"use client";

// allow: SIZE_OK — the course state machine keeps its rAF loop and submission lifecycle together.

import { useCallback, useEffect, useRef, useState, type PointerEvent } from "react";
import { useRouter } from "next/navigation";
import { Crosshair, RotateCcw, Target, Timer, Trophy } from "lucide-react";

import {
  AIM_TRAINER_DIFFICULTIES,
  calculateAimTrainerAccuracy,
  calculateAimTrainerScore,
  COURSE_DURATION_MS,
  HEADSHOT_POINTS,
  createAimTrainerTarget,
  resolveAimTrainerTargetHit,
  stepAimTrainerTarget,
  TORSO_POINTS,
  type AimTrainerDifficulty,
} from "@/lib/aim-trainer";
import {
  type AimTrainerResultInput,
  type AimTrainerStats,
  submitAimTrainerResult,
} from "@/app/(frontend)/qualification/actions";
import { LoginLink } from "@/components/frontend/auth/LoginLink";
import { Badge } from "@/components/ui/badge";
import { Button } from "@/components/ui/button";
import { Card, CardContent, CardDescription, CardHeader, CardTitle } from "@/components/ui/card";
import { PROFILE_UPDATE_EVENT } from "@/hooks/useGameTick";
import { useSessionExpired } from "@/hooks/useSessionExpired";
import { cn } from "@/lib/utils";
import {
  AIM_TRAINER_CANVAS_HEIGHT as CANVAS_H,
  AIM_TRAINER_CANVAS_WIDTH as CANVAS_W,
  AIM_TRAINER_FEEDBACK_DURATION_MS as FEEDBACK_DURATION_MS,
  AIM_TRAINER_FLASH_DURATION_MS as FLASH_DURATION_MS,
  createAimTrainerGameState,
  drawAimTrainerScene,
  emptyAimTrainerLiveStats,
  getAimTrainerLiveStats,
  type AimTrainerActiveTarget,
  type AimTrainerGameState,
  type AimTrainerLiveStats,
} from "./AimTrainerCanvas";
import {
  playCountdownTick,
  playFire,
  playHeadshot,
  playMiss,
  playRoundComplete,
  playTorsoHit,
  playXp,
} from "./sounds";

const FINAL_COUNTDOWN_WINDOW_MS = 10_000;
const CRITICAL_COUNTDOWN_WINDOW_MS = 3_000;
const MAX_FRAME_DT_SEC = 0.05;
const COURSE_DURATION_SECONDS = COURSE_DURATION_MS / 1000;

const TIER_META = {
  recruit: {
    label: "Recruit",
    description: "Stationary silhouettes with a forgiving acquisition window.",
  },
  veteran: {
    label: "Veteran",
    description: "A mixed range with faster movement and tighter hit zones.",
  },
  elite: {
    label: "Elite",
    description: "High-speed targets. Every sight picture matters.",
  },
} as const satisfies Record<
  AimTrainerDifficulty,
  { readonly label: string; readonly description: string }
>;

const TIER_SCORE_KEYS = {
  recruit: "recruitBestScore",
  veteran: "veteranBestScore",
  elite: "eliteBestScore",
} as const satisfies Record<
  AimTrainerDifficulty,
  "recruitBestScore" | "veteranBestScore" | "eliteBestScore"
>;

export type AimTrainerPhase = "ready" | "playing" | "over";

type LastRun = {
  readonly hitScore: number;
  readonly accuracyBonus: number;
  readonly totalScore: number;
  readonly accuracy: number;
  readonly headshots: number;
  readonly torsoHits: number;
  readonly shotsFired: number;
  readonly despawnedUnhitTargets: number;
  readonly xpEarned: number;
  readonly bestScore: number;
  readonly isNewRecord: boolean;
  readonly error?: string;
};

function assertNever(value: never): never {
  throw new Error(`Unexpected hit zone: ${String(value)}`);
}

function tierBestScore(stats: AimTrainerStats, difficulty: AimTrainerDifficulty): number {
  return stats[TIER_SCORE_KEYS[difficulty]];
}

function formatAccuracy(value: number): string {
  return `${Math.round(value * 100)}%`;
}

