/** The whole app: one state object, one keydown listener for navigation, four screens.
 *
 * The same shape as ../../web/src/App.tsx - state lives here, components are layout, and
 * the keyboard is handled in one place rather than scattered through the tree.
 *
 * One rule is worth stating because it is easy to break later: **while a run is going,
 * every key belongs to the run**. Only Escape and F1 are intercepted here. Otherwise a
 * lesson that happens to teach `m` would mute the game every time she typed it, and the
 * mute would look to her like the game breaking. The run's own listener lives in
 * hooks/useRun.ts and does the typing; this one only handles the screens around it. */

import { useCallback, useEffect, useMemo, useRef, useState } from "react";

import { Aquarium } from "./components/Aquarium";
import { AppHeader } from "./components/AppHeader";
import { HelpOverlay } from "./components/HelpOverlay";
import { LessonMap } from "./components/LessonMap";
import { ModePicker } from "./components/ModePicker";
import { ResultSheet } from "./components/ResultSheet";
import { Stage } from "./components/Stage";
import { BubblesRun } from "./components/modes/BubblesRun";
import { FeedRun } from "./components/modes/FeedRun";
import { PearlsRun } from "./components/modes/PearlsRun";
import { JellyfishRun } from "./components/modes/JellyfishRun";
import { RaceRun } from "./components/modes/RaceRun";
import { DiveRun } from "./components/modes/DiveRun";
import type { CreatureId } from "./lib/aquarium";
import { LESSONS, lessonById, nextLesson } from "./lib/curriculum";
import type { Lesson, ModeId } from "./lib/curriculum";
import { lineFor, lineText, letterStream, mulberry32 } from "./lib/generator";
import type { RunResult } from "./lib/grading";
import { playFanfare, playPop } from "./lib/pop";
import { overallBestAnimal, focusKeyFor, loadProgress, recordRun, saveProgress } from "./lib/progress";
import type { Progress } from "./lib/progress";
import { bubbleCountFor } from "./lib/theme";

type Screen = "aquarium" | "map" | "run";

/** What a mode is handed to draw. Tagged rather than optional-fielded so the render
 * below narrows on `kind` instead of guessing from which keys are present.
 *
 * Only two shapes, for six modes: the arcade modes want a stream of single letters, and
 * everything else wants a line of chunks. That is the whole reason the modes are cheap
 * to add - they are presentations of one of two targets, all driven by the same engine. */
type RunTarget =
  | { kind: "letters"; letters: readonly string[] }
  | { kind: "text"; chunks: readonly string[]; text: string; spaceActive: boolean };

/** Modes that drill one key at a time rather than a line. */
const LETTER_ONLY_MODES: readonly ModeId[] = ["bubbles", "jellyfish"];

interface Outcome {
  result: RunResult;
  unlockedTitle: string | null;
  newCreature: CreatureId | null;
  isNewBest: boolean;
}

export function App() {
  const [progress, setProgress] = useState<Progress>(loadProgress);
  const [screen, setScreen] = useState<Screen>("aquarium");
  const [lessonId, setLessonId] = useState<string | null>(null);
  const [mode, setMode] = useState<ModeId>("dive");
  const [outcome, setOutcome] = useState<Outcome | null>(null);
  const [showHelp, setShowHelp] = useState(false);
  const [selected, setSelected] = useState(0);
  /** Bumped to generate a fresh line - a new seed for the same lesson. */
  const [round, setRound] = useState(0);

  useEffect(() => saveProgress(progress), [progress]);

  const lesson = lessonId === null ? null : lessonById(lessonId);

  /** The first lesson that is unlocked but not yet passed - where "Weiter üben" goes. */
  const nextUp = useMemo(() => {
    const unlocked = LESSONS.filter((l) => progress.lessons[l.id]?.unlocked);
    return unlocked.find((l) => (progress.lessons[l.id]?.bestStars ?? 0) < 2) ?? unlocked.at(-1) ?? null;
  }, [progress]);

