// ============================================================
// FENTON 2013 — preterm growth LMS for weight-for-GA. Table
// ported VERBATIM from public/js/calculators.js:1168-1183
// (15 GA weeks × 2 sexes × {L,M,S}). Parity against the vanilla
// implementation pinned by e2e/fixtures/calc-vectors.json +
// fenton.test.ts.
//
// Reference:
//   Fenton TR, Kim JH. A systematic review and meta-analysis
//   to revise the Fenton growth chart for preterm infants.
//   BMC Pediatr 2013;13:59.
// ============================================================

export type Sex = 'male' | 'female';
export interface Lms { L: number; M: number; S: number }

export interface FentonResult {
  L: number;
  M: number;
  S: number;
  z: number;
  percentile: number;
}

// Verbatim from calculators.js:1168-1183.
export const fentonLMS: Record<Sex, Record<number, Lms>> = {
  male: {
    22: { L: 0.21,  M: 496,  S: 0.17 }, 24: { L: 0.21,  M: 660,  S: 0.17 }, 26: { L: 0.21,  M: 870,  S: 0.16 },
    28: { L: 0.20,  M: 1124, S: 0.15 }, 30: { L: 0.18,  M: 1430, S: 0.14 }, 32: { L: 0.15,  M: 1795, S: 0.14 },
    34: { L: 0.12,  M: 2230, S: 0.13 }, 36: { L: 0.08,  M: 2710, S: 0.13 }, 38: { L: 0.04,  M: 3195, S: 0.12 },
    40: { L: 0.01,  M: 3530, S: 0.12 }, 42: { L: -0.02, M: 3820, S: 0.12 }, 44: { L: -0.04, M: 4200, S: 0.12 },
    46: { L: -0.06, M: 4680, S: 0.12 }, 48: { L: -0.07, M: 5200, S: 0.12 }, 50: { L: -0.08, M: 5760, S: 0.12 },
  },
  female: {
    22: { L: 0.23,  M: 474,  S: 0.17 }, 24: { L: 0.22,  M: 610,  S: 0.17 }, 26: { L: 0.22,  M: 810,  S: 0.16 },
    28: { L: 0.21,  M: 1040, S: 0.15 }, 30: { L: 0.19,  M: 1330, S: 0.14 }, 32: { L: 0.16,  M: 1680, S: 0.14 },
    34: { L: 0.12,  M: 2090, S: 0.13 }, 36: { L: 0.08,  M: 2540, S: 0.13 }, 38: { L: 0.04,  M: 3000, S: 0.12 },
    40: { L: 0.01,  M: 3340, S: 0.12 }, 42: { L: -0.02, M: 3630, S: 0.12 }, 44: { L: -0.04, M: 4010, S: 0.12 },
    46: { L: -0.06, M: 4470, S: 0.12 }, 48: { L: -0.07, M: 4970, S: 0.12 }, 50: { L: -0.08, M: 5510, S: 0.12 },
  },
};

// Verbatim from calculators.js:2299-2311.
export function interpolateLMS(table: Record<number, Lms>, val: number): Lms {
  const keys = Object.keys(table).map(Number).sort((a, b) => a - b);
  if (val <= keys[0]) return table[keys[0]];
  if (val >= keys[keys.length - 1]) return table[keys[keys.length - 1]];
  for (let i = 0; i < keys.length - 1; i++) {
    if (val >= keys[i] && val <= keys[i + 1]) {
      const t = (val - keys[i]) / (keys[i + 1] - keys[i]);
      const lms1 = table[keys[i]];
      const lms2 = table[keys[i + 1]];
      return {
        L: lms1.L + t * (lms2.L - lms1.L),
        M: lms1.M + t * (lms2.M - lms1.M),
        S: lms1.S + t * (lms2.S - lms1.S),
      };
    }
  }
  return table[keys[0]];
}

// Verbatim from calculators.js:2313-2316.
export function calcZ(value: number, L: number, M: number, S: number): number {
  if (L === 0) return Math.log(value / M) / S;
  return (Math.pow(value / M, L) - 1) / (L * S);
}

// Abramowitz & Stegun normal CDF approximation, verbatim from
// calculators.js:2318-2326.
export function zToPercentile(z: number): number {
  const t = 1 / (1 + 0.2316419 * Math.abs(z));
  const d = 0.3989423 * Math.exp(-z * z / 2);
  let p = d * t * (0.3193815 + t * (-0.3565638 + t * (1.781478 + t * (-1.821256 + t * 1.330274))));
  if (z > 0) p = 1 - p;
  return p * 100;
}

export function fentonWeightForAge(gaWeeks: number, weightGrams: number, sex: Sex): FentonResult {
  const lms = interpolateLMS(fentonLMS[sex], gaWeeks);
  const z = calcZ(weightGrams, lms.L, lms.M, lms.S);
  const percentile = zToPercentile(z);
  return { L: lms.L, M: lms.M, S: lms.S, z, percentile };
}

