import type { EnvironmentId, PullRequestDetailView, PullRequestRef } from "@t3tools/contracts";
import {
  ArrowDownUpIcon,
  ChevronRightIcon,
  HammerIcon,
  MessageSquareIcon,
  SendIcon,
  UsersIcon,
} from "lucide-react";
import { useState, type ReactNode } from "react";

import { useAtomCommand } from "~/state/use-atom-command";
import { pullRequestEnvironment } from "~/state/pullRequests";
import { cn } from "~/lib/utils";
import { readLocalApi } from "~/localApi";
import { formatRelativeTimeLabel } from "~/timestampFormat";

import { Button } from "../ui/button";
import { Collapsible, CollapsiblePanel, CollapsibleTrigger } from "../ui/collapsible";
import { Textarea } from "../ui/textarea";
import { toastManager } from "../ui/toast";
import { Tooltip, TooltipPopup, TooltipTrigger } from "../ui/tooltip";
import {
  PullRequestActorLabel,
  PullRequestCheckStatusIcon,
  PullRequestMetaLine,
  pullRequestCheckStatusLabel,
} from "./pullRequestPresentation";
import { PullRequestReviewerPicker } from "./PullRequestReviewerPicker";
import { PullRequestActivityUnavailableState } from "./PullRequestActivityUnavailableState";
import {
  orderPullRequestComments,
  pullRequestFindingKey,
  type PullRequestFinding,
} from "./pullRequestDetail.logic";
import { PullRequestMarkdown } from "./PullRequestMarkdown";
import { PullRequestConversationGhost } from "./PullRequestGhosts";

function MetaRow({
  icon,
  label,
  children,
}: {
  icon: ReactNode;
  label: string;
  children: ReactNode;
}) {
  return (
    <div className="flex items-center gap-2 py-1.5 text-xs">
      <span className="flex w-24 shrink-0 items-center gap-1.5 text-muted-foreground">
        {icon}
        {label}
      </span>
      <span className="min-w-0 flex-1 text-foreground">{children}</span>
    </div>
  );
}

function Section({
  title,
  count,
  defaultOpen = true,
  actions,
  children,
}: {
  title: string;
  count?: number;
  defaultOpen?: boolean;
  /** Controls riding on the heading row itself. A sibling of the trigger, not a child of it —
      a button cannot hold a button — and only while open, since they act on what is shown. */
  actions?: ReactNode;
  children: ReactNode;
}) {
  const [open, setOpen] = useState(defaultOpen);
  return (
    <Collapsible open={open} onOpenChange={setOpen}>
      <div className="flex w-full items-center border-t border-border/60 pr-4">
        {/* Title first, chevron riding to its right, count last: the row reads as a heading
            with an affordance rather than a tree node. */}
        <CollapsibleTrigger className="flex min-w-0 flex-1 items-center gap-1.5 px-4 py-3 text-left text-sm font-medium">
          <span>{title}</span>
          <ChevronRightIcon
            aria-hidden
            className={cn(
              "size-3.5 text-muted-foreground transition-transform",
              open && "rotate-90",
            )}
          />
          {count === undefined ? null : (
            <span className="text-xs tabular-nums text-muted-foreground">{count}</span>
          )}
        </CollapsibleTrigger>
        {open ? actions : null}
      </div>
      <CollapsiblePanel>
        <div className="px-4 pb-4">{children}</div>
      </CollapsiblePanel>
    </Collapsible>
  );
}

function CommentComposer({
  environmentId,
  detail,
  onCommented,
}: {
  environmentId: EnvironmentId;
  detail: PullRequestDetailView;
  onCommented: () => void;
}) {
  const [body, setBody] = useState("");
  const [posting, setPosting] = useState(false);
  const postComment = useAtomCommand(pullRequestEnvironment.comment, { reportFailure: false });

