package gitea

import (
	"context"
	"fmt"
	"log/slog"
	"strings"

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

// Adapter wraps a gitea.Client and satisfies the vcs.Client interface.
// It handles translation between GitHub-canonical diff positions and Gitea
// line numbers, and between canonical review event strings and Gitea-native values.
type Adapter struct {
	client *Client
}

// Compile-time interface conformance assertion.
var _ vcs.Client = (*Adapter)(nil)
var _ vcs.ReviewerSelfRequester = (*Adapter)(nil)

// NewAdapter creates a new Adapter wrapping the given gitea Client.
func NewAdapter(client *Client) *Adapter {
	return &Adapter{client: client}
}

// Underlying returns the wrapped gitea.Client for Gitea-specific operations
// that have no vcs.Client equivalent (resolve comment, timeline, supersede flow).
func (a *Adapter) Underlying() *Client {
	return a.client
}

// --- PRReader ---

// GetPullRequest maps gitea.PullRequest to vcs.PullRequest.
func (a *Adapter) GetPullRequest(ctx context.Context, owner, repo string, number int) (*vcs.PullRequest, error) {
	pr, err := a.client.GetPullRequest(ctx, owner, repo, number)
	if err != nil {
		return nil, fmt.Errorf("get pull request: %w", err)
	}
	return &vcs.PullRequest{
		Number: number,
		Title:  pr.Title,
		Body:   pr.Body,
		Head: vcs.HeadRef{
			SHA: pr.Head.Sha,
			Ref: pr.Head.Ref,
		},
		Base: vcs.BaseRef{
			Ref: pr.Base.Ref,
		},
	}, nil
}

// GetPullRequestDiff is a pass-through to the underlying client.
func (a *Adapter) GetPullRequestDiff(ctx context.Context, owner, repo string, number int) (string, error) {
	return a.client.GetPullRequestDiff(ctx, owner, repo, number)
}

// GetPullRequestFiles maps []gitea.ChangedFile to []vcs.ChangedFile.
// Patch field is omitted (zero-value) since Gitea's /pulls/{n}/files does not return patch text.
func (a *Adapter) GetPullRequestFiles(ctx context.Context, owner, repo string, number int) ([]vcs.ChangedFile, error) {
	files, err := a.client.GetPullRequestFiles(ctx, owner, repo, number)
	if err != nil {
		return nil, err
	}
	result := make([]vcs.ChangedFile, len(files))
	for i, f := range files {
		result[i] = vcs.ChangedFile{
			Filename: f.Filename,
			Status:   f.Status,
		}
	}
	return result, nil
}

// GetFileContentAtRef is a pass-through to the underlying client.
func (a *Adapter) GetFileContentAtRef(ctx context.Context, owner, repo, path, ref string) (string, error) {
	return a.client.GetFileContentAtRef(ctx, owner, repo, path, ref)
}

// GetCommitStatuses maps []gitea.CommitStatus to []vcs.CommitStatus.
func (a *Adapter) GetCommitStatuses(ctx context.Context, owner, repo, sha string) ([]vcs.CommitStatus, error) {
	statuses, err := a.client.GetCommitStatuses(ctx, owner, repo, sha)
	if err != nil {
		return nil, err
	}
	result := make([]vcs.CommitStatus, len(statuses))
	for i, s := range statuses {
		result[i] = vcs.CommitStatus{
			Status:      s.Status,
			Context:     s.Context,
			Description: s.Description,
			TargetURL:   s.TargetURL,
		}
	}
	return result, nil
}

// --- FileReader ---

// GetFileContent delegates to the underlying client, routing to the ref-aware
// variant when ref is non-empty.
func (a *Adapter) GetFileContent(ctx context.Context, owner, repo, path, ref string) (string, error) {
	if ref != "" {
		return a.client.GetFileContentRef(ctx, owner, repo, path, ref)
	}
	return a.client.GetFileContent(ctx, owner, repo, path)
}

