/* =============================================================================
 * D03_PlanAnalysis_UI_Draw.ts
 * D03 손 긋기 겹 · 그리기 칸(PLAN 562-3 · 요구서 389 3장 8~10) — 시점에서 점을 찍어 직선으로 이음.
 *
 *   본선 = D02 시점에서 · D02 종점 둘레(SNAP_PX)에 오면 종점에 붙고 그 점에서 끝.
 *   미리보기 = 마지막 점 → 마우스 길이(m) · 원지반 기울기(%, + 오르막) — 제약 칸 넷:
 *     자유 · 길이 고정 · 기울기 고정(마우스 방향 첫 자리) · 둘 다(양각기 원 위 후보 중 마우스에 가까운 것).
 *   갈래 = 기존 선 꺾임점(선 위면 꺾임점 끼움)을 눌러 시작 · 구역 마크 = 선 위 누름(오른쪽 = 지움).
 *   키 = Enter 끝 · Esc 이번 긋기 취소 · Backspace 마지막 점 빼기(설정 창 단축키 표 D03 줄).
 *   셈 = 562-1 짝(`logic/D03_PlanAnalysis_Draw`) · 꼴 다루기 = `logic/D03_PlanAnalysis_Plan` ·
 *   값을 바꾸면 `commit(다음 꼴)` 한 번 = 되돌리기 한 걸음(스택 · 캐시 = 페이지).
 * ========================================================================== */

import { createButton, showToast } from "@ui/ui_template_elements";
import { createInputField } from "@ui/ui_template_input";
import { createSegment } from "@ui/ui_template_segment";
import { createText } from "@ui/ui_template_text";
import { drawStationTicks } from "../B04_PreProcess/B04_PreProcess_UI_MapOverlays";
import {
  compassCandidates,
  compassPoint,
  distanceAlong,
  fixedLengthPoint,
  fixedSlopePoint,
  groundSlopePct,
  lineLength,
  pointAtDistance,
  segmentLength,
  stationChainages,
} from "./logic/D03_PlanAnalysis_Draw";
import {
  addBranch,
  appendVertex,
  dropLastLine,
  dropLastVertex,
  insertVertex,
  reachedEnd,
  removeMark,
  splitPiece,
  type PlanNetwork,
  type Vertex,
} from "./logic/D03_PlanAnalysis_Plan";
import {
  planColors,
  PLAN_STATION_INTERVAL_M,
  type PlanMapLayer,
  type ScreenMap,
} from "./D03_PlanAnalysis_UI_Map";

/** 종점 · 꺾임점에 붙는 반경(px). */
const SNAP_PX = 12;
/** 선 위 누름으로 볼 반경(px). */
const LINE_HIT_PX = 8;
/** 구간 길이 라벨을 보일 화면 길이(px). */
const LABEL_MIN_PX = 70;
/** 제약 칸 처음 값 — 길이 = 측점 간격(지식DB 설계제원_총괄) · 기울기 = 간선 20 km/h 일반지형 상한(종단선형). */
export const DRAW_DEFAULT_LENGTH_M = 20;
export const DRAW_DEFAULT_SLOPE_PCT = 9;

export type DrawConstraint = "free" | "length" | "slope" | "both";
export type DrawMode = "idle" | "draw" | "branch" | "mark";

export interface DrawPreview {
  point: Vertex;
  lengthM: number;
  slopePct: number | null;
  /** 붙음 · 자리 없음 안내(있으면 점을 못 찍음 = `blocked`). */
  note: string | null;
  blocked: boolean;
  snapped: boolean;
}

export interface PlanDrawParams {
  base: () => { start: Vertex; end: Vertex };
  network: () => PlanNetwork;
  heightAt: () => (x: number, y: number) => number;
  commit: (next: PlanNetwork) => void;
  /** 모드 · 그리는 선이 바뀜 — 페이지가 단추 · 안내를 다시. */
  onMode: () => void;
}

