import type { PierInput, Row } from './types';

/** Dimensions in m. Sources: intent.PR sheet (P1 rules) and spec.md §3 defaults. */
export const DIM = {
  columnDiameter: 2.0,
  copingH1: 1.0,
  copingH2: 1.5,
  levelWidth: 2.1,
  /** Multi-column coping: underside between columns sits this far below Level, with 45° haunches of the same size (spec §4.5, Q3 추천안). */
  haunch: 0.3,
  padThickness: 0.05,
  padSize: 1.0,
  blockSize: 1.2,
  footingL: 10.4,
  footingW: 8.15,
  footingH: 2.0,
  blindingMargin: 0.2,
  blindingT: 0.1,
  /** 강관 609.6 × 12 (spec §4.5 강관 type, Q5 추천안 적용). */
  pileDiameter: 0.6096,
  pileEnd: 0.7,
  pileSpacing: 2.25,
  /** Front/back EL difference below this is treated as no lateral step (spec §4.3, Q2). */
  lateralTolerance: 0.005,
} as const;

export interface Vec2 {
  e: number;
  n: number;
}

export interface Segment {
  s0: number;
  s1: number;
  top: number;
}

export interface BearingLocal {
  no: number;
  row: Row;
  s: number;
  n: number;
  z: number;
}

export interface BlockModel {
  no: number;
  row: Row;
  s: number;
  n: number;
  bottom: number;
  top: number;
  padTop: number;
}

export interface ColumnModel {
  s: number;
  top: number;
  bottom: number;
  diameter: number;
}

export interface FootingModel {
  s: number;
  top: number;
  bottom: number;
  length: number;
  width: number;
}

export interface BlindingModel {
  s: number;
  top: number;
  length: number;
  width: number;
  thickness: number;
}

export interface PileModel {
  s: number;
  n: number;
  top: number;
  bottom: number;
  diameter: number;
}

export interface PierModel {
  name: string;
  lengthIp: number;
  azimuthDeg: number;
  /** Unit vector along the pier axis (east, north). */
  u: Vec2;
  /** Unit vector across the axis: (u.n, -u.e). Front row is negative, back row positive. */
  nrm: Vec2;
  ip1: Vec2;
  ip2Input: Vec2;
  ip2Calc: Vec2;
  dIp2: number;
  bp1: Vec2;
  bp2: Vec2;
  /** Horizontal centre of the drawing frame: the centre of the first column. */
  pivot: Vec2;
  copingL: number;
  copingB: number;
  copingRefTop: number;
  h1: number;
  h2: number;
  segments: Segment[];
  /** Coping elevation outline as (s, EL) points, closed. */
  profile: [number, number][];
  levelBottom: number;
  endBottom: number;
  bearings: BearingLocal[];
  blocks: BlockModel[];
  columns: ColumnModel[];
  footings: FootingModel[];
  blindings: BlindingModel[];
  piles: PileModel[];
  groundEl: number;
  derived: {
    columnHeight: number;
    soilCover: number;
    pileCount: number;
    pileLayout: string | null;
    pileTipEl: number | null;
    blockHeightFront: number;
    blockHeightBack: number;
    frontBackDiffSpread: number;
  };
}

function toLocal(p: Vec2, origin: Vec2, u: Vec2, nrm: Vec2): { s: number; n: number } {
  const dx = p.e - origin.e;
  const dy = p.n - origin.n;
  return { s: dx * u.e + dy * u.n, n: dx * nrm.e + dy * nrm.n };
}

/**
 * Builds the first-stage (shape only) model of a T-type pier from one input record.
 * Pure function: same input always gives the same output. Throws for cases not implemented yet.
 */
export function buildPier(input: PierInput): PierModel {
  const ip = (name: string) => {
    const p = input.ips.find((q) => q.name === name);
    if (!p) throw new Error(`IP 누락: ${name}`);
    return p;
  };
  const ip1 = ip('IP1');
  const ip2 = ip('IP2');
  const ip3 = ip('IP3');
  const ip4 = ip('IP4');
  if (ip4.angleDeg !== 0) {
    throw new Error('미실시: 꺾인 코핑(IP4 꺾임각 ≠ 0)은 아직 지원하지 않습니다.');
  }

  const dx = ip3.x - ip1.x;
  const dy = ip3.y - ip1.y;
  const lengthIp = Math.hypot(dx, dy);
  const u: Vec2 = { e: dx / lengthIp, n: dy / lengthIp };
  const nrm: Vec2 = { e: u.n, n: -u.e };
  const azimuthDeg = (((Math.atan2(u.e, u.n) * 180) / Math.PI) + 360) % 360;

