import { useEffect, useEffectEvent, useId, useRef, useState, type SubmitEvent } from "react";
import { useTranslation } from "react-i18next";
import { useQueryClient } from "@tanstack/react-query";
import { Crop, Crosshair, Maximize, Minus, Plus, Repeat, Scissors, X } from "lucide-react";
import { api, type ClipRequest } from "../../lib/api";
import { DISPLAY_NAME_MAX } from "../../lib/api/downloads";
import { invalidateDownloads } from "../../lib/downloads";
import { notify } from "../../lib/notifications";
import { notifyActionError } from "../../lib/actionErrors";
import { showInTray } from "../../lib/downloadQueue";
import { log } from "../../lib/log";
import { formatTimecode } from "../../lib/timecode";
import { handleBounds, markIn, markOut, zoomWindow, type ClipRange } from "../../lib/clipRange";
import { fitRatio, fracRatio, WHOLE, type Frac } from "../../lib/cropGeometry";
import { RangeTrack, RulerTicks, type RangeWindow } from "../../components/ui/RangeTrack";
import { CropFrame } from "../../components/ui/CropFrame";
import SegmentedToggle from "../../components/ui/SegmentedToggle";
import { Button } from "../../components/ui/Button";
import { IconButton } from "../../components/ui/IconButton";
import { Input } from "../../components/ui/Input";
import { TimecodeError, TimecodeField } from "../../components/ui/TimecodeField";
import { useTimecodeField, type TimecodeDraft } from "../../components/ui/useTimecodeField";

// The clip panel: marks a range of what is playing and cuts it into a download of its own. It lives
// IN the player (the YouTube card under the video, the Plex player's control band), so the video
// being watched is the preview: dragging a handle or pressing a timeline moves the player there.
//
// Two tracks: the whole item, with the selection and the zoomed window on it, and a zoomed strip
// around the selection where the handles are. The strip's window follows the selection when it
// settles, not while a handle is being dragged — a window that moved under the pointer would run
// away from the drag. A film is hours long and a clip seconds: only the strip gives a hand the
// precision, and the fields and their tenth-of-a-second steps give the rest.
//
// The range itself is the caller's state (`clip`), so the player's `[` / `]` keys and this panel
// mark the same range by the same rules (lib/clipRange).
//
// A clip is the whole picture unless the user turns the crop on: then a frame over the video
// (`ClipCropFrame`, which the player places over its picture) marks the part to keep, free or held
// to an output shape. The crop is the caller's state too, so the player's Escape can turn it off
// before it closes the panel.

/** The output shapes a crop frame can be held to (width / height of the clip), or a free frame. */
type ClipShape = "free" | "16:9" | "9:16" | "1:1";
const SHAPES: Record<Exclude<ClipShape, "free">, number> = {
  "16:9": 16 / 9,
  "9:16": 9 / 16,
  "1:1": 1,
};

/** A clip's crop: the frame, in fractions of the picture, and the shape it is held to. */
export interface ClipCrop {
  rect: Frac;
  shape: ClipShape;
}

const CROP_START: ClipCrop = { rect: { x: 0.1, y: 0.1, w: 0.8, h: 0.8 }, shape: "free" };
const round4 = (v: number) => Math.round(v * 10_000) / 10_000;
const lockOf = (crop: ClipCrop, picture: number) =>
  crop.shape === "free" ? null : fracRatio(SHAPES[crop.shape], picture);

export interface ClipSource {
  source: ClipRequest["source"];
  ref: string;
  /** Plex: the audio track that is playing, which the clip carries. */
  audioTrack?: number | null;
}

interface Props {
  src: ClipSource;
  clip: ClipRange;
  onChange: (r: ClipRange) => void;
  duration: number;
  /** The player's position, live. */
  current: number;
  /** The shape (width / height) of the picture the crop frame is drawn on. */
  picture: number;
  crop: ClipCrop | null;
  onCrop: (c: ClipCrop | null) => void;
  /** Move the player; `final` false while a pointer still drags (a player whose seek is costly waits). */
  onSeek: (time: number, final: boolean) => void;
  /** Play from `time` (the loop's restart, and "Play selection"). */
  onPlayFrom: (time: number) => void;
  onClose: () => void;
}