export interface PlanDraw {
  layer: PlanMapLayer;
  /** 좌측 「그리기」 칸 몸(모드 단추 · 제약 칸 · 안내). */
  panel: HTMLElement;
  mode: () => DrawMode;
  setMode: (mode: DrawMode) => void;
  setEditable: (editable: boolean) => void;
  /** 키 — 받았으면 참(Enter · Esc · Backspace). */
  key: (event: KeyboardEvent) => boolean;
  /** 되돌리기 뒤 — 그리던 선이 사라졌으면 그리기를 멈춤. */
  sync: () => void;
  /** 검증 창구 — 지금 미리보기 · 제약. */
  preview: () => DrawPreview | null;
  constraint: () => { kind: DrawConstraint; lengthM: number; slopePct: number };
  setConstraint: (kind: DrawConstraint, lengthM?: number, slopePct?: number) => void;
}

const fmt = (value: number): string => value.toFixed(1);
const signed = (value: number): string => `${value >= 0 ? "+" : ""}${value.toFixed(1)}`;
const near = (a: [number, number], b: [number, number], px: number): boolean =>
  Math.hypot(a[0] - b[0], a[1] - b[1]) <= px;

export function createPlanDraw(params: PlanDrawParams): PlanDraw {
  let mode: DrawMode = "idle";
  let editable = false;
  let active: number | null = null; // 그리는 선 차례
  let strokeStart: PlanNetwork | null = null; // Esc 로 돌아갈 꼴
  let preview: DrawPreview | null = null;
  let candidates: Vertex[] = [];
  let kind: DrawConstraint = "free";
  let lengthM = DRAW_DEFAULT_LENGTH_M;
  let slopePct = DRAW_DEFAULT_SLOPE_PCT;

  // ── 좌측 칸 ─────────────────────────────────────────────
  const mainButton = createButton({
    label: "본선 긋기",
    variant: "filled",
    size: 28,
    onClick: () => setMode(mode === "draw" && active === 0 ? "idle" : "draw"),
  });
  const branchButton = createButton({
    label: "갈래",
    variant: "ghost",
    size: 28,
    onClick: () => setMode(mode === "branch" ? "idle" : "branch"),
  });
  const markButton = createButton({
    label: "구역 마크",
    variant: "ghost",
    size: 28,
    onClick: () => setMode(mode === "mark" ? "idle" : "mark"),
  });
  const modeRow = document.createElement("div");
  modeRow.className = "d03-plan__row";
  modeRow.append(mainButton, branchButton, markButton);
  const kindSegment = createSegment({
    options: [
      { value: "free", label: "자유" },
      { value: "length", label: "길이 고정" },
      { value: "slope", label: "기울기 고정" },
      { value: "both", label: "둘 다" },
    ],
    value: kind,
    size: 24,
    ariaLabel: "긋기 제약",
    onChange: (value) => {
      kind = value as DrawConstraint;
      fieldsState();
    },
  });
  kindSegment.root.dataset.role = "draw-constraint";
  const lengthField = createInputField({
    label: "길이",
    type: "number",
    value: String(lengthM),
    min: 1,
    unit: "m",
    size: 24,
    onInput: (value) => {
      const next = Number(value);
      if (next > 0) lengthM = next;
      lengthField.setError(next > 0 ? undefined : "0 보다 큰 수");
    },
  });
  lengthField.input.dataset.role = "draw-length";
  const slopeField = createInputField({
    label: "기울기(+ 오르막)",
    type: "number",
    value: String(slopePct),
    unit: "%",
    size: 24,
    onInput: (value) => {
      const next = Number(value);
      if (value.trim() !== "" && Number.isFinite(next)) slopePct = next;
      slopeField.setError(value.trim() !== "" && Number.isFinite(next) ? undefined : "숫자");
    },
  });
  slopeField.input.dataset.role = "draw-slope";
  const fieldRow = document.createElement("div");
  fieldRow.className = "d03-plan__row";
  fieldRow.append(lengthField.root, slopeField.root);
  const hint = createText("", "muted");
  hint.classList.add("d03-plan__hint");
  const panel = document.createElement("div");
  panel.className = "d03-plan__draw";
  panel.append(modeRow, kindSegment.root, fieldRow, hint);