function HudMetric({
  label,
  value,
  urgent = false,
}: {
  label: string;
  value: string | number;
  urgent?: boolean;
}) {
  return (
    <div
      className={cn(
        "flex min-w-0 flex-col gap-1 rounded-md border border-border bg-background/70 px-3 py-2",
        urgent && "border-destructive/50 bg-destructive/10",
      )}
    >
      <span className="truncate text-xs font-medium uppercase tracking-wider text-muted-foreground">
        {label}
      </span>
      <span
        className={cn(
          "font-mono text-base font-semibold tabular-nums",
          urgent && "text-destructive",
        )}
      >
        {value}
      </span>
    </div>
  );
}

function SummaryMetric({ label, value }: { label: string; value: string | number }) {
  return (
    <div className="flex flex-col gap-0.5 rounded-md border border-border bg-background/60 px-3 py-2">
      <dt className="text-xs uppercase tracking-wider text-muted-foreground">{label}</dt>
      <dd className="font-mono text-sm font-semibold tabular-nums">{value}</dd>
    </div>
  );
}

export function AimTrainerGame({
  initialStats: serverStats,
  difficulty,
  onGameRecordedAction,
  onPhaseChangeAction,
}: {
  readonly initialStats: AimTrainerStats;
  readonly difficulty: AimTrainerDifficulty;
  readonly onGameRecordedAction?: (stats: AimTrainerStats) => void;
  readonly onPhaseChangeAction?: (phase: AimTrainerPhase) => void;
}) {
  const router = useRouter();
  const { expired, expiredRef } = useSessionExpired();
  const canvasRef = useRef<HTMLCanvasElement | null>(null);
  const wrapperRef = useRef<HTMLDivElement | null>(null);
  const phaseRef = useRef<AimTrainerPhase>("ready");
  const submittingRef = useRef(false);
  const statsRef = useRef<AimTrainerStats>(serverStats);
  const gameRef = useRef<AimTrainerGameState>(createAimTrainerGameState());
  const [phase, setPhase] = useState<AimTrainerPhase>("ready");
  const [timerSeconds, setTimerSeconds] = useState(COURSE_DURATION_SECONDS);
  const [live, setLive] = useState<AimTrainerLiveStats>(emptyAimTrainerLiveStats);
  const [stats, setStats] = useState<AimTrainerStats>(serverStats);
  const [lastRun, setLastRun] = useState<LastRun | null>(null);
  const [submitting, setSubmitting] = useState(false);
  const tier = TIER_META[difficulty];
  const config = AIM_TRAINER_DIFFICULTIES[difficulty];

  const setPhaseSafe = useCallback(
    (nextPhase: AimTrainerPhase) => {
      phaseRef.current = nextPhase;
      setPhase(nextPhase);
      onPhaseChangeAction?.(nextPhase);
    },
    [onPhaseChangeAction],
  );

  const handleRoundComplete = useCallback(
    async (round: AimTrainerResultInput) => {
      if (submittingRef.current) return;
      const hits = round.headshots + round.torsoHits;
      const accuracy = calculateAimTrainerAccuracy(
        hits,
        round.shotsFired,
        round.despawnedUnhitTargets,
      );
      const totalScore = calculateAimTrainerScore(
        round.headshots,
        round.torsoHits,
        round.shotsFired,
        round.despawnedUnhitTargets,
      );
      const hitScore = round.headshots * HEADSHOT_POINTS + round.torsoHits * TORSO_POINTS;
      const previousTierBest = tierBestScore(statsRef.current, difficulty);
      const preview: LastRun = {
        hitScore,
        accuracyBonus: Math.max(0, totalScore - hitScore),
        totalScore,
        accuracy,
        headshots: round.headshots,
        torsoHits: round.torsoHits,
        shotsFired: round.shotsFired,
        despawnedUnhitTargets: round.despawnedUnhitTargets,
        xpEarned: 0,
        bestScore: previousTierBest,
        isNewRecord: false,
      };
      setLastRun(preview);

      if (expiredRef.current) {
        setLastRun({ ...preview, error: "Your session expired. Result not recorded." });
        return;
      }