const NUDGE_S = 0.1;
// How far short of the item's end a seek stops: a mark on the very end moves the player to its last
// moment, not past it. A player put at its end ENDS, and the item counts as finished — YouTube marks
// it watched and shows its end screen, a Plex position reads as the whole — while a mark there is only
// a place. (The players keep themselves and the clip open at an end while one is marked; this keeps
// the item unfinished.)
const LAST_MOMENT_S = 0.25;
// On the always-dark chrome the ends are white (a light theme's accent is a dark blue there, which
// all but vanished on the bar) and the playhead amber, so an end and the playhead are never confused.
// The media amber (`--media-mark`), not the theme's warn: a light theme's is dark on this bar. Every
// focus ring in the panel is that amber as well (media-scope re-points --focus), as the crop frame's
// is: the theme accent's ring was under 3:1 on the chrome.
const PLAYHEAD = "bg-media-mark";

export default function ClipPanel({
  src,
  clip,
  onChange,
  duration,
  current,
  picture,
  crop,
  onCrop,
  onSeek,
  onPlayFrom,
  onClose,
}: Props) {
  const { t } = useTranslation();
  const qc = useQueryClient();
  const rootRef = useRef<HTMLFormElement>(null);
  const [name, setName] = useState("");
  const [busy, setBusy] = useState(false);
  const [looping, setLooping] = useState(false);
  // The strip's window while a handle drags (null at rest: it follows the selection).
  const [frozen, setFrozen] = useState<RangeWindow | null>(null);
  const hours = duration >= 3600;
  const tc = (s: number) => formatTimecode(s, hours);
  const view = frozen ?? zoomWindow(clip, duration);
  const bounds = handleBounds(clip, duration);
  const length = clip.end - clip.start;

  // Opened from a button or a key, the panel takes the focus to its In handle: the button that
  // opened it is gone (its row is this panel now), and the arrows then move the mark at once. Without
  // scrolling there: the player's card is still fitting itself around the new panel at this point,
  // and a card that has to scroll (a short window) scrolled the top of the video out of sight.
  useEffect(() => {
    rootRef.current
      ?.querySelector<HTMLElement>('[data-handle="in"]')
      ?.focus({ preventScroll: true });
  }, []);

  // The crop turned off from its frame (Escape there): the frame took the focus with it, so it goes to
  // the Crop toggle rather than to <body>, where the player's dialog no longer holds it.
  const cropButtonRef = useRef<HTMLButtonElement>(null);
  const cropOn = crop != null;
  useEffect(() => {
    if (cropOn) return;
    const lost = document.activeElement == null || document.activeElement === document.body;
    if (lost) cropButtonRef.current?.focus();
  }, [cropOn]);

  // "Play selection" loops: past Out, back to In.
  const restart = useEffectEvent(() => onPlayFrom(clip.start));
  useEffect(() => {
    if (looping && current >= clip.end) restart();
  }, [looping, current, clip.end]);

  const seek = (time: number, final: boolean) =>
    onSeek(Math.max(0, Math.min(time, duration - LAST_MOMENT_S)), final);
  const moveIn = (time: number, final: boolean) => {
    setFrozen(final ? null : (frozen ?? view));
    const next = markIn(clip, time, duration);
    onChange(next);
    seek(next.start, final);
  };
  const moveOut = (time: number, final: boolean) => {
    setFrozen(final ? null : (frozen ?? view));
    const next = markOut(clip, time, duration);
    onChange(next);
    seek(next.end, final);
  };