  function fieldsState(): void {
    lengthField.input.disabled = kind === "free" || kind === "slope";
    slopeField.input.disabled = kind === "free" || kind === "length";
  }

  function panelState(): void {
    const network = params.network();
    const done = reachedEnd(network, params.base().end);
    mainButton.querySelector(".ui-btn__label")!.textContent =
      mode === "draw" && active === 0 ? "긋기 끝" : done ? "본선 끝남" : "본선 긋기";
    mainButton.disabled = !editable || (done && !(mode === "draw" && active === 0));
    branchButton.disabled = !editable || lineLength(network.lines[0]?.vertices ?? []) <= 0;
    markButton.disabled = branchButton.disabled;
    branchButton.setAttribute("aria-pressed", String(mode === "branch"));
    markButton.setAttribute("aria-pressed", String(mode === "mark"));
    panel.dataset.mode = mode;
    hint.textContent = !editable
      ? "보기만 — 산림청 계정에서 긋습니다."
      : mode === "draw"
        ? "누름 = 점 · Enter 끝 · Esc 취소 · Backspace 마지막 점 빼기"
        : mode === "branch"
          ? "갈래를 시작할 선 위 점을 누르세요."
          : mode === "mark"
            ? "선 위를 눌러 구역을 나눕니다 · 오른쪽 누름 = 마크 지움"
            : done
              ? "본선이 종점에 닿았습니다 — 갈래 · 구역 마크 · 연도를 정하세요."
              : "[본선 긋기]로 시점에서 점을 찍어 갑니다.";
  }
  fieldsState();

  // ── 셈 ──────────────────────────────────────────────────
  const lastOf = (line: number): Vertex | null => {
    const vertices = params.network().lines[line]?.vertices ?? [];
    return vertices[vertices.length - 1] ?? null;
  };

  /** 마우스 자리 → 찍을 점 · 값 — 종점 붙기가 제약보다 먼저(본선만). */
  function previewAt(px: number, py: number, map: ScreenMap): DrawPreview | null {
    if (active === null) return null;
    const from = lastOf(active);
    if (!from) return null;
    const z = params.heightAt();
    const cursor = map.toMetric(px, py);
    const end = params.base().end;
    candidates = kind === "both" ? compassCandidates(from, lengthM, slopePct, z) : [];
    let point: Vertex | null = cursor;
    let note: string | null = null;
    let snapped = false;
    if (active === 0 && near(map.toScreen(end), [px, py], SNAP_PX)) {
      [point, note, snapped] = [end, "종점에 붙음", true];
    } else if (kind === "length") {
      point = fixedLengthPoint(from, cursor, lengthM);
    } else if (kind === "slope") {
      point = fixedSlopePoint(from, cursor, slopePct, z);
      if (!point) note = `이 방향엔 ${signed(slopePct)} % 자리 없음`;
    } else if (kind === "both") {
      point = compassPoint(from, cursor, lengthM, slopePct, z);
      if (!point) note = `반지름 ${fmt(lengthM)} m 원 위에 ${signed(slopePct)} % 자리 없음`;
    }
    const at = point ?? cursor;
    const length = segmentLength(from, at);
    return {
      point: at,
      lengthM: length,
      slopePct: groundSlopePct(from, at, z),
      note,
      blocked: !point || length <= 0,
      snapped,
    };
  }