      submittingRef.current = true;
      setSubmitting(true);
      try {
        const result = await submitAimTrainerResult(round);
        if (result.success && result.data) {
          statsRef.current = result.data;
          setStats(result.data);
          onGameRecordedAction?.(result.data);
          if (result.data.xpEarned > 0) {
            playXp();
            window.dispatchEvent(
              new CustomEvent(PROFILE_UPDATE_EVENT, {
                detail: { reason: "xp", xpGained: result.data.xpEarned },
              }),
            );
            window.setTimeout(() => router.refresh(), 1700);
          }
          setLastRun({
            ...preview,
            accuracy: result.data.accuracy,
            accuracyBonus: Math.max(0, result.data.score - hitScore),
            totalScore: result.data.score,
            xpEarned: result.data.xpEarned,
            bestScore: tierBestScore(result.data, difficulty),
            isNewRecord: result.data.score > previousTierBest,
          });
        } else {
          setLastRun({ ...preview, error: result.error ?? "Could not record qualification." });
        }
      } catch (error) {
        const message = error instanceof Error ? error.message : "Could not record qualification.";
        setLastRun({ ...preview, error: message });
      } finally {
        submittingRef.current = false;
        setSubmitting(false);
      }
    },
    [difficulty, expiredRef, onGameRecordedAction, router],
  );

  const handleRoundCompleteRef = useRef(handleRoundComplete);
  useEffect(() => {
    handleRoundCompleteRef.current = handleRoundComplete;
  }, [handleRoundComplete]);

  const resetToReady = useCallback(() => {
    if (expiredRef.current || submittingRef.current) return;
    gameRef.current = createAimTrainerGameState();
    setLive(emptyAimTrainerLiveStats());
    setTimerSeconds(COURSE_DURATION_SECONDS);
    setLastRun(null);
    setPhaseSafe("ready");
  }, [expiredRef, setPhaseSafe]);

  const startGame = useCallback(() => {
    if (expiredRef.current || submittingRef.current) return;
    const now = performance.now();
    const game = createAimTrainerGameState();
    game.pendingSpawnAts = Array.from(
      { length: config.maxConcurrentTargets },
      (_, index) => now + index * config.replacementDelayMs,
    );
    game.startedAt = now;
    gameRef.current = game;
    setLive(emptyAimTrainerLiveStats());
    setTimerSeconds(COURSE_DURATION_SECONDS);
    setLastRun(null);
    setPhaseSafe("playing");
    wrapperRef.current?.focus({ preventScroll: true });
  }, [config.maxConcurrentTargets, config.replacementDelayMs, expiredRef, setPhaseSafe]);

  const handlePrimaryAction = useCallback(() => {
    const currentPhase = phaseRef.current;
    switch (currentPhase) {
      case "ready":
        startGame();
        return;
      case "playing":
        return;
      case "over":
        resetToReady();
        return;
      default:
        assertNever(currentPhase);
    }
  }, [resetToReady, startGame]);

  const handleRestartAction = useCallback(() => {
    if (phaseRef.current !== "playing") return;
    startGame();
  }, [startGame]);

  const handleShot = useCallback(
    (event: PointerEvent<HTMLCanvasElement>) => {
      if (event.button !== 0 || phaseRef.current !== "playing") return;
      if (expiredRef.current || submittingRef.current) return;
      event.preventDefault();
      wrapperRef.current?.focus({ preventScroll: true });

      const canvas = canvasRef.current;
      if (!canvas) return;
      const rect = canvas.getBoundingClientRect();
      const x = ((event.clientX - rect.left) / rect.width) * CANVAS_W;
      const y = ((event.clientY - rect.top) / rect.height) * CANVAS_H;
      const game = gameRef.current;
      const now = performance.now();
      game.shotsFired += 1;
      playFire();

      const hit = resolveAimTrainerTargetHit(
        game.targets.map((activeTarget) => activeTarget.target),
        x,
        y,
      );
      if (!hit) {
        playMiss();
        game.feedback.push({ x, y, text: "MISS", color: "#b8b49c", createdAt: now });
        setLive(getAimTrainerLiveStats(game));
        return;
      }