  const inField = useTimecodeField(clip.start, hours, (v) => moveIn(v, true));
  const outField = useTimecodeField(clip.end, hours, (v) => moveOut(v, true));
  const timeErrorId = useId();
  const body: ClipRequest = {
    source: src.source,
    ref: src.ref,
    start_s: Math.round(clip.start * 1000) / 1000,
    end_s: Math.round(clip.end * 1000) / 1000,
    ...(src.audioTrack != null ? { audio_track: src.audioTrack } : {}),
    ...(crop
      ? {
          crop: {
            x: round4(crop.rect.x),
            y: round4(crop.rect.y),
            w: round4(crop.rect.w),
            h: round4(crop.rect.h),
            aspect: round4(picture),
          },
        }
      : {}),
    ...(name.trim() ? { display_name: name.trim() } : {}),
  };
  const submit = async (e: SubmitEvent<HTMLFormElement>) => {
    e.preventDefault();
    if (busy) return;
    setBusy(true);
    try {
      const job = await api.enqueueClip(body);
      invalidateDownloads(qc);
      log.info("clip.queued", "clip queued", { source: src.source, seconds: Math.round(length) });
      notify({
        level: "success",
        message: t("clip.queued"),
        action: { label: t("clip.view"), onClick: () => showInTray(job.id) },
      });
      onClose();
    } catch (err) {
      // A refusal the server explains (too long, quota) is already in the error dialog; a lost
      // connection or a 404 is not, and must not leave the panel looking as if nothing happened.
      notifyActionError(err, t("clip.failed"));
      setBusy(false);
    }
  };

  return (
    <form
      ref={rootRef}
      onSubmit={submit}
      aria-label={t("clip.title")}
      data-testid="clip-panel"
      className="media-scope flex flex-col gap-2 bg-media-chrome/95 px-3 py-2.5 text-sm"
      // The panel's own presses are not the video's (play/pause) nor the backdrop's (close).
      onClick={(e) => e.stopPropagation()}
    >
      <div className="flex items-center gap-3">
        <span className="flex shrink-0 items-center gap-1.5 font-medium">
          <Scissors className="h-4 w-4" aria-hidden="true" />
          {t("clip.title")}
        </span>
        <RangeTrack
          label={t("clip.overview")}
          duration={duration}
          playhead={current}
          playheadClassName={PLAYHEAD}
          onSeek={(time, final) => final && seek(time, true)}
          className="h-5 flex-1 cursor-pointer rounded-sm bg-white/15"
          regions={[
            {
              key: "window",
              start: view.from,
              end: view.to,
              className: "border-x border-white/50",
            },
            { key: "sel", start: clip.start, end: clip.end, className: "bg-accent/70" },
          ]}
        />
        <IconButton variant="overlay" size="sm" onClick={onClose} label={t("clip.close")}>
          <X />
        </IconButton>
      </div>

      <RangeTrack
        label={t("clip.strip")}
        duration={duration}
        view={view}
        playhead={current}
        playheadClassName={PLAYHEAD}
        onSeek={seek}
        className="h-14 cursor-pointer rounded-md bg-white/10 text-white/45"
        background={
          <RulerTicks view={view} format={(s) => formatTimecode(s, hours).replace(/\.\d$/, "")} />
        }
        regions={[
          {
            key: "sel",
            start: clip.start,
            end: clip.end,
            className: "bg-accent/25 border-y-2 border-accent",
          },
        ]}
        handles={[
          {
            id: "in",
            label: t("clip.in"),
            time: clip.start,
            ...bounds.in,
            valueText: tc(clip.start),
            step: NUDGE_S,
            bigStep: 1,
            onChange: moveIn,
            barClassName: "bg-white",
          },
          {
            id: "out",
            label: t("clip.out"),
            time: clip.end,
            ...bounds.out,
            valueText: tc(clip.end),
            step: NUDGE_S,
            bigStep: 1,
            onChange: moveOut,
            barClassName: "bg-white",
          },
        ]}
      />

      <div className="flex flex-wrap items-center gap-x-4 gap-y-2">
        <MarkField
          label={t("clip.in")}
          value={clip.start}
          field={inField}
          errorId={timeErrorId}
          onSet={(v) => moveIn(v, true)}
          nudge={NUDGE_S}
          hereLabel={t("clip.inHere")}
          onHere={() => moveIn(current, true)}
        />
        <MarkField
          label={t("clip.out")}
          value={clip.end}
          field={outField}
          errorId={timeErrorId}
          onSet={(v) => moveOut(v, true)}
          nudge={NUDGE_S}
          hereLabel={t("clip.outHere")}
          onHere={() => moveOut(current, true)}
        />
        <span className="tabular-nums text-muted" aria-live="polite">
          {t("clip.length", { length: formatTimecode(length) })}
        </span>
        <Button
          variant="overlay"
          size="sm"
          pressed={looping}
          icon={<Repeat />}
          onClick={() => {
            if (!looping) onPlayFrom(clip.start);
            setLooping(!looping);
          }}
        >
          {t("clip.loop")}
        </Button>
      </div>
      {(inField.invalid || outField.invalid) && <TimecodeError id={timeErrorId} hours={hours} />}