  const submit = async () => {
    const trimmed = body.trim();
    if (trimmed.length === 0 || posting) return;
    setPosting(true);
    const result = await postComment({
      environmentId,
      input: {
        projectId: detail.projectId,
        repository: detail.repository,
        number: detail.number,
        body: trimmed,
      },
    });
    setPosting(false);
    if (result._tag === "Failure") {
      toastManager.add({ type: "error", title: "Could not post the comment" });
      return;
    }
    setBody("");
    onCommented();
  };

  return (
    <div className="mt-3 space-y-2">
      <Textarea
        // Locked while posting: the body is cleared on success, which would otherwise throw
        // away a new draft typed while the request was still in flight.
        disabled={posting}
        value={body}
        rows={3}
        placeholder="Leave a comment"
        aria-label="Comment on this pull request"
        onChange={(event) => setBody(event.target.value)}
      />
      <div className="flex justify-end">
        <Button
          size="xs"
          variant="outline"
          disabled={body.trim().length === 0 || posting}
          onClick={() => void submit()}
        >
          <SendIcon className="size-3.5" />
          {posting ? "Posting..." : "Comment"}
        </Button>
      </div>
    </div>
  );
}

/**
 * What a first render of the conversation carries. A pull request with two hundred comments is
 * two hundred markdown documents, and the ones worth arriving for are the recent ones.
 */
const COMMENT_PAGE = 30;

export function PullRequestSummaryTab({
  environmentId,
  reference,
  detail,
  activityPending,
  activityError,
  pendingFinding,
  onFixFinding,
  onRefresh,
}: {
  environmentId: EnvironmentId;
  reference: PullRequestRef;
  detail: PullRequestDetailView;
  activityPending: boolean;
  activityError: string | null;
  /** The hand-off currently preparing, if any, so only the finding it belongs to says so. */
  pendingFinding?: string | null;
  onFixFinding?: (finding: PullRequestFinding) => void;
  onRefresh: () => void;
}) {
  // Keyed by the pull request, so opening another one starts at the end of its conversation
  // rather than wherever the last one had been read back to.
  const [shown, setShown] = useState({ url: detail.url, count: COMMENT_PAGE });
  const shownComments = shown.url === detail.url ? shown.count : COMMENT_PAGE;
  // Windowed by recency regardless of display order: expanding always reaches further back in
  // time, whether the newest comment currently reads first or last.
  const recentComments = detail.comments.slice(Math.max(0, detail.comments.length - shownComments));
  const hiddenCommentCount = detail.comments.length - recentComments.length;
  const [commentOrder, setCommentOrder] = useState<"newest" | "oldest">("newest");
  const visibleComments = orderPullRequestComments(recentComments, commentOrder);

  // A comment that already lives on a review thread is that thread: the thread carries the line
  // and side the bare comment has lost, and a resolved one is finished work nobody should be
  // invited to fix again — the same call the whole-review hand-off makes.
  const threadByCommentId = new Map(
    detail.reviewThreads.flatMap((thread) =>
      thread.comments.map((comment) => [comment.id, thread] as const),
    ),
  );

  const openCheck = (url: string) => {
    void readLocalApi()?.shell.openExternal(url);
  };

