package gitea

import (
	"bytes"
	"embed"
	"strings"
	"text/template"

	"code.gitea.io/sdk/gitea"
	"github.com/golangci/golangci-lint/pkg/report"
	"github.com/golangci/golangci-lint/pkg/result"
	"golang.org/x/exp/slog"

	"code.icb4dc0.de/prskr/nitter/nitters"
)

const summaryFooter = "\n\n(Created by nitter)"

var (
	_ nitters.Nitter = (*prNitter)(nil)

	//go:embed templates/*
	templatesFS embed.FS
	templates   *template.Template
)

func init() {
	if tmpl, err := template.New("issue_templates").ParseFS(templatesFS, "templates/*.tmpl.md"); err != nil {
		panic(err)
	} else {
		templates = tmpl
	}
}

func NewPRNitter(logger *slog.Logger, cli Client, cfg *GiteaPRConfig) *prNitter {

	if logger == nil {
		logger = slog.Default()
	}

	return &prNitter{
		Client: cli,
		logger: logger,
		cfg:    cfg,
	}
}

type prNitter struct {
	Client
	logger *slog.Logger
	cfg    *GiteaPRConfig
}

func (p prNitter) Report(report *report.Data, issues []result.Issue) error {
	me, _, err := p.GetMyUserInfo()
	if err != nil {
		return err
	}

	slog.Debug("Running as", slog.String("name", me.UserName))

	pr, _, err := p.GetPullRequest(p.cfg.Namespace, p.cfg.Repo, p.cfg.PRIndex)
	if err != nil {
		slog.Error("Failed to get PR details", err, slog.Int64("index", p.cfg.PRIndex))
		return err
	}

	review, err := p.preparePullReview(report, issues, me, pr)
	if err != nil {
		return err
	}

	if err := p.cleanOutdatedReviews(me); err != nil {
		return err
	}

	if _, _, err := p.CreatePullReview(p.cfg.Namespace, p.cfg.Repo, p.cfg.PRIndex, *review); err != nil {
		slog.Error("Failed to submit new PR review", err)
		return err
	}

	return nil
}

func (p prNitter) preparePullReview(
	report *report.Data,
	issues []result.Issue,
	me *gitea.User,
	pr *gitea.PullRequest,
) (*gitea.CreatePullReviewOptions, error) {
	templateBuf := bytes.Buffer{}
	summaryData := map[string]any{
		"Report": report,
		"Issues": issues,
	}

	if err := templates.ExecuteTemplate(&templateBuf, "issue_summary.tmpl.md", summaryData); err != nil {
		return nil, err
	}

	_, _ = templateBuf.WriteString(summaryFooter)

	pullReviewOptions := &gitea.CreatePullReviewOptions{
		State:    p.cfg.ReviewState,
		Body:     templateBuf.String(),
		Comments: make([]gitea.CreatePullReviewComment, 0, len(issues)),
	}

	if len(issues) == 0 {
		if me.ID != pr.Poster.ID {
			pullReviewOptions.State = gitea.ReviewStateApproved
		} else {
			slog.Warn(
				"Cannot approve PR if token is issued by the same user - fallback to comment state",
				slog.String("nitter_user", me.UserName),
				slog.String("pr_poster", pr.Poster.UserName),
			)

			pullReviewOptions.State = gitea.ReviewStateComment
		}
	} else {
		templateBuf.Reset()
		for i := range issues {
			templateData := map[string]any{
				"Issue": issues[i],
			}
			if err := templates.ExecuteTemplate(&templateBuf, "issue_comment.tmpl.md", templateData); err != nil {
				return nil, err
			}

			pullReviewOptions.Comments = append(pullReviewOptions.Comments, gitea.CreatePullReviewComment{
				Path:       issues[i].Pos.Filename,
				Body:       templateBuf.String(),
				NewLineNum: int64(issues[i].Pos.Line),
			})

			templateBuf.Reset()
		}
	}

	return pullReviewOptions, nil
}

func (p prNitter) cleanOutdatedReviews(me *gitea.User) error {
	reviews, _, err := p.ListPullReviews(p.cfg.Namespace, p.cfg.Repo, p.cfg.PRIndex, gitea.ListPullReviewsOptions{})
	if err != nil {
		return err
	}

	for i := range reviews {
		review := reviews[i]
		if review.Reviewer.ID == me.ID && strings.HasSuffix(review.Body, summaryFooter) {
			if _, err = p.DeletePullReview(p.cfg.Namespace, p.cfg.Repo, p.cfg.PRIndex, review.ID); err != nil {
				slog.Error("Failed to delete existing review", err, slog.Int64("reviewId", review.ID))
				return err
			}
		}
	}

	return nil
}