  // IP2 is a reference point at a 1:9 division of IP1–IP3 (intent.PR, spec §2.2).
  const ip2Calc: Vec2 = { e: ip1.x + 0.1 * dx, n: ip1.y + 0.1 * dy };
  const ip2Input: Vec2 = { e: ip2.x, n: ip2.y };

  const L = input.copingLengthMm / 1000;
  const B = input.copingWidthMm / 1000;
  const ip1v: Vec2 = { e: ip1.x, n: ip1.y };
  const bp1: Vec2 = { e: ip1v.e + u.e * (lengthIp / 2 - L / 2), n: ip1v.n + u.n * (lengthIp / 2 - L / 2) };
  const bp2: Vec2 = { e: bp1.e + u.e * L, n: bp1.n + u.n * L };

  const front = input.bearings.filter((b) => b.row === '전열').sort((a, b) => a.no - b.no);
  const back = input.bearings.filter((b) => b.row === '후열').sort((a, b) => a.no - b.no);
  if (front.length !== back.length) throw new Error('E02: 전열·후열 받침 수가 다릅니다.');
  if (front.length < 2) throw new Error('받침이 2개 미만입니다.');

  // Bearing block heights (spec §4.3 h1OshoeBlock / h2, pad 50 included). Not the coping end heights (DIM.copingH1/H2).
  const h1 = front[0].z - input.copingTopEl;
  const h2 = h1 + (back[0].z - front[0].z);

  const frontLocal = front.map((b) => ({ no: b.no, row: '전열' as Row, z: b.z, ...toLocal({ e: b.x, n: b.y }, bp1, u, nrm) }));
  const backLocal = back.map((b) => ({ no: b.no, row: '후열' as Row, z: b.z, ...toLocal({ e: b.x, n: b.y }, bp1, u, nrm) }));

  // Step boundaries sit midway between consecutive front bearings (spec §4.3).
  const bounds = [0];
  for (let k = 0; k < frontLocal.length - 1; k++) {
    bounds.push((frontLocal[k].s + frontLocal[k + 1].s) / 2);
  }
  bounds.push(L);
  const segments: Segment[] = frontLocal.map((b, k) => ({ s0: bounds[k], s1: bounds[k + 1], top: b.z - h1 }));

  // Lateral step: front and back coping tops must match segment by segment (not supported yet).
  frontLocal.forEach((f, k) => {
    const backTop = backLocal[k].z - h2;
    if (Math.abs(segments[k].top - backTop) > DIM.lateralTolerance) {
      throw new Error('미실시: 횡방향 단차(전열·후열 상면 차 ≥ 5 mm)는 아직 지원하지 않습니다.');
    }
  });

  // Columns (spec §4.5). Multi-column positions are placed; haunch and separate-footing checks are not.
  const colS = columnPositions(input.type, L);
  // Coping underside: ends at (top − end height h1 = 1000), Level zone at (top − h1 − h2 taper height = 1500).
  const levelBottom = input.copingTopEl - DIM.copingH1 - DIM.copingH2;
  const endBottom = input.copingTopEl - DIM.copingH1;
  const levelStart = Math.min(...colS) - DIM.levelWidth / 2;
  const levelEnd = Math.max(...colS) + DIM.levelWidth / 2;
  if (levelStart < 0 || levelEnd > L) throw new Error('코핑 길이가 Level 구간보다 짧습니다.');

  // Underside from the right end to the left end. Between columns (2·3주형) it drops 300 below Level with 300 × 300 haunches (spec §4.5, Q3).
  const underside: [number, number][] = [[L, endBottom]];
  const levelZones = [...colS].sort((a, b) => b - a).map((s) => [s - DIM.levelWidth / 2, s + DIM.levelWidth / 2] as const);
  levelZones.forEach(([zoneStart, zoneEnd], k) => {
    underside.push([zoneEnd, levelBottom], [zoneStart, levelBottom]);
    const next = levelZones[k + 1];
    if (!next) return;
    const gap = zoneStart - next[1];
    if (gap <= 2 * DIM.haunch) throw new Error('기둥 사이 간격이 헌치(300 × 2)보다 좁아 코핑 하면을 만들 수 없습니다.');
    const lowerEl = levelBottom - DIM.haunch;
    underside.push([zoneStart - DIM.haunch, lowerEl], [next[1] + DIM.haunch, lowerEl], [next[1], levelBottom]);
  });

  const profile: [number, number][] = [[0, endBottom]];
  for (const seg of segments) {
    profile.push([seg.s0, seg.top], [seg.s1, seg.top]);
  }
  profile.push(...underside);

  const footingTop = input.foundationType === '현장타설말뚝' ? input.footingBottomEl : input.footingBottomEl + DIM.footingH;
  const columns: ColumnModel[] = colS.map((s) => ({
    s,
    top: levelBottom,
    bottom: footingTop,
    diameter: DIM.columnDiameter,
  }));

  const footings: FootingModel[] = [];
  const blindings: BlindingModel[] = [];
  const piles: PileModel[] = [];
  const pileLength = input.pileLengthMm / 1000;
  const pileTip = input.footingBottomEl - pileLength;

