/* =============================================================================
 * E07_StabArea_Raster.ts
 * E07 광역 위험 지도 화면 계산(PLAN 536-2) — 저장본 격자 풀기 · 등급 · 안전율 색 · RGBA · 셀 찾기.
 *   격자 꼴 = 서버 `E07_StabArea_Router.py` 머리 주석(fs · si uint16 ×1000 · cls uint8 · slope ×10 ·
 *   m ×100 · 작은 끝 base64 · 행 0 = 남쪽). 순수 함수만(DOM · fetch 금지).
 * ========================================================================== */

export interface Grid {
  x0: number;
  y0: number;
  dx: number;
  nx: number;
  ny: number;
}

export type LevelKey = "low" | "mid" | "high";

export interface StationRow {
  chainage_m: number;
  label: string | null;
  cells: number;
  fs_min?: number;
  si_min?: number;
  worst_class?: number;
  risk_area_m2?: number;
  risk_ratio?: number;
  level?: LevelKey;
  slope_max_deg?: number;
}

export interface AreaSummary {
  areas_m2: Record<string, number>;
  band_area_m2: number;
  covered_area_m2: number;
  risk_area_m2: number;
  fs_min: number | null;
  station_levels: Record<LevelKey, number>;
  stations: number;
}

export interface AreaResult {
  stale?: boolean;
  computed_at: string;
  elapsed_s: number;
  settings: Record<string, unknown>;
  grid: Grid;
  fs: string;
  si: string;
  cls: string;
  slope: string;
  m: string;
  stations: StationRow[];
  summary: AreaSummary;
}

/** 풀어 둔 격자 — 자료 없음 = NaN(fs · si · slope · m) · 0(cls) */
export interface Decoded {
  grid: Grid;
  fs: Float32Array;
  si: Float32Array;
  cls: Uint8Array;
  slope: Float32Array;
  m: Float32Array;
}

/** 등급 열쇠(서버 CLASS_KEYS 차례 · 1~6) */
export const CLASS_KEYS = ["stable", "moderate", "quasi", "lower", "upper", "defended"] as const;
export const RISK_CLASS = 4;
/** 측점 등급(서버 LEVEL_KEYS 차례) · 색 */
export const LEVEL_KEYS: readonly LevelKey[] = ["low", "mid", "high"];
export const LEVEL_COLORS: Record<LevelKey, string> = {
  low: "#1a9850",
  mid: "#fee08b",
  high: "#d73027",
};

/** 등급 색 1~6 — SINMAP 관례(초록 → 빨강) */
export const CLASS_COLORS = ["#1a9850", "#91cf60", "#d9ef8b", "#fee08b", "#fc8d59", "#d73027"];

/** 안전율 색 단계 — 1.0 · 1.2 · 1.5 경계 */
export const FS_STEPS: readonly { below: number; color: string }[] = [
  { below: 1.0, color: "#a50026" },
  { below: 1.2, color: "#f46d43" },
  { below: 1.5, color: "#fee08b" },
  { below: 2.0, color: "#a6d96a" },
  { below: Infinity, color: "#1a9850" },
];

function bytes(text: string): Uint8Array {
  const raw = atob(text);
  const out = new Uint8Array(raw.length);
  for (let i = 0; i < raw.length; i += 1) out[i] = raw.charCodeAt(i);
  return out;
}

function u16(text: string, scale: number): Float32Array {
  const b = bytes(text);
  const view = new DataView(b.buffer);
  const out = new Float32Array(b.length / 2);
  for (let i = 0; i < out.length; i += 1) {
    const v = view.getUint16(i * 2, true);
    out[i] = v === 65535 ? NaN : v / scale;
  }
  return out;
}

export function decode(result: AreaResult): Decoded {
  const m = bytes(result.m);
  return {
    grid: result.grid,
    fs: u16(result.fs, 1000),
    si: u16(result.si, 1000),
    cls: bytes(result.cls),
    slope: u16(result.slope, 10),
    m: Float32Array.from(m, (v) => (v === 255 ? NaN : v / 100)),
  };
}

function rgb(hex: string): [number, number, number] {
  const n = Number.parseInt(hex.slice(1), 16);
  return [(n >> 16) & 255, (n >> 8) & 255, n & 255];
}

export function fsColor(value: number): string {
  return (FS_STEPS.find((s) => value < s.below) ?? FS_STEPS[FS_STEPS.length - 1]).color;
}

/** 격자 → RGBA(줄 0 = 북쪽 끝 · 캔버스 그림용) · 자료 없음 = 투명 */
export function rasterRgba(data: Decoded, layer: "cls" | "fs"): Uint8ClampedArray<ArrayBuffer> {
  const { nx, ny } = data.grid;
  const out = new Uint8ClampedArray(nx * ny * 4);
  const classRgb = CLASS_COLORS.map(rgb);
  const fsRgb = FS_STEPS.map((s) => rgb(s.color));
  for (let iy = 0; iy < ny; iy += 1) {
    const row = ny - 1 - iy;
    for (let ix = 0; ix < nx; ix += 1) {
      const i = iy * nx + ix;
      const k = data.cls[i];
      if (!k) continue;
      const j = FS_STEPS.findIndex((s) => data.fs[i] < s.below);
      const color = layer === "cls" ? classRgb[k - 1] : fsRgb[j < 0 ? fsRgb.length - 1 : j];
      const at = (row * nx + ix) * 4;
      out[at] = color[0];
      out[at + 1] = color[1];
      out[at + 2] = color[2];
      out[at + 3] = 255;
    }
  }
  return out;
}

/** 모델 좌표 → 셀 번호(격자 밖 = -1) */
export function cellIndex(grid: Grid, x: number, y: number): number {
  const ix = Math.round((x - grid.x0) / grid.dx);
  const iy = Math.round((y - grid.y0) / grid.dx);
  return ix < 0 || iy < 0 || ix >= grid.nx || iy >= grid.ny ? -1 : iy * grid.nx + ix;
}

/** 등급별 셀 수(1~6) — 범례 · 검증용 */
export function classCounts(data: Decoded): number[] {
  const out = [0, 0, 0, 0, 0, 0];
  for (const k of data.cls) if (k) out[k - 1] += 1;
  return out;
}