// ListContents maps []gitea.ContentEntry to []vcs.ContentEntry.
func (a *Adapter) ListContents(ctx context.Context, owner, repo, path string) ([]vcs.ContentEntry, error) {
	entries, err := a.client.ListContents(ctx, owner, repo, path)
	if err != nil {
		return nil, err
	}
	result := make([]vcs.ContentEntry, len(entries))
	for i, e := range entries {
		result[i] = vcs.ContentEntry{
			Name: e.Name,
			Path: e.Path,
			Type: e.Type,
		}
	}
	return result, nil
}

// --- Reviewer ---

// translateEvent translates a vcs.ReviewEvent (GitHub-canonical) to a Gitea-native event string.
func translateEvent(event vcs.ReviewEvent) string {
	switch event {
	case vcs.ReviewEventApprove:
		return "APPROVED"
	case vcs.ReviewEventRequestChanges:
		return "REQUEST_CHANGES"
	case vcs.ReviewEventComment:
		return "COMMENT"
	default:
		// Unknown events pass through as-is. This is intentional: new event types
		// added to vcs.ReviewEvent will still be forwarded without a code change here,
		// and Gitea will reject truly invalid values with a clear API error.
		return string(event)
	}
}

// PostReview translates vcs.ReviewRequest to the Gitea-native format.
// It fetches the PR diff, builds a position-to-line map, and translates each
// ReviewComment.Position (GitHub diff-position) to a Gitea new_position (line number).
func (a *Adapter) PostReview(ctx context.Context, owner, repo string, number int, req vcs.ReviewRequest) (*vcs.Review, error) {
	event := translateEvent(req.Event)

	var giteaComments []ReviewComment
	if len(req.Comments) > 0 {
		// Fetch diff to build position → line number map.
		// The diff is fetched unconditionally when comments exist. This adds latency
		// for reviews with inline comments but keeps the implementation simple — caching
		// the diff across calls would add complexity for minimal gain since PostReview
		// is called at most once per review cycle.
		diff, err := a.client.GetPullRequestDiff(ctx, owner, repo, number)
		if err != nil {
			return nil, fmt.Errorf("fetch diff for position translation: %w", err)
		}

		posMap := BuildPositionToLineMap(diff)

		for _, c := range req.Comments {
			lineNum, err := posMap.Translate(c.Path, c.Position)
			if err != nil {
				return nil, fmt.Errorf("translate position %d in %s: %w", c.Position, c.Path, err)
			}
			// Per-comment CommitID is not forwarded to Gitea inline comments:
			// Gitea's CreatePullReview API has no per-comment commit_id field.
			// The review-level commit anchor is set via req.CommitID instead.
			giteaComments = append(giteaComments, ReviewComment{
				Path:        c.Path,
				NewPosition: int64(lineNum),
				Body:        c.Body,
			})
		}
	}

	review, err := a.client.PostReview(ctx, owner, repo, number, event, req.Body, req.CommitID, giteaComments)
	if err != nil {
		return nil, fmt.Errorf("post review: %w", err)
	}

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

// ListReviews maps []gitea.Review to []vcs.Review.
func (a *Adapter) ListReviews(ctx context.Context, owner, repo string, number int) ([]vcs.Review, error) {
	reviews, err := a.client.ListReviews(ctx, owner, repo, number)
	if err != nil {
		return nil, err
	}
	result := make([]vcs.Review, len(reviews))
	for i, r := range reviews {
		result[i] = vcs.Review{
			ID:       r.ID,
			Body:     r.Body,
			User:     vcs.UserInfo{Login: r.User.Login},
			State:    r.State,
			Stale:    r.Stale,
			CommitID: r.CommitID,
		}
	}
	return result, nil
}

// DeleteReview is a pass-through to the underlying client.
func (a *Adapter) DeleteReview(ctx context.Context, owner, repo string, number int, reviewID int64) error {
	return a.client.DeleteReview(ctx, owner, repo, number, reviewID)
}

// DismissReview deletes the review. Gitea supports full deletion of any review state.
// The message parameter is intentionally unused — Gitea deletion has no dismissal message.
func (a *Adapter) DismissReview(ctx context.Context, owner, repo string, number int, reviewID int64, message string) error {
	return a.client.DeleteReview(ctx, owner, repo, number, reviewID)
}