      const [activeTarget] = game.targets.splice(hit.index, 1);
      if (!activeTarget) return;
      const target = activeTarget.target;
      game.pendingSpawnAts.push(now + config.replacementDelayMs);
      switch (hit.zone) {
        case "head":
          game.headshots += 1;
          game.feedback.push({
            x: target.x,
            y: target.y - target.headRadius,
            text: `+${HEADSHOT_POINTS}`,
            color: "#f0e6a8",
            createdAt: now,
          });
          game.flashColor = "#e5d98a";
          game.flashUntil = now + FLASH_DURATION_MS;
          playHeadshot();
          break;
        case "torso":
          game.torsoHits += 1;
          game.feedback.push({
            x: target.x,
            y: target.y + target.torsoH * 0.45,
            text: `+${TORSO_POINTS}`,
            color: "#c8c59d",
            createdAt: now,
          });
          game.flashColor = "#aaa878";
          game.flashUntil = now + FLASH_DURATION_MS;
          playTorsoHit();
          break;
        default:
          assertNever(hit.zone);
      }
      setLive(getAimTrainerLiveStats(game));
    },
    [config.replacementDelayMs, expiredRef],
  );

  useEffect(() => {
    const canvas = canvasRef.current;
    if (!canvas) return;
    const dpr = window.devicePixelRatio || 1;
    canvas.width = CANVAS_W * dpr;
    canvas.height = CANVAS_H * dpr;
    const ctx = canvas.getContext("2d");
    if (!ctx) return;
    ctx.setTransform(dpr, 0, 0, dpr, 0, 0);

    let raf = 0;
    let lastTime = performance.now();

    const finish = () => {
      const game = gameRef.current;
      if (phaseRef.current !== "playing") return;
      game.targets = [];
      game.pendingSpawnAts = [];
      setTimerSeconds(0);
      setLive(getAimTrainerLiveStats(game));
      setPhaseSafe("over");
      playRoundComplete();
      void handleRoundCompleteRef.current({
        difficulty,
        headshots: game.headshots,
        torsoHits: game.torsoHits,
        shotsFired: game.shotsFired,
        despawnedUnhitTargets: game.despawnedUnhitTargets,
      });
    };

    const step = (now: number) => {
      raf = requestAnimationFrame(step);
      const dtSec = Math.min(Math.max((now - lastTime) / 1000, 0), MAX_FRAME_DT_SEC);
      lastTime = now;
      const game = gameRef.current;

      if (phaseRef.current === "playing") {
        const elapsed = now - game.startedAt;
        const remaining = Math.max(0, COURSE_DURATION_MS - elapsed);
        if (remaining === 0) {
          finish();
        } else {
          const displayedSecond =
            remaining <= FINAL_COUNTDOWN_WINDOW_MS
              ? Math.ceil(remaining / 1000)
              : COURSE_DURATION_SECONDS;
          if (displayedSecond !== game.lastDisplayedSecond) {
            game.lastDisplayedSecond = displayedSecond;
            setTimerSeconds(displayedSecond);
            if (remaining <= CRITICAL_COUNTDOWN_WINDOW_MS) playCountdownTick(true);
            else if (remaining <= FINAL_COUNTDOWN_WINDOW_MS) playCountdownTick();
          }

          const survivingTargets: AimTrainerActiveTarget[] = [];
          let expiredTargets = 0;
          for (const activeTarget of game.targets) {
            if (now - activeTarget.spawnedAt >= config.targetLifetimeMs) {
              expiredTargets += 1;
              game.pendingSpawnAts.push(now + config.replacementDelayMs);
              continue;
            }
            survivingTargets.push({
              target: stepAimTrainerTarget(activeTarget.target, dtSec, CANVAS_W, CANVAS_H),
              spawnedAt: activeTarget.spawnedAt,
            });
          }
          game.targets = survivingTargets;
          if (expiredTargets > 0) {
            game.despawnedUnhitTargets += expiredTargets;
            setLive(getAimTrainerLiveStats(game));
          }