  /** 화면 px 둘레 선 위 자리 — 가장 가까운 선 · 누가 · 꺾임점(가까우면) · 구간. */
  function lineAt(
    px: number,
    py: number,
    map: ScreenMap,
  ): { line: number; atM: number; point: Vertex; vertex: number | null; segment: number } | null {
    const cursor = map.toMetric(px, py);
    let best: ReturnType<typeof lineAt> = null;
    let bestPx = LINE_HIT_PX;
    params.network().lines.forEach((line, index) => {
      if (line.vertices.length < 2) return;
      const vertex = line.vertices.findIndex((v) => near(map.toScreen(v), [px, py], SNAP_PX));
      const atM =
        vertex >= 0
          ? lineLength(line.vertices.slice(0, vertex + 1))
          : distanceAlong(line.vertices, cursor);
      const point = vertex >= 0 ? line.vertices[vertex] : pointAtDistance(line.vertices, atM);
      const [sx, sy] = map.toScreen(point);
      const gap = vertex >= 0 ? 0 : Math.hypot(sx - px, sy - py);
      if (gap > bestPx || (best && gap === bestPx)) return;
      // 누가가 든 구간(꺾임점 끼울 자리)
      let segment = 0;
      for (let walked = 0; segment < line.vertices.length - 2; segment += 1) {
        walked += segmentLength(line.vertices[segment], line.vertices[segment + 1]);
        if (walked >= atM) break;
      }
      best = { line: index, atM, point, vertex: vertex >= 0 ? vertex : null, segment };
      bestPx = gap;
    });
    return best;
  }

  // ── 모드 ────────────────────────────────────────────────
  function stop(): void {
    // 점 하나뿐인 갈래는 버림(본선 시점은 남김)
    const network = params.network();
    if (active !== null && active > 0 && (network.lines[active]?.vertices.length ?? 0) < 2)
      params.commit(dropLastLine(network));
    active = null;
    strokeStart = null;
    preview = null;
    candidates = [];
  }

  function setMode(next: DrawMode): void {
    if (mode === "draw") stop();
    mode = editable ? next : "idle";
    if (mode === "draw") {
      const network = params.network();
      if (reachedEnd(network, params.base().end)) {
        showToast("본선이 이미 종점에 닿았습니다 — 갈래는 [갈래]로 긋습니다.", "info");
        mode = "idle";
      } else {
        active = 0;
        strokeStart = network;
      }
    }
    panelState();
    params.onMode();
  }

  function addPoint(): boolean {
    if (active === null || !preview) return false;
    if (preview.blocked) {
      showToast(preview.note ?? "여기에는 점을 찍을 수 없습니다.", "info");
      return false;
    }
    const line = active;
    const ended = preview.snapped;
    params.commit(appendVertex(params.network(), line, preview.point));
    if (ended) {
      showToast("본선이 종점에 닿았습니다.", "success");
      setMode("idle");
    }
    return true;
  }