  return (
    <div className="h-full overflow-y-auto">
      <section className="px-4 py-3">
        <div>
          <MetaRow icon={<UsersIcon className="size-3.5" />} label="Reviewers">
            <span className="flex min-w-0 flex-wrap items-center gap-1.5">
              {detail.reviewers.length === 0 ? (
                <span className="text-muted-foreground">None</span>
              ) : (
                <span className="flex items-center -space-x-1">
                  {detail.reviewers.map((actor) => (
                    <Tooltip key={actor.login}>
                      <TooltipTrigger
                        render={
                          <span
                            className="relative rounded-full hover:z-10"
                            aria-label={actor.name ?? actor.login}
                          />
                        }
                      >
                        <PullRequestActorLabel
                          actor={actor}
                          className="gap-0 [&>img]:ring-2 [&>img]:ring-background [&>span:first-child]:ring-2 [&>span:first-child]:ring-background [&>span:last-child]:sr-only"
                        />
                      </TooltipTrigger>
                      <TooltipPopup side="bottom">
                        {actor.name && actor.name !== actor.login
                          ? `${actor.name} (@${actor.login})`
                          : actor.login}
                      </TooltipPopup>
                    </Tooltip>
                  ))}
                </span>
              )}
              {/* Shown wherever the host can take a review request at all, and disabled with the
                  reason where this account may not make one: a control that vanishes teaches
                  nobody why, and "you need write access" is the answer to the question a reader
                  actually has. Azure DevOps is the exception — it takes a reviewer but will not
                  say who could be one, so there is nothing to open. */}
              {detail.capabilities.reviewers.request &&
              detail.capabilities.reviewers.listCandidates ? (
                <PullRequestReviewerPicker
                  environmentId={environmentId}
                  reference={reference}
                  allowed={detail.viewerPermissions.requestReviewers}
                  onRequested={onRefresh}
                />
              ) : null}
            </span>
          </MetaRow>
          <MetaRow icon={<MessageSquareIcon className="size-3.5" />} label="Comments">
            {activityPending
              ? "Loading conversation…"
              : activityError
                ? "Conversation unavailable"
                : detail.commentCount === 1
                  ? "1 comment"
                  : `${detail.commentCount} comments`}
          </MetaRow>
        </div>
      </section>

      <Section title="Description">
        <PullRequestMarkdown
          text={detail.body.trim().length > 0 ? detail.body : "_No description provided._"}
          cwd={detail.workspaceRoot}
        />
      </Section>

      <Section title="Checks" count={detail.checks.length}>
        {detail.checks.length === 0 ? (
          <p className="text-xs text-muted-foreground">No checks reported.</p>
        ) : (
          <div className="space-y-0.5">
            {detail.checks.map((check) => {
              const finding = { kind: "check", check } as const;
              const failing = check.status === "failure" || check.status === "cancelled";
              return (
                <div
                  key={`${check.name}:${check.url ?? ""}`}
                  className="group flex items-center gap-1 rounded-md pr-1 hover:bg-accent/60"
                >
                  <button
                    type="button"
                    disabled={!check.url}
                    onClick={() => check.url && openCheck(check.url)}
                    className={cn(
                      "flex min-w-0 flex-1 items-center gap-2 rounded-md px-2 py-1.5 text-left text-xs",
                      check.url ? undefined : "cursor-default",
                    )}
                  >
                    <PullRequestCheckStatusIcon status={check.status} />
                    <span className="min-w-0 flex-1 truncate">{check.name}</span>
                    <span className="shrink-0 text-muted-foreground">
                      {pullRequestCheckStatusLabel(check.status)}
                    </span>
                  </button>
                  {/* Only where there is something to fix. A passing check has no failure to
                      reproduce, and the button would be an invitation to waste a thread. */}
                  {onFixFinding && failing ? (
                    <Button
                      size="xs"
                      variant="ghost"
                      className="shrink-0"
                      disabled={pendingFinding !== null && pendingFinding !== undefined}
                      onClick={() => onFixFinding(finding)}
                    >
                      <HammerIcon className="size-3" />
                      {pendingFinding === pullRequestFindingKey(finding) ? "Preparing..." : "Fix"}
                    </Button>
                  ) : null}
                </div>
              );
            })}
          </div>
        )}
      </Section>

