"use client";

import { useState } from "react";
import { useQuery } from "@tanstack/react-query";
import {
  CheckCircle2,
  CircleDashed,
  GitMerge,
  GitPullRequest,
  GitPullRequestArrow,
  GitPullRequestClosed,
  GitPullRequestDraft,
  TriangleAlert,
  XCircle,
} from "lucide-react";
import {
  issuePullRequestsOptions,
  derivePullRequestStatusKind,
  derivePullRequestProgressSegments,
  shouldShowPullRequestStats,
  type PullRequestStatusKind,
  type PullRequestProgressSegment,
} from "@multica/core/github";
import type {
  GitHubPullRequest,
  GitHubPullRequestChecksConclusion,
  GitHubPullRequestState,
} from "@multica/core/types";
import { cn } from "@multica/ui/lib/utils";
import { useT } from "../../i18n";

type IssuesT = ReturnType<typeof useT<"issues">>["t"];

// Keep the existing sidebar density: show the first 3 PR rows inline, then
// collapse the rest once the section reaches 4 rows.
const PR_LIMIT_BEFORE_COLLAPSE = 4;

const STATE_ICON: Record<
  GitHubPullRequestState,
  { icon: React.ComponentType<{ className?: string }>; className: string }
> = {
  open: { icon: GitPullRequestArrow, className: "text-emerald-600 dark:text-emerald-400" },
  draft: { icon: GitPullRequestDraft, className: "text-muted-foreground" },
  merged: { icon: GitMerge, className: "text-violet-600 dark:text-violet-400" },
  closed: { icon: GitPullRequestClosed, className: "text-rose-600 dark:text-rose-400" },
};

const CHECKS_ICON: Record<
  GitHubPullRequestChecksConclusion,
  { icon: React.ComponentType<{ className?: string }>; className: string }
> = {
  passed: { icon: CheckCircle2, className: "text-emerald-600 dark:text-emerald-400" },
  failed: { icon: XCircle, className: "text-rose-600 dark:text-rose-400" },
  pending: { icon: CircleDashed, className: "text-amber-600 dark:text-amber-400" },
};

export function PullRequestList({ issueId }: { issueId: string }) {
  const { t } = useT("issues");
  const [expanded, setExpanded] = useState(false);
  const { data, isLoading } = useQuery(issuePullRequestsOptions(issueId));
  const prs = data?.pull_requests ?? [];

  if (isLoading) {
    return <p className="text-xs text-muted-foreground px-2">{t(($) => $.detail.pull_requests_loading)}</p>;
  }
  if (prs.length === 0) {
    return (
      <p className="text-xs text-muted-foreground px-2">
        {t(($) => $.detail.pull_requests_empty)}
      </p>
    );
  }

  // Render rule:
  //   - <  PR_LIMIT_BEFORE_COLLAPSE: every PR row is visible.
  //   - >= PR_LIMIT_BEFORE_COLLAPSE: first (LIMIT - 1) rows are visible and
  //     the remainder sits behind a toggle.
  const useCollapse = prs.length >= PR_LIMIT_BEFORE_COLLAPSE;
  const expandedHead = useCollapse ? prs.slice(0, PR_LIMIT_BEFORE_COLLAPSE - 1) : prs;
  const collapsedTail = useCollapse ? prs.slice(PR_LIMIT_BEFORE_COLLAPSE - 1) : [];

  return (
    <div className="space-y-1">
      {expandedHead.map((pr) => (
        <PullRequestRow key={pr.id} pr={pr} />
      ))}
      {useCollapse ? (
        <div className="space-y-1">
          {expanded
            ? collapsedTail.map((pr) => <PullRequestRow key={pr.id} pr={pr} />)
            : null}
          <button
            type="button"
            onClick={() => setExpanded((v) => !v)}
            className="block w-[calc(100%+1rem)] -mx-2 rounded-md px-2 py-1.5 text-left text-[11px] text-muted-foreground hover:bg-accent/50 hover:text-foreground transition-colors"
          >
            {expanded
              ? t(($) => $.detail.pull_request_card_show_less)
              : t(($) => $.detail.pull_request_card_show_more, { count: collapsedTail.length })}
          </button>
        </div>
      ) : null}
    </div>
  );
}