  for (const s of colS) {
    if (input.foundationType === '현장타설말뚝') {
      piles.push({ s, n: 0, top: input.footingBottomEl, bottom: pileTip, diameter: DIM.columnDiameter });
      continue;
    }
    footings.push({ s, top: footingTop, bottom: input.footingBottomEl, length: DIM.footingL, width: DIM.footingW });
    blindings.push({
      s,
      top: input.footingBottomEl,
      length: DIM.footingL + DIM.blindingMargin,
      width: DIM.footingW + DIM.blindingMargin,
      thickness: DIM.blindingT,
    });
    if (input.foundationType === '말뚝기초') {
      piles.push(...pilesFor(s, input.footingBottomEl, pileLength));
    }
  }

  const blocks: BlockModel[] = [];
  frontLocal.forEach((b) => {
    const bottom = segmentTop(segments, b.s);
    blocks.push({ no: b.no, row: '전열', s: b.s, n: b.n, bottom, top: b.z - DIM.padThickness, padTop: b.z });
  });
  backLocal.forEach((b) => {
    const bottom = b.z - h2;
    blocks.push({ no: b.no, row: '후열', s: b.s, n: b.n, bottom, top: b.z - DIM.padThickness, padTop: b.z });
  });

  const blockHeightFront = blocks.find((b) => b.row === '전열')!.top - blocks.find((b) => b.row === '전열')!.bottom;
  const blockHeightBack = blocks.find((b) => b.row === '후열')!.top - blocks.find((b) => b.row === '후열')!.bottom;
  const diffs = frontLocal.map((f, k) => f.z - backLocal[k].z);
  const frontBackDiffSpread = Math.max(...diffs) - Math.min(...diffs);

  return {
    name: input.name,
    lengthIp,
    azimuthDeg,
    u,
    nrm,
    ip1: ip1v,
    ip2Input,
    ip2Calc,
    dIp2: (ip2Calc.e - bp1.e) * u.e + (ip2Calc.n - bp1.n) * u.n,
    bp1,
    bp2,
    pivot: { e: bp1.e + u.e * (L / 2), n: bp1.n + u.n * (L / 2) },
    copingL: L,
    copingB: B,
    copingRefTop: input.copingTopEl,
    h1,
    h2,
    segments,
    profile,
    levelBottom,
    endBottom,
    bearings: [...frontLocal, ...backLocal].map((b) => ({ no: b.no, row: b.row, s: b.s, n: b.n, z: b.z })),
    blocks,
    columns,
    footings,
    blindings,
    piles,
    groundEl: input.groundEl,
    derived: {
      columnHeight: levelBottom - columns[0].bottom,
      soilCover: input.groundEl - (input.foundationType === '현장타설말뚝' ? input.footingBottomEl : footingTop),
      pileCount: piles.length,
      pileLayout: input.foundationType === '말뚝기초' ? pileLayoutText() : null,
      pileTipEl: piles.length ? pileTip : null,
      blockHeightFront,
      blockHeightBack,
      frontBackDiffSpread,
    },
  };
}

export function columnPositions(type: PierInput['type'], L: number): number[] {
  if (type === 'T형') return [L / 2];
  if (type === '2주형') return [L / 5, L - L / 5];
  return [L / 5, L / 2, L - L / 5];
}

function segmentTop(segments: Segment[], s: number): number {
  const hit = segments.find((seg) => s >= seg.s0 && s < seg.s1) ?? segments[segments.length - 1];
  return hit.top;
}

/**
 * Piles under one footing (spec §4.6): rows across the footing width, piles along the length,
 * both with an end distance of 0.7 m and an even spacing that never exceeds 2.25 m.
 */
export function pileGrid(): { countS: number; countN: number; spacingS: number; spacingN: number } {
  const span = (size: number) => Math.floor((size - 2 * DIM.pileEnd) / DIM.pileSpacing) + 1;
  const countS = span(DIM.footingL);
  const countN = span(DIM.footingW);
  return {
    countS,
    countN,
    spacingS: (DIM.footingL - 2 * DIM.pileEnd) / (countS - 1),
    spacingN: (DIM.footingW - 2 * DIM.pileEnd) / (countN - 1),
  };
}

/** Display string such as "4@2250 × 3@2250 = 20본" (gaps along the length × gaps across the width). */
export function pileLayoutText(): string {
  const g = pileGrid();
  return `${g.countS - 1}@${Math.round(g.spacingS * 1000)} × ${g.countN - 1}@${Math.round(g.spacingN * 1000)} = ${g.countS * g.countN}본`;
}

export function pilesFor(s: number, topEl: number, length: number): PileModel[] {
  const { countS, countN, spacingS, spacingN } = pileGrid();
  const out: PileModel[] = [];
  for (let i = 0; i < countS; i++) {
    for (let j = 0; j < countN; j++) {
      out.push({
        s: s + (i - (countS - 1) / 2) * spacingS,
        n: (j - (countN - 1) / 2) * spacingN,
        top: topEl,
        bottom: topEl - length,
        diameter: DIM.pileDiameter,
      });
    }
  }
  return out;
}