  /** The line for this run. Reproducible from the lesson, the mode and the round
   * counter, so a re-render never reshuffles the text mid-run. */
  const run = useMemo((): RunTarget | null => {
    if (!lesson) return null;
    const seed = lesson.number * 1000 + round * 7 + (mode === "bubbles" ? 3 : 0);
    const rng = mulberry32(seed);
    const focusKey = focusKeyFor(progress, lesson.activeKeys);
    // Always a real space, even before the space-bar lesson formally teaches the thumb:
    // a gap she can see but not type is confusing, not gentle. See generator.ts.
    const spaceActive = true;

    if (LETTER_ONLY_MODES.includes(mode)) {
      return {
        kind: "letters",
        letters: letterStream(lesson.activeKeys, rng, bubbleCountFor(lesson.world), focusKey, lesson.newKeys),
      };
    }
    const chunks = lineFor(lesson, rng, {
      chunks: lesson.chunks,
      chunkSize: lesson.chunkSize,
      focusKey,
    });
    return { kind: "text", chunks, text: lineText(chunks, spaceActive), spaceActive };
    // `progress` is deliberately not a dependency: the focus key is read once when the
    // line is built, and re-reading it after every keystroke would rebuild the line
    // underneath her fingers.
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [lesson, mode, round]);

  const start = useCallback(
    (lesson: Lesson) => {
      setLessonId(lesson.id);
      setMode(lesson.modes.includes(mode) ? mode : "dive");
      setOutcome(null);
      setRound((r) => r + 1);
      setScreen("run");
    },
    [mode],
  );

  const onFinished = useCallback(
    (result: RunResult) => {
      if (!lessonId) return;
      const recorded = recordRun(progress, lessonId, result);
      setProgress(recorded.progress);
      setOutcome({
        result,
        unlockedTitle: recorded.unlockedLessonId
          ? (lessonById(recorded.unlockedLessonId)?.title ?? null)
          : null,
        newCreature: recorded.newCreature,
        isNewBest: recorded.isNewBest,
      });
      if (progress.settings.sound && (recorded.unlockedLessonId || recorded.newCreature)) {
        playFanfare();
      }
    },
    [lessonId, progress],
  );

  const retry = useCallback(() => {
    setOutcome(null);
    setRound((r) => r + 1);
  }, []);

  const continueAfterResult = useCallback(() => {
    const next = lessonId ? nextLesson(lessonId) : null;
    setOutcome(null);
    if (next && progress.lessons[next.id]?.unlocked) start(next);
    else setScreen("map");
  }, [lessonId, progress, start]);

  const goBack = useCallback(() => {
    if (outcome) return setOutcome(null);
    if (screen === "run") return setScreen("map");
    if (screen === "map") return setScreen("aquarium");
  }, [outcome, screen]);

  // --- navigation keys -----------------------------------------------------

  const latest = useRef({ screen, outcome, selected, goBack, retry, nextUp, start });
  latest.current = { screen, outcome, selected, goBack, retry, nextUp, start };

  useEffect(() => {
    const onKeyDown = (event: KeyboardEvent) => {
      const current = latest.current;

      if (event.key === "F1") {
        event.preventDefault();
        setShowHelp((open) => !open);
        return;
      }
      if (event.key === "Escape") {
        event.preventDefault();
        setShowHelp(false);
        current.goBack();
        return;
      }

      // Enter repeats a finished run; the result sheet's own button has focus, so this
      // is only a fallback for when focus has been lost.
      if (current.outcome) {
        if (event.key === "Enter") {
          event.preventDefault();
          current.retry();
        }
        return;
      }

      // Everything below is navigation, and must not fire while typing.
      if (current.screen === "run") return;

      if (event.key === "Enter") {
        event.preventDefault();
        if (current.screen === "aquarium") {
          if (current.nextUp) current.start(current.nextUp);
        } else {
          const lesson = LESSONS[current.selected];
          if (lesson) current.start(lesson);
        }
        return;
      }

      if (current.screen !== "map") return;
      const step =
        event.key === "ArrowRight" ? 1 : event.key === "ArrowLeft" ? -1 : 0;
      if (step !== 0) {
        event.preventDefault();
        playPop(340);
        setSelected((index) => Math.min(LESSONS.length - 1, Math.max(0, index + step)));
      }
    };

    window.addEventListener("keydown", onKeyDown);
    return () => window.removeEventListener("keydown", onKeyDown);
  }, []);