          while (game.targets.length < config.maxConcurrentTargets) {
            const dueIndex = game.pendingSpawnAts.findIndex((spawnAt) => spawnAt <= now);
            if (dueIndex === -1) break;
            game.pendingSpawnAts.splice(dueIndex, 1);
            game.targets.push({
              target: createAimTrainerTarget(Math.random, CANVAS_W, CANVAS_H, difficulty),
              spawnedAt: now,
            });
          }
        }
      }

      game.feedback = game.feedback.filter((item) => now - item.createdAt < FEEDBACK_DURATION_MS);
      drawAimTrainerScene(ctx, game, {
        now,
        targetLifetimeMs: config.targetLifetimeMs,
      });
    };

    raf = requestAnimationFrame(step);
    const onKeyDown = (event: KeyboardEvent) => {
      if (event.code === "KeyR") {
        if (event.repeat || event.ctrlKey || event.metaKey || event.altKey) return;
        event.preventDefault();
        event.stopPropagation();
        handleRestartAction();
        return;
      }
      if (event.code !== "Enter" && event.code !== "Space") return;
      if (event.repeat) return;
      event.preventDefault();
      event.stopPropagation();
      handlePrimaryAction();
    };
    const onKeyUp = (event: KeyboardEvent) => {
      if (event.code !== "Space") return;
      event.preventDefault();
      event.stopPropagation();
    };
    window.addEventListener("keydown", onKeyDown, { capture: true });
    window.addEventListener("keyup", onKeyUp, { capture: true });

    return () => {
      cancelAnimationFrame(raf);
      window.removeEventListener("keydown", onKeyDown, { capture: true });
      window.removeEventListener("keyup", onKeyUp, { capture: true });
    };
  }, [
    config.replacementDelayMs,
    config.maxConcurrentTargets,
    config.targetLifetimeMs,
    difficulty,
    handlePrimaryAction,
    handleRestartAction,
    setPhaseSafe,
  ]);

  const timerIsCritical = phase === "playing" && timerSeconds <= 3;
  const timerLabel = phase === "ready" ? `${COURSE_DURATION_SECONDS}s` : `${timerSeconds}s`;

  return (
    <Card className="w-full max-w-3xl overflow-hidden">
      <CardHeader className="gap-3 border-b border-border">
        <div className="flex flex-wrap items-start justify-between gap-3">
          <div className="flex items-start gap-3">
            <div className="rounded-md border border-border bg-background p-2 text-primary">
              <Crosshair aria-hidden="true" className="size-5" />
            </div>
            <div className="flex flex-col gap-1">
              <CardTitle>Live-fire qualification</CardTitle>
              <CardDescription>{tier.description}</CardDescription>
            </div>
          </div>
          <Badge variant={timerIsCritical ? "destructive" : "outline"}>
            <Timer data-icon="inline-start" />
            {timerLabel}
          </Badge>
        </div>
        <div className="grid grid-cols-2 gap-2 sm:grid-cols-3 lg:grid-cols-5" aria-live="polite">
          <HudMetric label="Score" value={live.score} />
          <HudMetric label="Accuracy" value={formatAccuracy(live.accuracy)} />
          <HudMetric label="Shots" value={live.shotsFired} />
          <HudMetric label="Tier" value={tier.label} />
          <HudMetric label="Time" value={timerLabel} urgent={timerIsCritical} />
        </div>
      </CardHeader>

      <CardContent className="flex flex-col gap-4 p-4">
        <div
          ref={wrapperRef}
          tabIndex={-1}
          className="relative mx-auto w-full cursor-crosshair select-none overflow-hidden rounded-lg border border-border bg-background outline-none focus-visible:ring-2 focus-visible:ring-ring"
        >
          <canvas
            ref={canvasRef}
            width={CANVAS_W}
            height={CANVAS_H}
            onPointerDown={handleShot}
            className="block h-auto w-full"
            aria-label="Qualification Course target range"
          />

