package github

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

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

// ErrCannotDeleteSubmittedReview is returned when DeleteReview is called on
// a review that has already been submitted (APPROVED, REQUEST_CHANGES, COMMENT).
// GitHub only allows deletion of PENDING reviews. Callers that need to replace
// a submitted review should use DismissReview instead.
var ErrCannotDeleteSubmittedReview = errors.New("cannot delete submitted review: use DismissReview instead")

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

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

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

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

// translateGitHubReviewState translates a GitHub API review state to the
// canonical vcs.Review.State value.
func translateGitHubReviewState(state string) string {
	switch state {
	case "APPROVED":
		return "APPROVED"
	case "CHANGES_REQUESTED":
		return "REQUEST_CHANGES"
	case "COMMENTED":
		return "COMMENT"
	case "DISMISSED":
		return "DISMISSED"
	default:
		return state
	}
}

// PostReview submits a review on a pull request.
// The ReviewRequest.Event values (APPROVE, REQUEST_CHANGES, COMMENT) are sent
// directly — they match GitHub's canonical event strings.
// ReviewComment.Position maps directly to the GitHub API position field.
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 := postReviewRequest{
		Body:  req.Body,
		Event: string(req.Event),
	}

	// Populate CommitID from the first comment if available.
	// All comments in a single review share the same commit_id.
	for _, comment := range req.Comments {
		if comment.CommitID != "" {
			payload.CommitID = comment.CommitID
			break
		}
	}

	for _, comment := range req.Comments {
		payload.Comments = append(payload.Comments, reviewCommentEntry{
			Path:     comment.Path,
			Position: comment.Position,
			Body:     comment.Body,
		})
	}

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

	body, err := c.doRequestWithBody(ctx, "POST", reqURL, data)
	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:    translateGitHubReviewState(resp.State),
		CommitID: resp.CommitID,
	}, nil
}

// ListReviews retrieves all reviews for a pull request.
// GitHub review states are translated to canonical vcs values.
func (c *Client) ListReviews(ctx context.Context, owner, repo string, number int) ([]vcs.Review, error) {
	reqURL := fmt.Sprintf("%s/repos/%s/%s/pulls/%d/reviews",
		c.baseURL, url.PathEscape(owner), url.PathEscape(repo), number)

	body, err := c.doGet(ctx, reqURL)
	if err != nil {
		return nil, fmt.Errorf("list reviews: %w", err)
	}

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

	reviews := make([]vcs.Review, len(responses))
	for i, r := range responses {
		reviews[i] = vcs.Review{
			ID:       r.ID,
			Body:     r.Body,
			User:     vcs.UserInfo{Login: r.User.Login},
			State:    translateGitHubReviewState(r.State),
			CommitID: r.CommitID,
		}
	}
	return reviews, nil
}

// DeleteReview deletes a pull request review.
// Only PENDING reviews can be deleted; attempting to delete a submitted review
// (APPROVED, CHANGES_REQUESTED, COMMENTED) returns ErrCannotDeleteSubmittedReview.
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.doRequestWithBody(ctx, "DELETE", reqURL, nil)
	if err != nil {
		var apiErr *APIError
		if errors.As(err, &apiErr) && apiErr.StatusCode == 422 {
			return ErrCannotDeleteSubmittedReview
		}
		return fmt.Errorf("delete review: %w", err)
	}
	return nil
}

// DismissReview dismisses a submitted review on a pull request.
// This is the correct way to "remove" a submitted review (APPROVED, REQUEST_CHANGES).
// GitHub does not allow deleting submitted reviews — they must be dismissed.
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,
		Event:   "DISMISS",
	}

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

	_, err = c.doRequestWithBody(ctx, "PUT", reqURL, data)
	if err != nil {
		return fmt.Errorf("dismiss review: %w", err)
	}
	return nil
}