function PullRequestRow({ pr }: { pr: GitHubPullRequest }) {
  const { t } = useT("issues");
  const cfg = STATE_ICON[pr.state] ?? { icon: GitPullRequest, className: "" };
  const StateIcon = cfg.icon;
  const kind = derivePullRequestStatusKind({
    state: pr.state,
    mergeable_state: pr.mergeable_state,
    checks_failed: pr.checks_failed,
    checks_pending: pr.checks_pending,
    checks_passed: pr.checks_passed,
  });
  const segments = derivePullRequestProgressSegments({
    state: pr.state,
    checks_failed: pr.checks_failed,
    checks_pending: pr.checks_pending,
    checks_passed: pr.checks_passed,
  });
  const showStats = shouldShowPullRequestStats({
    additions: pr.additions,
    deletions: pr.deletions,
    changed_files: pr.changed_files,
  });
  const statusText = useStatusText(kind);
  const draftPrefix = pr.state === "draft";
  const stateLabel = getStateLabel(pr.state, t);

  return (
    <a
      data-testid="pull-request-row"
      href={pr.html_url}
      target="_blank"
      rel="noreferrer noopener"
      className={cn(
        "flex items-start gap-2 rounded-md px-2 py-1.5 -mx-2 hover:bg-accent/50 transition-colors group",
        draftPrefix ? "opacity-80" : null,
      )}
    >
      <StateIcon className={cn("h-3.5 w-3.5 mt-0.5 shrink-0", cfg.className)} />
      <div className="min-w-0 flex-1">
        <p className="text-xs font-medium leading-snug truncate group-hover:text-foreground">
          {pr.title}
        </p>
        <p className="text-[11px] text-muted-foreground truncate">
          {pr.repo_owner}/{pr.repo_name}#{pr.number} · {stateLabel}
          {pr.author_login ? ` · @${pr.author_login}` : null}
        </p>
        <PullRequestRowDetails
          pr={pr}
          segments={segments}
          showStats={showStats}
          statusText={
            draftPrefix
              ? t(($) => $.detail.pull_request_card_draft_prefix, { status: statusText })
              : statusText
          }
          statusKind={kind}
        />
      </div>
    </a>
  );
}

function PullRequestRowDetails({
  pr,
  segments,
  showStats,
  statusText,
  statusKind,
}: {
  pr: GitHubPullRequest;
  segments: PullRequestProgressSegment[] | null;
  showStats: boolean;
  statusText: string;
  statusKind: PullRequestStatusKind;
}) {
  const { t } = useT("issues");
  const checksBadge = getChecksBadge(pr, t);
  const conflictsBadge = getConflictsBadge(pr, t);
  const isTerminal = statusKind === "closed" || statusKind === "merged";
  const showChecksBadge =
    !isTerminal &&
    !!checksBadge &&
    statusKind !== "checks_failed" &&
    statusKind !== "checks_pending" &&
    statusKind !== "checks_passed";
  const showConflictsBadge =
    !isTerminal && !!conflictsBadge && statusKind !== "conflicts" && statusKind !== "ready";

  return (
    <div className="mt-1 flex flex-wrap items-center gap-x-2 gap-y-0.5 text-[11px] text-muted-foreground">
      {showStats ? <PullRequestStats pr={pr} /> : null}
      <PullRequestProgressStrip segments={segments} />
      <span className="truncate">{statusText}</span>
      {showChecksBadge ? <PullRequestBadge badge={checksBadge} /> : null}
      {showConflictsBadge ? <PullRequestBadge badge={conflictsBadge} /> : null}
    </div>
  );
}