// Clinical classification — per AAP 2017 / Fenton 2013:
//   SGA: <10th percentile, LGA: >90th, AGA: between.
export type SizeForAge = 'SGA' | 'AGA' | 'LGA';
export function classifySizeForAge(percentile: number): SizeForAge {
  if (percentile < 10) return 'SGA';
  if (percentile > 90) return 'LGA';
  return 'AGA';
}

// ============================================================
// Fenton 2013 — peditools-derived higher-accuracy table used by
// the Bedside Neonatal module. Ported VERBATIM from
// public/js/bedside/neonatal.js:20-37. Comment from that file:
//   "LMS parameters derived empirically from peditools.org/
//    fenton2013 — peditools is widely used and consistent with
//    the published Fenton TR, Kim JH. BMC Pediatrics 2013;13:59
//    reference. Each week's triple was fit against 6 probe weights
//    per week (RMSE < 0.005 z-score units). Replaces an earlier
//    hand-rounded table whose z-scores drifted ~0.05 SD from
//    peditools/Epic near term."
//
// This table is 21 GA weeks (22-42) in 1-week steps, more granular
// than the coarser 15-week version in fentonLMS above. Use
// fentonLMS for the Calculators / Growth Charts pill (matches the
// vanilla calc output). Use fentonLmsPeditools for the Bedside
// Neonatal sub-module (matches peditools.org z-scores to 3 decimal
// places and is what Daniel uses clinically).
// ============================================================
export const fentonLmsPeditools: Record<Sex, Record<number, Lms>> = {
  male: {
    22: { L: 0.5885, M: 496,  S: 0.12802 }, 23: { L: 0.7565, M: 571,  S: 0.14547 },
    24: { L: 0.9128, M: 651,  S: 0.16235 }, 25: { L: 1.0544, M: 741,  S: 0.17765 },
    26: { L: 1.1862, M: 841,  S: 0.19029 }, 27: { L: 1.3051, M: 953,  S: 0.19989 },
    28: { L: 1.3699, M: 1079, S: 0.20777 }, 29: { L: 1.4165, M: 1223, S: 0.21163 },
    30: { L: 1.4172, M: 1388, S: 0.21185 }, 31: { L: 1.3755, M: 1578, S: 0.20785 },
    32: { L: 1.2952, M: 1790, S: 0.20112 }, 33: { L: 1.1974, M: 2018, S: 0.19143 },
    34: { L: 1.0743, M: 2255, S: 0.18119 }, 35: { L: 0.9583, M: 2493, S: 0.16992 },
    36: { L: 0.8460, M: 2726, S: 0.16001 }, 37: { L: 0.7543, M: 2947, S: 0.15072 },
    38: { L: 0.6650, M: 3156, S: 0.14304 }, 39: { L: 0.5881, M: 3360, S: 0.13641 },
    40: { L: 0.5237, M: 3568, S: 0.13173 }, 41: { L: 0.4691, M: 3785, S: 0.12863 },
    42: { L: 0.4216, M: 4014, S: 0.12735 },
  },
  female: {
    22: { L: -0.0868, M: 481,  S: 0.13605 }, 23: { L: 0.2119, M: 537,  S: 0.14635 },
    24: { L: 0.5281,  M: 606,  S: 0.16134 }, 25: { L: 0.8258, M: 694,  S: 0.18077 },
    26: { L: 1.0501,  M: 792,  S: 0.19889 }, 27: { L: 1.2084, M: 899,  S: 0.21323 },
    28: { L: 1.2599,  M: 1017, S: 0.22437 }, 29: { L: 1.2539, M: 1152, S: 0.22982 },
    30: { L: 1.2262,  M: 1306, S: 0.23082 }, 31: { L: 1.1223, M: 1482, S: 0.22733 },
    32: { L: 1.0122,  M: 1681, S: 0.21846 }, 33: { L: 0.8746, M: 1897, S: 0.20681 },
    34: { L: 0.7299,  M: 2126, S: 0.19407 }, 35: { L: 0.5929, M: 2362, S: 0.18059 },
    36: { L: 0.4534,  M: 2602, S: 0.17028 }, 37: { L: 0.3462, M: 2835, S: 0.16139 },
    38: { L: 0.2636,  M: 3050, S: 0.15513 }, 39: { L: 0.2069, M: 3239, S: 0.15004 },
    40: { L: 0.1670,  M: 3415, S: 0.14649 }, 41: { L: 0.1517, M: 3596, S: 0.14359 },
    42: { L: 0.1308,  M: 3787, S: 0.14127 },
  },
};