          {phase === "ready" && (
            <div className="absolute inset-0 flex flex-col items-center justify-center gap-3 bg-background/75 p-4 text-center">
              <Badge variant="outline">{tier.label} lane</Badge>
              <div className="flex flex-col gap-1">
                <span className="text-lg font-semibold tracking-wide text-foreground">
                  Ready on the line
                </span>
                <span className="text-sm text-muted-foreground">
                  Acquire every silhouette before it clears the range.
                </span>
              </div>
              <Button
                type="button"
                className="motion-reduce:transition-none"
                onClick={startGame}
                disabled={expired || submitting}
              >
                <Target data-icon="inline-start" />
                Begin Qualification
              </Button>
              <span className="text-xs text-muted-foreground">
                Click the target or press Enter / Space to begin. Course duration:{" "}
                {COURSE_DURATION_SECONDS}s.
              </span>
            </div>
          )}

          {phase === "over" && lastRun && (
            <div className="absolute inset-0 flex flex-col justify-center gap-3 overflow-y-auto bg-background/90 p-4 text-center">
              <div className="flex items-center justify-center gap-2">
                <Trophy aria-hidden="true" className="size-5 text-primary" />
                <span className="text-lg font-semibold tracking-wide">Course complete</span>
              </div>
              {lastRun.isNewRecord && <Badge className="mx-auto">New record!</Badge>}
              <dl className="mx-auto grid w-full max-w-xl grid-cols-2 gap-2 text-left sm:grid-cols-3">
                <SummaryMetric label="Hit score" value={lastRun.hitScore} />
                <SummaryMetric label="Accuracy bonus" value={`+${lastRun.accuracyBonus}`} />
                <SummaryMetric label="Total score" value={lastRun.totalScore} />
                <SummaryMetric label="Accuracy" value={formatAccuracy(lastRun.accuracy)} />
                <SummaryMetric label="Headshots" value={lastRun.headshots} />
                <SummaryMetric label="Torso hits" value={lastRun.torsoHits} />
              </dl>
              <div className="flex flex-wrap items-center justify-center gap-x-4 gap-y-1 text-xs text-muted-foreground">
                <span>{lastRun.shotsFired} shots fired</span>
                <span>{lastRun.despawnedUnhitTargets} targets expired</span>
                <span className="font-semibold text-primary">+{lastRun.xpEarned} XP</span>
              </div>
              {lastRun.error && <span className="text-xs text-destructive">{lastRun.error}</span>}
              {submitting && (
                <span className="text-xs text-muted-foreground">Recording result…</span>
              )}
              <Button
                type="button"
                variant="outline"
                className="mx-auto motion-reduce:transition-none"
                onClick={resetToReady}
                disabled={submitting || expired}
              >
                <RotateCcw data-icon="inline-start" />
                Play Again
              </Button>
              <span className="text-xs text-muted-foreground">
                Press Enter or Space to return to the line.
              </span>
            </div>
          )}

          {expired && (
            <div className="absolute inset-0 flex flex-col items-center justify-center gap-3 bg-background/95 p-4 text-center">
              <span className="text-xl font-semibold tracking-wide text-destructive">
                Session ending soon
              </span>
              <span className="max-w-md text-sm text-muted-foreground">
                Your result will not be recorded after the session expires. Log in again to
                continue.
              </span>
              <LoginLink>
                <Button type="button" size="sm" className="motion-reduce:transition-none">
                  Log in
                </Button>
              </LoginLink>
            </div>
          )}
        </div>

        <div className="flex flex-wrap justify-center gap-x-6 gap-y-1 text-sm text-muted-foreground">
          <div className="flex items-center gap-1.5">
            <span>Games</span>
            <span className="font-semibold text-foreground">{stats.gamesPlayed}</span>
          </div>
          <div className="flex items-center gap-1.5">
            <span>Best score</span>
            <span className="font-semibold text-foreground">{stats.bestScore}</span>
          </div>
          <div className="flex items-center gap-1.5">
            <span>{tier.label} best</span>
            <span className="font-semibold text-foreground">
              {tierBestScore(stats, difficulty)}
            </span>
          </div>
          <div className="flex items-center gap-1.5">
            <span>XP from the course</span>
            <span className="font-semibold text-foreground">{stats.aimTrainerXp}</span>
          </div>
        </div>
        <div className="text-xs text-muted-foreground">
          Headshots score {HEADSHOT_POINTS}. Torso hits score {TORSO_POINTS}.
        </div>
      </CardContent>
    </Card>
  );
}