function PullRequestStats({ pr }: { pr: GitHubPullRequest }) {
  const { t } = useT("issues");
  return (
    <span className="inline-flex items-center gap-1.5 tabular-nums">
      <span className="text-emerald-600 dark:text-emerald-400">+{pr.additions ?? 0}</span>
      <span className="text-rose-600 dark:text-rose-400">−{pr.deletions ?? 0}</span>
      <span aria-hidden="true">·</span>
      <span>
        {t(($) => $.detail.pull_request_card_files_count, {
          count: pr.changed_files ?? 0,
        })}
      </span>
    </span>
  );
}

function PullRequestProgressStrip({
  segments,
}: {
  segments: PullRequestProgressSegment[] | null;
}) {
  if (!segments) return null;
  return (
    <span className="flex h-1 w-12 shrink-0 overflow-hidden rounded-full bg-muted" aria-hidden="true">
      {segments.map((seg) => (
        <span
          key={seg.kind}
          className={cn(
            "h-full block",
            seg.kind === "failed" && "bg-rose-500 dark:bg-rose-400",
            seg.kind === "pending" && "bg-amber-500 dark:bg-amber-400",
            seg.kind === "passed" && "bg-emerald-500 dark:bg-emerald-400",
          )}
          style={{ width: `${seg.ratio * 100}%` }}
        />
      ))}
    </span>
  );
}

interface PullRequestBadgeConfig {
  icon: React.ComponentType<{ className?: string }>;
  label: string;
  className: string;
}

function PullRequestBadge({ badge }: { badge: PullRequestBadgeConfig }) {
  const Icon = badge.icon;
  return (
    <span className="inline-flex items-center gap-1">
      <Icon className={cn("h-3 w-3", badge.className)} />
      {badge.label}
    </span>
  );
}

function getConflictsBadge(
  pr: GitHubPullRequest,
  t: IssuesT,
): PullRequestBadgeConfig | null {
  const mergeable = pr.mergeable_state ?? null;
  return mergeable === "dirty"
    ? {
        icon: TriangleAlert,
        label: t(($) => $.detail.pull_request_conflicts_dirty),
        className: "text-rose-600 dark:text-rose-400",
      }
    : mergeable === "clean"
      ? {
          icon: CheckCircle2,
          label: t(($) => $.detail.pull_request_conflicts_clean),
          className: "text-emerald-600 dark:text-emerald-400",
        }
      : null;
}

function getChecksBadge(
  pr: GitHubPullRequest,
  t: IssuesT,
): PullRequestBadgeConfig | null {
  const checks = pr.checks_conclusion ?? null;
  return checks && CHECKS_ICON[checks]
    ? {
        icon: CHECKS_ICON[checks].icon,
        className: CHECKS_ICON[checks].className,
        label:
          checks === "passed"
            ? t(($) => $.detail.pull_request_checks_passed)
            : checks === "failed"
              ? t(($) => $.detail.pull_request_checks_failed)
              : t(($) => $.detail.pull_request_checks_pending),
      }
    : null;
}

function getStateLabel(
  state: GitHubPullRequestState,
  t: IssuesT,
): string {
  return state === "open"
    ? t(($) => $.detail.pull_request_state_open)
    : state === "draft"
      ? t(($) => $.detail.pull_request_state_draft)
      : state === "merged"
        ? t(($) => $.detail.pull_request_state_merged)
        : state === "closed"
          ? t(($) => $.detail.pull_request_state_closed)
          : state;
}

function useStatusText(kind: PullRequestStatusKind): string {
  const { t } = useT("issues");
  switch (kind) {
    case "closed":
      return t(($) => $.detail.pull_request_card_status_closed);
    case "merged":
      return t(($) => $.detail.pull_request_card_status_merged);
    case "conflicts":
      return t(($) => $.detail.pull_request_card_status_conflicts);
    case "checks_failed":
      return t(($) => $.detail.pull_request_card_status_checks_failed);
    case "checks_pending":
      return t(($) => $.detail.pull_request_card_status_checks_pending);
    case "checks_passed":
      return t(($) => $.detail.pull_request_card_status_checks_passed);
    case "ready":
      return t(($) => $.detail.pull_request_card_status_ready);
    case "unknown":
      return t(($) => $.detail.pull_request_card_status_unknown);
  }
}