewCommentCreate `json:"comments,omitempty"`
	CommitID string                `json:"commit_id,omitempty"`
}

// reviewCommentCreate is a single inline comment in a review creation request.
type reviewCommentCreate struct {
	Path     string `json:"path"`
	Position int    `json:"position"`
	Body     string `json:"body"`
}

// dismissReviewRequest is the GitHub API request body for dismissing a review.
type dismissReviewRequest struct {
	Message string `json:"message"`
}

// userResponse is the GitHub API response for the authenticated user.
type userResponse struct {
	Login string `json:"login"`
}

// translateReviewEvent converts a vcs.ReviewEvent to the GitHub API event string.
func translateReviewEvent(event vcs.ReviewEvent) string {
	switch event {
	case vcs.ReviewEventApprove:
		return "APPROVE"
	case vcs.ReviewEventRequestChanges:
		return "REQUEST_CHANGES"
	default:
		return "COMMENT"
	}
}

// PostReview creates a new review on a pull request.
func (c *Client) PostReview(ctx context.Context, owner, repo string, number int, req vcs.ReviewRequest) (*vcs.Review, error) {
	reqURL := fmt.Sprintf("%s/repos/%s/%s/pulls/%d/reviews",
		c.baseURL, url.PathEscape(owner), url.PathEscape(repo), number)

	payload := reviewCreateRequest{
		Body:  req.Body,
		Event: translateReviewEvent(req.Event),
	}

	for _, comment := range req.Comments {
		rc := reviewCommentCreate{
			Path:     comment.Path,
			Position: comment.Position,
			Body:     comment.Body,
		}
		payload.Comments = append(payload.Comments, rc)
		// Use CommitID from the first comment that has one.
		// All comments in a single review are expected to reference the same commit.
		if payload.CommitID == "" && comment.CommitID != "" {
			payload.CommitID = comment.CommitID
		}
	}

	body, err := c.doJSONRequest(ctx, http.MethodPost, reqURL, payload)
	if err != nil {
		return nil, fmt.Errorf("post review: %w", err)
	}

	var resp reviewResponse
	if err := json.Unmarshal(body, &resp); err != nil {
		return nil, fmt.Errorf("parse review response: %w", err)
	}

	return &vcs.Review{
		ID:       resp.ID,
		Body:     resp.Body,
		User:     vcs.UserInfo{Login: resp.User.Login},
		State:    resp.State,
		CommitID: resp.CommitID,
	}, nil
}

// ListReviews lists all reviews on a pull request.
func (c *Client) ListReviews(ctx context.Context, owner, repo string, number int) ([]vcs.Review, error) {
	var allReviews []vcs.Review

	for page := 1; page <= maxReviewPages; page++ {
		reqURL := fmt.Sprintf("%s/repos/%s/%s/pulls/%d/reviews?per_page=%d&page=%d",
			c.baseURL, url.PathEscape(owner), url.PathEscape(repo), number, reviewsPerPage, page)
		body, err := c.doGet(ctx, reqURL)
		if err != nil {
			return nil, fmt.Errorf("list reviews page %d: %w", page, err)
		}
		var reviews []reviewResponse
		if err := json.Unmarshal(body, &reviews); err != nil {
			return nil, fmt.Errorf("parse reviews JSON: %w", err)
		}
		if len(reviews) == 0 {
			break
		}
		for _, r := range reviews {
			allReviews = append(allReviews, vcs.Review{
				ID:       r.ID,
				Body:     r.Body,
				User:     vcs.UserInfo{Login: r.User.Login},
				State:    r.State,
				CommitID: r.CommitID,
			})
		}
		if len(reviews) < reviewsPerPage {
			break
		}
	}

	return allReviews, nil
}

// DeleteReview permanently deletes a review from a pull request.
// Use DismissReview instead when the review should remain visible but marked as dismissed
// (e.g., superseding an outdated review while preserving history).
func (c *Client) DeleteReview(ctx context.Context, owner, repo string, number int, reviewID int64) error {
	reqURL := fmt.Sprintf("%s/repos/%s/%s/pulls/%d/reviews/%d",
		c.baseURL, url.PathEscape(owner), url.PathEscape(repo), number, reviewID)
	_, err := c.doRequest(ctx, http.MethodDelete, reqURL, "")
	if err != nil {
		return fmt.Errorf("delete review: %w", err)
	}
	return nil
}

// DismissReview dismisses a review on a pull request with a message.
func (c *Client) DismissReview(ctx context.Context, owner, repo string, number int, reviewID int64, message string) error {
	reqURL := fmt.Sprintf("%s/repos/%s/%s/pulls/%d/reviews/%d/dismissals",
		c.baseURL, url.PathEscape(owner), url.PathEscape(repo), number, reviewID)

	payload := dismissReviewRequest{
		Message: message,
	}

	_, err := c.doJSONRequest(ctx, http.MethodPut, reqURL, payload)
	if err != nil {
		return fmt.Errorf("dismiss review: %w", err)
	}
	return nil
}

// GetAuthenticatedUser returns the login name of the authenticated user.
func (c *Client) GetAuthenticatedUser(ctx context.Context) (string, error) {
	reqURL := fmt.Sprintf("%s/user", c.baseURL)
	body, err := c.doGet(ctx, reqURL)
	if err != nil {
		return "", fmt.Errorf("get authenticated user: %w", err)
	}
	var resp userResponse
	if err := json.Unmarshal(body, &resp); err != nil {
		return "", fmt.Errorf("parse user response: %w", err)
	}
	return resp.Login, nil
}