      <Section
        title="Comments"
        {...(activityPending || activityError ? {} : { count: detail.commentCount })}
        actions={
          !activityPending && !activityError && detail.comments.length > 0 ? (
            <Button
              size="xs"
              variant="ghost"
              className="h-7 shrink-0 px-2 text-[10px] text-muted-foreground"
              aria-label={
                commentOrder === "newest"
                  ? "Show oldest comments first"
                  : "Show newest comments first"
              }
              onClick={() => setCommentOrder((value) => (value === "newest" ? "oldest" : "newest"))}
            >
              <ArrowDownUpIcon aria-hidden className="size-3" />
              {commentOrder === "newest" ? "Newest first" : "Oldest first"}
            </Button>
          ) : null
        }
      >
        {activityPending ? (
          <PullRequestConversationGhost />
        ) : activityError ? (
          <PullRequestActivityUnavailableState compact error={activityError} onRetry={onRefresh} />
        ) : (
          <>
            {detail.commentsTruncated ? (
              <p className="mb-2 rounded-md border border-amber-500/30 bg-amber-500/5 px-2 py-1.5 text-xs">
                This conversation is longer than this page reads in one go. The most recent{" "}
                {detail.comments.length} are here; open it on the host to read the rest.
              </p>
            ) : null}
            {detail.comments.length === 0 ? (
              <p className="py-2 text-xs text-muted-foreground">No comments yet.</p>
            ) : (
              <div className="space-y-3">
                {hiddenCommentCount > 0 ? (
                  // Hundreds of comments are hundreds of markdown renders, and the ones worth
                  // opening a pull request for are the recent ones. The rest are one press away and
                  // stay rendered once asked for.
                  <Button
                    size="sm"
                    variant="outline"
                    className="w-full"
                    onClick={() =>
                      setShown({ url: detail.url, count: shownComments + COMMENT_PAGE })
                    }
                  >
                    Show {Math.min(hiddenCommentCount, COMMENT_PAGE)} earlier{" "}
                    {hiddenCommentCount === 1 ? "comment" : "comments"}
                  </Button>
                ) : null}
                {visibleComments.map((comment) => {
                  const thread = threadByCommentId.get(comment.id);
                  const finding: PullRequestFinding | null =
                    comment.kind !== "review" && comment.kind !== "review-comment"
                      ? null
                      : thread === undefined
                        ? { kind: "comment", comment }
                        : thread.isResolved
                          ? null
                          : { kind: "thread", thread };
                  return (
                    <article
                      key={comment.id}
                      // Offscreen comments skip style, layout and paint. Bot comments carry pages of
                      // highlighted code, and the conversation is below the description either way.
                      className="rounded-lg border border-border/60 p-3 [contain-intrinsic-block-size:120px] [content-visibility:auto]"
                    >
                      <div className="flex items-start gap-2">
                        <PullRequestMetaLine className="min-w-0 flex-1 text-xs text-muted-foreground">
                          <PullRequestActorLabel
                            actor={comment.author}
                            className="font-medium text-foreground"
                          />
                          <span>{formatRelativeTimeLabel(comment.createdAt)}</span>
                          {comment.reviewState ? (
                            <span>{comment.reviewState.toLowerCase()}</span>
                          ) : null}
                        </PullRequestMetaLine>
                        {/* Review remarks only. A plain conversation comment is talk, not a finding,
                      and offering to fix one would promise more than it says. */}
                        {onFixFinding && finding ? (
                          <Button
                            size="xs"
                            variant="ghost"
                            className="-mt-1 shrink-0"
                            disabled={pendingFinding !== null && pendingFinding !== undefined}
                            onClick={() => onFixFinding(finding)}
                          >
                            <HammerIcon className="size-3" />
                            {pendingFinding === pullRequestFindingKey(finding)
                              ? "Preparing..."
                              : "Fix in a thread"}
                          </Button>
                        ) : null}
                      </div>
                      {comment.path ? (
                        <p
                          className="mt-1 truncate text-xs text-muted-foreground"
                          title={comment.path}
                        >
                          {comment.path}
                        </p>
                      ) : null}
                      <PullRequestMarkdown
                        className="mt-2"
                        text={comment.body}
                        cwd={detail.workspaceRoot}
                      />
                    </article>
                  );
                })}
              </div>
            )}
          </>
        )}
        {/* Posting is a core capability and remains usable even if the activity read failed. */}
        {detail.capabilities.comment && detail.viewerPermissions.comment ? (
          <CommentComposer
            key={`${environmentId}:${detail.projectId}/${detail.repository}#${detail.number}`}
            environmentId={environmentId}
            detail={detail}
            onCommented={onRefresh}
          />
        ) : null}
      </Section>
    </div>
  );
}