  // Settings keys live outside a run, where they cannot collide with the alphabet.
  useEffect(() => {
    const onKeyDown = (event: KeyboardEvent) => {
      if (screen === "run" && !outcome) return;
      const key = event.key.toLowerCase();
      if (key === "m") setProgress((p) => ({ ...p, settings: { ...p.settings, sound: !p.settings.sound } }));
      if (key === "h") {
        setProgress((p) => ({
          ...p,
          settings: {
            ...p.settings,
            keyboardHint: p.settings.keyboardHint === "off" ? "auto" : "off",
          },
        }));
      }
    };
    window.addEventListener("keydown", onKeyDown);
    return () => window.removeEventListener("keydown", onKeyDown);
  }, [screen, outcome]);

  // --- render --------------------------------------------------------------

  const next = lessonId ? nextLesson(lessonId) : null;

  // Every mode takes the same bundle; only the drawing differs. Built here so adding a
  // seventh mode is one line in the switch below rather than eight repeated props.
  const shared = {
    activeKeys: lesson?.activeKeys ?? [],
    progress,
    paused: outcome !== null,
    onFinished,
  };
  const letterProps = (letters: readonly string[]) => ({ letters, ...shared });
  const textProps = (r: Extract<RunTarget, { kind: "text" }>) => ({
    chunks: r.chunks,
    text: r.text,
    spaceActive: r.spaceActive,
    ...shared,
  });

  return (
    <Stage creatures={progress.aquarium} dimmed={screen === "run"}>
      <AppHeader
        title={screen === "run" && lesson ? lesson.title : "Delfin Tippen"}
        compact={screen === "run"}
        status={
          <div style={{ display: "flex", gap: 12, alignItems: "center", color: "var(--paper)", fontWeight: 800 }}>
            <span>🦪 {progress.pearls}</span>
            {!progress.settings.sound && <span title="Ton aus">🔇</span>}
          </div>
        }
      />

      {screen === "aquarium" && (
        <Aquarium
          progress={progress}
          nextLesson={nextUp}
          onContinue={() => nextUp && start(nextUp)}
          onOpenMap={() => setScreen("map")}
        />
      )}

      {screen === "map" && (
        <LessonMap progress={progress} selected={selected} onPick={start} />
      )}

      {screen === "run" && lesson && run && (
        <>
          {run.kind === "letters" ? (
            mode === "jellyfish" ? (
              <JellyfishRun {...letterProps(run.letters)} />
            ) : (
              <BubblesRun {...letterProps(run.letters)} />
            )
          ) : mode === "feed" ? (
            <FeedRun {...textProps(run)} />
          ) : mode === "pearls" ? (
            <PearlsRun {...textProps(run)} />
          ) : mode === "race" ? (
            <RaceRun {...textProps(run)} ghost={progress.lessons[lesson.id]?.ghost ?? null} />
          ) : (
            <DiveRun {...textProps(run)} />
          )}
          <div style={{ padding: "0 32px 18px", flex: "none" }}>
            <ModePicker
              modes={lesson.modes}
              active={mode}
              onPick={(chosen) => {
                setMode(chosen);
                setRound((r) => r + 1);
              }}
            />
          </div>
        </>
      )}

      {outcome && (
        <ResultSheet
          result={outcome.result}
          unlockedTitle={outcome.unlockedTitle}
          newCreature={outcome.newCreature}
          isNewBest={outcome.isNewBest}
          bestEver={overallBestAnimal(progress)}
          onRetry={retry}
          onContinue={continueAfterResult}
          continueLabel={
            next && progress.lessons[next.id]?.unlocked ? `${next.title} ▶` : "Zur Karte"
          }
        />
      )}

      {showHelp && <HelpOverlay onClose={() => setShowHelp(false)} />}
    </Stage>
  );
}