import { register } from "./registry";
import { makeErrorCell } from "../error";
import type { Value } from "../types";

const num = (v: unknown): number | null => v == null ? null : Number(v);

register({
  name: "round", arity: { min: 1, max: 2 }, paramTypes: ["number", "number"], returnType: "number",
  eval: ([v, places]) => {
    const n = num(v);
    if (n == null) return null;
    const p = places == null ? 0 : Math.trunc(Number(places));
    const factor = Math.pow(10, p);
    return Math.round(n * factor) / factor;
  },
  doc: "Rounds to the nearest integer, or to `places` decimals if given.", category: "math",
});
register({
  name: "floor", arity: { min: 1, max: 1 }, paramTypes: ["number"], returnType: "number",
  eval: ([v]) => { const n = num(v); return n == null ? null : Math.floor(n); },
  doc: "Rounds down.", category: "math",
});
register({
  name: "ceil", arity: { min: 1, max: 1 }, paramTypes: ["number"], returnType: "number",
  eval: ([v]) => { const n = num(v); return n == null ? null : Math.ceil(n); },
  doc: "Rounds up.", category: "math",
});
register({
  name: "abs", arity: { min: 1, max: 1 }, paramTypes: ["number"], returnType: "number",
  eval: ([v]) => { const n = num(v); return n == null ? null : Math.abs(n); },
  doc: "Absolute value.", category: "math",
});
register({
  name: "min", arity: { min: 1, max: null }, paramTypes: "variadic-any", returnType: "number",
  eval: (args) => {
    const nums = args.map(num).filter((n): n is number => n != null);
    return nums.length ? Math.min(...nums) : null;
  },
  doc: "Minimum of the arguments.", category: "math",
});
register({
  name: "max", arity: { min: 1, max: null }, paramTypes: "variadic-any", returnType: "number",
  eval: (args) => {
    const nums = args.map(num).filter((n): n is number => n != null);
    return nums.length ? Math.max(...nums) : null;
  },
  doc: "Maximum of the arguments.", category: "math",
});
register({
  name: "mod", arity: { min: 2, max: 2 }, paramTypes: ["number", "number"], returnType: "number",
  eval: ([a, b]) => {
    const na = num(a), nb = num(b);
    if (na == null || nb == null) return null;
    if (nb === 0) return makeErrorCell("DIV_BY_ZERO", "modulo by zero");
    return na % nb;
  },
  doc: "Remainder after division.", category: "math",
});
register({
  name: "add", arity: { min: 2, max: 2 }, paramTypes: ["number", "number"], returnType: "number",
  eval: ([a, b]) => {
    const na = num(a), nb = num(b);
    return na == null || nb == null ? null : na + nb;
  },
  doc: "Sum of two numbers.", category: "math",
});
register({
  name: "subtract", arity: { min: 2, max: 2 }, paramTypes: ["number", "number"], returnType: "number",
  eval: ([a, b]) => {
    const na = num(a), nb = num(b);
    return na == null || nb == null ? null : na - nb;
  },
  doc: "Difference of two numbers.", category: "math",
});
register({
  name: "multiply", arity: { min: 2, max: 2 }, paramTypes: ["number", "number"], returnType: "number",
  eval: ([a, b]) => {
    const na = num(a), nb = num(b);
    return na == null || nb == null ? null : na * nb;
  },
  doc: "Product of two numbers.", category: "math",
});
register({
  name: "divide", arity: { min: 2, max: 2 }, paramTypes: ["number", "number"], returnType: "number",
  eval: ([a, b]) => {
    const na = num(a), nb = num(b);
    if (na == null || nb == null) return null;
    if (nb === 0) return makeErrorCell("DIV_BY_ZERO", "division by zero");
    return na / nb;
  },
  doc: "Quotient of two numbers.", category: "math",
});
register({
  name: "pow", arity: { min: 2, max: 2 }, paramTypes: ["number", "number"], returnType: "number",
  eval: ([a, b]) => {
    const na = num(a), nb = num(b);
    return na == null || nb == null ? null : Math.pow(na, nb);
  },
  doc: "Base raised to an exponent.", category: "math",
});
register({
  name: "sqrt", arity: { min: 1, max: 1 }, paramTypes: ["number"], returnType: "number",
  eval: ([v]) => {
    const n = num(v);
    if (n == null) return null;
    if (n < 0) return makeErrorCell("TYPE_MISMATCH", "sqrt of negative number");
    return Math.sqrt(n);
  },
  doc: "Positive square root.", category: "math",
});
register({
  name: "sum", arity: { min: 1, max: null }, paramTypes: "variadic-any", returnType: "number",
  eval: (args) => {
    // Null propagates as 0 so `sum(prop("A"), prop("B"))` still works when
    // some cells are empty — matches Airtable/Notion semantics.
    let total = 0;
    for (const v of args) {
      const n = num(v);
      if (n != null && Number.isFinite(n)) total += n;
    }
    return total;
  },
  doc: "Sum of the arguments.", category: "math",
});
const meanEval = (args: Value[]): Value => {
  const nums: number[] = [];
  for (const v of args) {
    const n = num(v);
    if (n != null && Number.isFinite(n)) nums.push(n);
  }
  if (nums.length === 0) return null;
  return nums.reduce((a, b) => a + b, 0) / nums.length;
};
register({
  name: "mean", arity: { min: 1, max: null }, paramTypes: "variadic-any", returnType: "number",
  eval: meanEval,
  doc: "Arithmetic average of the arguments.", category: "math",
});
register({
  name: "average", arity: { min: 1, max: null }, paramTypes: "variadic-any", returnType: "number",
  eval: meanEval,
  doc: "Arithmetic average of the arguments (alias of mean).", category: "math",
});
register({
  name: "median", arity: { min: 1, max: null }, paramTypes: "variadic-any", returnType: "number",
  eval: (args) => {
    const nums: number[] = [];
    for (const v of args) {
      const n = num(v);
      if (n != null && Number.isFinite(n)) nums.push(n);
    }
    if (nums.length === 0) return null;
    nums.sort((a, b) => a - b);
    const mid = Math.floor(nums.length / 2);
    return nums.length % 2 === 0
      ? (nums[mid - 1] + nums[mid]) / 2
      : nums[mid];
  },
  doc: "Middle value of the arguments.", category: "math",
});