// Makespan — Scoring block.
//
// The canonical objective: minimize the latest finish day. Shipping it as a
// block (rather than every caller hand-writing the two-line scorer) gives
// the makespan a registry name a run config can reference and weight.
//
// MiniZinc compile contract: harness supplies `finish_day[t]` and `TASKS`.

import { z } from "zod";

import type { Schedule, Scorer } from "../level-core/types.ts";

import type { MiniZincFragment, ScoringBlock } from "./types.ts";

export const MakespanInputSchema = z.object({});

export type MakespanInput = z.infer<typeof MakespanInputSchema>;

const ScorerOutputSchema: z.ZodType<Scorer> = z.custom<Scorer>(
  (val): val is Scorer =>
    typeof val === "object" &&
    val !== null &&
    typeof (val as Scorer).name === "string" &&
    ((val as Scorer).direction === "min" ||
      (val as Scorer).direction === "max") &&
    typeof (val as Scorer).score === "function",
);

export const MakespanBlock: ScoringBlock<MakespanInput> = {
  id: "Makespan",
  schema: { input: MakespanInputSchema, output: ScorerOutputSchema },
  apply: (): Scorer => ({
    name: "Makespan",
    direction: "min",
    score: (schedule: Schedule): number => schedule.makespan,
  }),
  toMiniZinc: (): MiniZincFragment => ({
    text: `var int: makespan = max(t in TASKS) (finish_day[t]);`,
  }),
  doc: {
    nl: "The latest finish day across all tasks — the schedule's total length.",
    pseudocode: "max(finish(task) for task in tasks)",
  },
};