  const layer: PlanMapLayer = {
    draw(context, map) {
      const colors = planColors();
      const { start, end } = params.base();
      const network = params.network();
      context.lineCap = "round";
      context.lineJoin = "round";
      network.lines.forEach((line, index) => {
        if (line.vertices.length < 2) return;
        context.strokeStyle = index === active ? colors.active : colors.line;
        context.lineWidth = index === 0 ? 3 : 2.5;
        context.beginPath();
        line.vertices.forEach((v, i) => {
          const [sx, sy] = map.toScreen(v);
          if (i) context.lineTo(sx, sy);
          else context.moveTo(sx, sy);
        });
        context.stroke();
        drawStationTicks(
          context,
          line.vertices.map(([x, y]) => ({ x, y })),
          {
            intervalM: PLAN_STATION_INTERVAL_M,
            pxPerMeter: map.pxPerMeter,
            toScreen: (x, y) => map.toScreen([x, y]),
            uprightRad: map.uprightRad,
            chainages: stationChainages(lineLength(line.vertices), PLAN_STATION_INTERVAL_M),
          },
        );
        segmentLabels(context, map, line.vertices);
      });
      // 꺾임점
      context.fillStyle = "#ffffff";
      for (const line of network.lines)
        for (const v of line.vertices.slice(1)) {
          const [sx, sy] = map.toScreen(v);
          context.beginPath();
          context.arc(sx, sy, 3, 0, Math.PI * 2);
          context.fill();
        }
      drawPieces(context, map, network);
      drawPreview(context, map, colors);
      // 시점(초록) · 종점(빨강)
      for (const [point, fill] of [
        [start, "#16a34a"],
        [end, "#dc2626"],
      ] as const) {
        const [sx, sy] = map.toScreen(point);
        context.beginPath();
        context.arc(sx, sy, 7, 0, Math.PI * 2);
        context.fillStyle = fill;
        context.fill();
        context.lineWidth = 2;
        context.strokeStyle = "#ffffff";
        context.stroke();
      }
    },
    press(px, py, map, button) {
      if (!editable) return false;
      if (mode === "draw" && button === 0) {
        preview = previewAt(px, py, map);
        return addPoint();
      }
      if (mode === "branch" && button === 0) {
        const hit = lineAt(px, py, map);
        if (!hit) return false;
        let network = params.network();
        let vertex = hit.vertex;
        if (vertex === null) {
          network = insertVertex(network, hit.line, hit.segment, hit.point);
          vertex = hit.segment + 1;
        }
        strokeStart = params.network();
        params.commit(addBranch(network, hit.line, vertex));
        mode = "draw";
        active = params.network().lines.length - 1;
        panelState();
        params.onMode();
        return true;
      }
      if (mode === "mark") {
        const hit = lineAt(px, py, map);
        if (!hit) return false;
        const network = params.network();
        const id = network.lines[hit.line].id;
        const next =
          button === 2
            ? removeMark(network, id, hit.atM, SNAP_PX / map.pxPerMeter)
            : splitPiece(network, id, hit.atM);
        if (next !== network) params.commit(next);
        return true;
      }
      return false;
    },
    hover(px, py, map) {
      preview = mode === "draw" ? previewAt(px, py, map) : null;
    },
    leave() {
      preview = null;
    },
  };

  function segmentLabels(
    context: CanvasRenderingContext2D,
    map: ScreenMap,
    vertices: Vertex[],
  ): void {
    const z = params.heightAt();
    for (let i = 1; i < vertices.length; i += 1) {
      const [a, b] = [map.toScreen(vertices[i - 1]), map.toScreen(vertices[i])];
      if (Math.hypot(b[0] - a[0], b[1] - a[1]) < LABEL_MIN_PX) continue;
      const slope = groundSlopePct(vertices[i - 1], vertices[i], z);
      const text = `${fmt(segmentLength(vertices[i - 1], vertices[i]))} m · ${slope === null ? "—" : `${signed(slope)} %`}`;
      label(context, map, (a[0] + b[0]) / 2, (a[1] + b[1]) / 2 - 12, text, "11px");
    }
  }

  function drawPieces(
    context: CanvasRenderingContext2D,
    map: ScreenMap,
    network: PlanNetwork,
  ): void {
    const colors = planColors();
    network.pieces.forEach((piece) => {
      const vertices = network.lines.find((line) => line.id === piece.line)?.vertices;
      if (!vertices || vertices.length < 2) return;
      if (piece.from_m > 0) {
        const [sx, sy] = map.toScreen(pointAtDistance(vertices, piece.from_m));
        context.beginPath();
        context.moveTo(sx, sy - 8);
        context.lineTo(sx + 6, sy);
        context.lineTo(sx, sy + 8);
        context.lineTo(sx - 6, sy);
        context.closePath();
        context.fillStyle = colors.active;
        context.fill();
        context.lineWidth = 1.5;
        context.strokeStyle = "#ffffff";
        context.stroke();
      }
      const [mx, my] = map.toScreen(pointAtDistance(vertices, (piece.from_m + piece.to_m) / 2));
      label(context, map, mx, my + 16, `${piece.year}년`, "bold 12px");
    });
  }