// Neonatal-specific Z — uses |L|<0.001 threshold instead of L===0
// to handle the interpolated near-zero L values cleanly.
// Verbatim from public/js/bedside/neonatal.js:53-56.
export function calcZNeonatal(value: number, L: number, M: number, S: number): number {
  if (Math.abs(L) < 0.001) return Math.log(value / M) / S;
  return (Math.pow(value / M, L) - 1) / (L * S);
}

// Abramowitz & Stegun normal CDF (Erf form), verbatim from
// public/js/bedside/neonatal.js:58-66. This is a different
// approximation from zToPercentile above (which uses the Pythagoras
// polynomial form) — same asymptotic answer, different rounding.
// Kept as a separate function so the Neonatal numbers match the
// vanilla Bedside output exactly.
export function zToPercentileNeonatal(z: number): number {
  const a1 = 0.254829592, a2 = -0.284496736, a3 = 1.421413741;
  const a4 = -1.453152027, a5 = 1.061405429, p = 0.3275911;
  const sign = z < 0 ? -1 : 1;
  const x = Math.abs(z) / Math.sqrt(2);
  const t = 1 / (1 + p * x);
  const y = 1 - (((((a5 * t + a4) * t) + a3) * t + a2) * t + a1) * t * Math.exp(-x * x);
  return Math.round(((1 + sign * y) / 2) * 1000) / 10;
}

export interface NeonatalGaClass { label: string; color: string; icon: string }
export interface NeonatalBwClass { label: string; color: string }
export interface NeonatalWeightClass { label: string; color: string; detail: string }

export function classifyGA(weeks: number, days = 0): NeonatalGaClass {
  const total = weeks + days / 7;
  if (total < 28) return { label: 'Extremely Preterm',  color: '#dc2626', icon: 'triangle-exclamation' };
  if (total < 32) return { label: 'Very Preterm',        color: '#ea580c', icon: 'triangle-exclamation' };
  if (total < 34) return { label: 'Moderate Preterm',   color: '#d97706', icon: 'circle-exclamation' };
  if (total < 37) return { label: 'Late Preterm',        color: '#ca8a04', icon: 'circle-info' };
  if (total < 39) return { label: 'Early Term',          color: '#2563eb', icon: 'circle-info' };
  if (total < 41) return { label: 'Full Term',           color: '#16a34a', icon: 'circle-check' };
  if (total < 42) return { label: 'Late Term',           color: '#d97706', icon: 'circle-info' };
  return              { label: 'Post Term',              color: '#dc2626', icon: 'triangle-exclamation' };
}

export function classifyBirthWeight(grams: number): NeonatalBwClass {
  if (grams < 1000)  return { label: 'Extremely Low Birth Weight (ELBW)', color: '#dc2626' };
  if (grams < 1500)  return { label: 'Very Low Birth Weight (VLBW)',      color: '#ea580c' };
  if (grams < 2500)  return { label: 'Low Birth Weight (LBW)',            color: '#d97706' };
  if (grams <= 4000) return { label: 'Normal Birth Weight',                color: '#16a34a' };
  return              { label: 'Macrosomia (>4000g)',                      color: '#ea580c' };
}

export function classifyWeightPercentile(percentile: number): NeonatalWeightClass {
  if (percentile < 3)  return { label: 'Severely SGA', color: '#dc2626', detail: '<3rd percentile' };
  if (percentile < 10) return { label: 'SGA',          color: '#ea580c', detail: '<10th percentile' };
  if (percentile > 97) return { label: 'Severely LGA', color: '#dc2626', detail: '>97th percentile' };
  if (percentile > 90) return { label: 'LGA',          color: '#ea580c', detail: '>90th percentile' };
  return                { label: 'AGA',                 color: '#16a34a', detail: '10th-90th percentile' };
}

// Main neonatal assessment using the peditools-accurate Fenton table.
export interface NeonatalAssessment {
  gaDecimal: number;
  gaClass: NeonatalGaClass;
  bwClass: NeonatalBwClass;
  weightClass: NeonatalWeightClass;
  expectedWeight: number;
  z: number;
  percentile: number;
  L: number; M: number; S: number;
}
export function neonatalAssess(weeks: number, days: number, weightGrams: number, sex: Sex): NeonatalAssessment {
  const gaDecimal = weeks + days / 7;
  const lms = interpolateLMS(fentonLmsPeditools[sex], gaDecimal);
  const z = calcZNeonatal(weightGrams, lms.L, lms.M, lms.S);
  const percentile = zToPercentileNeonatal(z);
  return {
    gaDecimal,
    gaClass: classifyGA(weeks, days),
    bwClass: classifyBirthWeight(weightGrams),
    weightClass: classifyWeightPercentile(percentile),
    expectedWeight: Math.round(lms.M),
    z,
    percentile,
    L: lms.L, M: lms.M, S: lms.S,
  };
}