import type { PierModel } from '../geometry';
import { INTEGRATED_BLOCK, type IntegratedBlock } from '../integrated-block';

/**
 * 받침블럭 철근 (spec §6.3 · plan C2), 배치 분리: one block per bearing, 1200 × 1200.
 * The settings come from the input (승인 2026-10-26): S1 and S2 have their own spacing (따로 입력), the side cover c_s
 * and the first-bar gap e_s are shared, and the S1 depth is the top cover + half of S1 + half of S2 (피복 + S1/2 + S2/2).
 * S2 is the upper bar (depth = top cover); S1 is the lower bar.
 */
export interface BlockRebarSettings {
  /** 상면 피복 (철근 중심까지, mm). */
  coverTop: number;
  /** 측면 피복 (S1 다리·S2 끝, mm). */
  coverSide: number;
  /** 첫 철근 최소 여유 (측면 피복 다음, mm). */
  firstGap: number;
  /** 간격 S1 (mm). */
  spacingS1: number;
  /** 간격 S2 (mm). */
  spacingS2: number;
  /** 다리 길이 (철근 중심에서 아래로, mm). */
  legLength: number;
}

/** Defaults: the P1 values of 받침블럭철근.md (피복 50 · 여유 75 · @125 · 다리 700). */
export const DEFAULT_BLOCK_REBAR: BlockRebarSettings = {
  coverTop: 50,
  coverSide: 50,
  firstGap: 75,
  spacingS1: 125,
  spacingS2: 125,
  legLength: 700,
};

/** H19 bar diameter (mm) of both S1 and S2. */
const H19 = 19.1;

/** Depth of each bar centre below the block top (mm): S2 = top cover; S1 = top cover + S1/2 + S2/2. */
export function barDepths(s: BlockRebarSettings): { S1: number; S2: number } {
  return { S2: s.coverTop, S1: s.coverTop + H19 / 2 + H19 / 2 };
}

export interface BarRow {
  name: 'S1' | 'S2';
  /** Bars along one block side. */
  count: number;
  spacing: number;
  /** Position of the first bar from the block edge. */
  firstEnd: number;
  /** Straight length plus two legs (mm). */
  length: number;
  /** Coping embedment of the legs (mm): legLength − (block height − bar depth). */
  embedment: number;
}

/** Bars along one side: available = dim − 2·(cover + first gap); gaps = floor(available / spacing). */
export function barsAcross(
  dim: number = 1200,
  spacing: number = DEFAULT_BLOCK_REBAR.spacingS2,
  s: BlockRebarSettings = DEFAULT_BLOCK_REBAR,
): { count: number; spacing: number; firstEnd: number } {
  const available = dim - 2 * (s.coverSide + s.firstGap);
  const gaps = Math.floor(available / spacing);
  const span = gaps * spacing;
  const leftover = available - span;
  return { count: gaps + 1, spacing, firstEnd: s.coverSide + s.firstGap + leftover / 2 };
}

/** Length of one bar (mm): the straight part a − 2·c_s plus two legs (2500 for the 1200 block with the defaults). */
export function barLength(dim: number = 1200, s: BlockRebarSettings = DEFAULT_BLOCK_REBAR): number {
  return dim - 2 * s.coverSide + 2 * s.legLength;
}

/** Rebar of one block; blockHeight is the bearing block height in mm (block top − bottom, pad excluded). */
export function blockBars(blockHeight: number, dim: number = 1200, s: BlockRebarSettings = DEFAULT_BLOCK_REBAR): BarRow[] {
  const depth = barDepths(s);
  const length = barLength(dim, s);
  return [
    { name: 'S1', ...barsAcross(dim, s.spacingS1, s), length, embedment: s.legLength - (blockHeight - depth.S1) },
    { name: 'S2', ...barsAcross(dim, s.spacingS2, s), length, embedment: s.legLength - (blockHeight - depth.S2) },
  ];
}

export interface BlockRebar {
  no: number;
  row: '전열' | '후열';
  bars: BarRow[];
}

/**
 * Rebar of one 일체 block (승인 2026-10-26, 받침블럭철근.md "일체 a 2500"): S2 runs along the 교각축 (1200) with the bars
 * across the 2500 length (10 on the front half, 9 on the back half); its legs are measured from the top of the half it sits in.
 * S1 runs along the 2500 length, across the 1200 depth; its depth is taken from the lower top.
 */
export function integratedBlockBars(ib: IntegratedBlock, s: BlockRebarSettings = DEFAULT_BLOCK_REBAR): BarRow[] {
  const half = INTEGRATED_BLOCK.length / 2;
  const depth = barDepths(s);
  const s2 = barsAcross(INTEGRATED_BLOCK.length, s.spacingS2, s);
  const frontCount = Array.from({ length: s2.count }, (_, k) => s2.firstEnd + k * s2.spacing).filter((x) => x <= half + 1e-9).length;
  const backCount = s2.count - frontCount;
  const hFront = (ib.topFront - ib.bottom) * 1000;
  const hBack = (ib.topBack - ib.bottom) * 1000;
  const legS2 = (h: number) => s.legLength - (h - depth.S2);
  const s1 = barsAcross(INTEGRATED_BLOCK.depth, s.spacingS1, s);
  const hLow = Math.min(hFront, hBack);
  const rows: BarRow[] = [
    { name: 'S2', count: frontCount, spacing: s2.spacing, firstEnd: s2.firstEnd, length: barLength(INTEGRATED_BLOCK.depth, s), embedment: legS2(hFront) },
  ];
  if (backCount > 0) rows.push({ name: 'S2', count: backCount, spacing: s2.spacing, firstEnd: s2.firstEnd, length: barLength(INTEGRATED_BLOCK.depth, s), embedment: legS2(hBack) });
  rows.push({ name: 'S1', count: s1.count, spacing: s1.spacing, firstEnd: s1.firstEnd, length: barLength(INTEGRATED_BLOCK.length, s), embedment: s.legLength - (hLow - depth.S1) });
  return rows;
}

/**
 * Rebar of every block of a pier. The block height is the model's own block (coping top → block top, pad excluded),
 * since the bar depths are measured from the block top. The settings come from the model (input).
 */
export function bearingBlockRebar(model: PierModel): BlockRebar[] {
  const s = model.blockRebar;
  // 일체 (승인 2026-10-26): one block per pair replaces the two per-bearing blocks.
  if (model.integratedBlocks.length > 0) {
    return model.integratedBlocks.map((ib) => ({ no: ib.frontNo, row: '전열', bars: integratedBlockBars(ib, s) }));
  }
  return model.blocks.map((b) => ({
    no: b.no,
    row: b.row,
    bars: blockBars((b.top - b.bottom) * 1000, 1200, s),
  }));
}

/** Total bars of one pier: bars per block × blocks, for S1 and S2 separately. */
export function totals(rebar: BlockRebar[]): { S1: number; S2: number } {
  return rebar.reduce(
    (sum, blk) => {
      for (const bar of blk.bars) sum[bar.name] += bar.count;
      return sum;
    },
    { S1: 0, S2: 0 },
  );
}