  function drawPreview(
    context: CanvasRenderingContext2D,
    map: ScreenMap,
    colors: ReturnType<typeof planColors>,
  ): void {
    if (active === null || !preview) return;
    const from = lastOf(active);
    if (!from) return;
    const [ax, ay] = map.toScreen(from);
    const [bx, by] = map.toScreen(preview.point);
    if (kind === "both") {
      context.strokeStyle = colors.active;
      context.lineWidth = 1;
      context.setLineDash([3, 4]);
      context.beginPath();
      context.arc(ax, ay, lengthM * map.pxPerMeter, 0, Math.PI * 2);
      context.stroke();
      context.fillStyle = colors.active;
      for (const c of candidates) {
        const [cx, cy] = map.toScreen(c);
        context.beginPath();
        context.arc(cx, cy, 3, 0, Math.PI * 2);
        context.fill();
      }
    }
    context.strokeStyle = preview.blocked ? colors.warn : colors.active;
    context.lineWidth = 2;
    context.setLineDash([6, 4]);
    context.beginPath();
    context.moveTo(ax, ay);
    context.lineTo(bx, by);
    context.stroke();
    context.setLineDash([]);
    context.beginPath();
    context.arc(bx, by, 5, 0, Math.PI * 2);
    context.stroke();
    const value =
      `${fmt(preview.lengthM)} m · ` +
      (preview.slopePct === null ? "지형 밖" : `${signed(preview.slopePct)} %`);
    label(
      context,
      map,
      bx + 14,
      by - 14,
      preview.note ? `${value} · ${preview.note}` : value,
      "12px",
      "left",
    );
  }

  function label(
    context: CanvasRenderingContext2D,
    map: ScreenMap,
    x: number,
    y: number,
    text: string,
    font: string,
    align: CanvasTextAlign = "center",
  ): void {
    map.upright(context, x, y, () => {
      context.font = `${font} system-ui, sans-serif`;
      context.textAlign = align;
      context.textBaseline = "middle";
      context.lineWidth = 3;
      context.strokeStyle = planColors().halo;
      context.strokeText(text, x, y);
      context.fillStyle = "#ffffff";
      context.fillText(text, x, y);
    });
  }

  panelState();

  return {
    layer,
    panel,
    mode: () => mode,
    setMode,
    setEditable(next) {
      editable = next;
      if (!editable) setMode("idle");
      panelState();
    },
    key(event) {
      if (mode === "draw" && event.key === "Enter") {
        setMode("idle");
        return true;
      }
      if (mode !== "idle" && event.key === "Escape") {
        if (mode === "draw" && strokeStart && strokeStart !== params.network())
          params.commit(strokeStart);
        active = null; // 되돌린 꼴이라 stop 의 갈래 버림은 안 함
        setMode("idle");
        return true;
      }
      if (mode === "draw" && active !== null && event.key === "Backspace") {
        const network = params.network();
        const step =
          active > 0 && network.lines[active].vertices.length < 2
            ? dropLastLine(network)
            : dropLastVertex(network, active);
        if (typeof step === "string") showToast(step, "info");
        else if (step !== network) params.commit(step);
        if (active >= params.network().lines.length) setMode("idle");
        return true;
      }
      return false;
    },
    sync() {
      if (active !== null && active >= params.network().lines.length) {
        active = null;
        mode = "idle";
      }
      panelState();
    },
    preview: () => preview,
    constraint: () => ({ kind, lengthM, slopePct }),
    setConstraint(next, length, slope) {
      kind = next;
      kindSegment.set(next);
      if (length !== undefined) [lengthM, lengthField.input.value] = [length, String(length)];
      if (slope !== undefined) [slopePct, slopeField.input.value] = [slope, String(slope)];
      fieldsState();
    },
  };
}