      <div className="flex flex-wrap items-center gap-2">
        <Button
          ref={cropButtonRef}
          variant="overlay"
          size="sm"
          pressed={crop != null}
          icon={<Crop />}
          onClick={() => onCrop(crop ? null : CROP_START)}
        >
          {t("clip.crop")}
        </Button>
        {crop && (
          <>
            <SegmentedToggle
              ariaLabel={t("clip.shape")}
              value={crop.shape}
              onChange={(shape) => {
                const next = { ...crop, shape };
                const lock = lockOf(next, picture);
                onCrop(lock == null ? next : { ...next, rect: fitRatio(crop.rect, lock) });
              }}
              options={[
                { value: "free", label: t("clip.shapeFree") },
                { value: "16:9", label: "16:9" },
                { value: "9:16", label: "9:16" },
                { value: "1:1", label: "1:1" },
              ]}
            />
            <Button
              variant="overlay"
              size="sm"
              icon={<Maximize />}
              onClick={() => onCrop({ rect: WHOLE, shape: "free" })}
            >
              {t("clip.whole")}
            </Button>
          </>
        )}
      </div>

      <div className="flex flex-wrap items-center gap-2">
        <Input
          size="sm"
          className="min-w-48 flex-1"
          value={name}
          maxLength={DISPLAY_NAME_MAX}
          onChange={(e) => setName(e.target.value)}
          placeholder={t("clip.namePlaceholder")}
          aria-label={t("clip.name")}
        />
        <Button variant="overlay" size="sm" onClick={onClose}>
          {t("common.cancel")}
        </Button>
        <Button type="submit" variant="primary" size="sm" loading={busy} icon={<Scissors />}>
          {t("clip.cut")}
        </Button>
      </div>
    </form>
  );
}

/** One end's field: the time typed (Enter or leaving the field sets it), a tenth back and forward,
 *  and "to the playhead". */
function MarkField({
  label,
  value,
  field,
  errorId,
  onSet,
  nudge,
  hereLabel,
  onHere,
}: {
  label: string;
  value: number;
  field: TimecodeDraft;
  errorId: string;
  onSet: (v: number) => void;
  nudge: number;
  hereLabel: string;
  onHere: () => void;
}) {
  const { t } = useTranslation();
  return (
    <div className="flex items-center gap-1" role="group" aria-label={label}>
      <span className="mr-1 text-muted">{label}</span>
      <IconButton
        variant="overlay"
        size="sm"
        onClick={() => onSet(value - nudge)}
        label={t("clip.earlier", { label })}
      >
        <Minus />
      </IconButton>
      <TimecodeField
        size="sm"
        className="w-24 text-center tabular-nums"
        field={field}
        errorId={errorId}
        aria-label={label}
      />
      <IconButton
        variant="overlay"
        size="sm"
        onClick={() => onSet(value + nudge)}
        label={t("clip.later", { label })}
      >
        <Plus />
      </IconButton>
      <IconButton variant="overlay" size="sm" onClick={onHere} label={hereLabel}>
        <Crosshair />
      </IconButton>
    </div>
  );
}

/** The clip's crop frame, over the player's picture box (the caller positions this layer over it). */
export function ClipCropFrame({
  picture,
  crop,
  onCrop,
}: {
  picture: number;
  crop: ClipCrop;
  onCrop: (c: ClipCrop) => void;
}) {
  return (
    <CropFrame
      aspect={picture}
      rect={crop.rect}
      ratio={lockOf(crop, picture)}
      onChange={(rect) => onCrop({ ...crop, rect })}
      className="z-base"
    />
  );
}