// --- Identity ---

// GetAuthenticatedUser is a pass-through to the underlying client.
func (a *Adapter) GetAuthenticatedUser(ctx context.Context) (string, error) {
	return a.client.GetAuthenticatedUser(ctx)
}

// RequestReviewerSelf adds the given user as a requested reviewer on a pull request.
// This implements vcs.ReviewerSelfRequester for the Gitea adapter.
func (a *Adapter) RequestReviewerSelf(ctx context.Context, owner, repo string, number int, user string) error {
	return a.client.RequestReviewer(ctx, owner, repo, number, user)
}

// Compile-time interface conformance assertion for ReviewSuperseder.
var _ vcs.ReviewSuperseder = (*Adapter)(nil)

// SupersedeReviews marks prior reviews as superseded by editing their body with a
// link to the new review and resolving their inline comments. This is Gitea-specific
// behavior that has no GitHub equivalent (GitHub uses DismissReview instead).
//
// baseURL is the Gitea instance URL used to construct review permalink URLs.
// sentinel is the HTML comment sentinel that identifies reviews belonging to this reviewer.
func (a *Adapter) SupersedeReviews(ctx context.Context, owner, repo string, prNumber int, oldReviews []vcs.Review, newReviewID int64, baseURL, sentinel string) error {
	// Validate baseURL scheme before embedding in Markdown link (defense-in-depth).
	if !strings.HasPrefix(baseURL, "http://") && !strings.HasPrefix(baseURL, "https://") {
		return fmt.Errorf("SupersedeReviews: baseURL must have http or https scheme, got %q", baseURL)
	}

	underlying := a.client

	newReviewURL := fmt.Sprintf("%s/%s/%s/pulls/%d#pullrequestreview-%d",
		strings.TrimRight(baseURL, "/"), owner, repo, prNumber, newReviewID)

	for _, oldReview := range oldReviews {
		cid, err := underlying.GetTimelineReviewCommentIDForReview(ctx, owner, repo, prNumber, oldReview.ID)
		if err != nil {
			slog.Warn("could not find comment ID for old review", "review_id", oldReview.ID, "error", err)
			continue
		}
		supersededBody := buildSupersededBody(oldReview.Body, oldReview.CommitID, newReviewURL, sentinel)
		if err := underlying.EditComment(ctx, owner, repo, cid, supersededBody); err != nil {
			slog.Warn("could not mark old review as superseded", "review_id", oldReview.ID, "error", err)
			continue
		}

		// Resolve old review's inline comments
		oldComments, err := underlying.ListReviewComments(ctx, owner, repo, prNumber, oldReview.ID)
		if err != nil {
			slog.Warn("could not list old review comments for resolution", "review_id", oldReview.ID, "error", err)
			continue
		}
		for _, c := range oldComments {
			if c.ID == 0 {
				continue
			}
			if err := underlying.ResolveComment(ctx, owner, repo, c.ID); err != nil {
				slog.Debug("could not resolve inline comment", "comment_id", c.ID, "error", err)
			}
		}
	}
	return nil
}

// buildSupersededBody creates the body for a superseded review: struck-through banner
// with collapsed original content and the commit it was evaluated against.
func buildSupersededBody(originalBody, commitSHA, newReviewURL, sentinel string) string {
	shortSHA := commitSHA
	if len(shortSHA) > 8 {
		shortSHA = shortSHA[:8]
	}
	var sb strings.Builder
	sb.WriteString("~~Original review~~\n\n")
	sb.WriteString("**Superseded** \u2014 [see current review](")
	sb.WriteString(newReviewURL)
	sb.WriteString(") for up-to-date findings.\n\n")
	if shortSHA != "" {
		sb.WriteString("<details><summary>Previous findings (commit ")
		sb.WriteString(shortSHA)
		sb.WriteString(")</summary>\n\n")
	} else {
		sb.WriteString("<details><summary>Previous findings</summary>\n\n")
	}
	sb.WriteString(originalBody)
	sb.WriteString("\n\n</details>\n\n")
	sb.WriteString(sentinel)
	return sb.String()
}