// SpellGrid on the command line: `npx tsx src/cli.ts levels/l1-double-tap.json`.
//
// A thin loop over the harness: it draws the level, reads a command, and calls
// `step`, `cast` or `play`. No rules live here.
//
//   w a s d          one turn: up, left, down, right
//   c <card> [x y]   cast a spell from your hand (at the minion on (x, y), if given),
//                    or play a minion from your hand onto the empty tile (x, y)
//   q                quit
//
// Assemble's choices (Graft) are asked for one at a time: answer with a number or a name.

import { readFileSync, readSync } from "node:fs";
import { pathToFileURL } from "node:url";
import { newSpellGrid, type LevelDef, type SpellGrid } from "./harness";

const DIRS = { w: "up", a: "left", s: "down", d: "right" } as const;

/** One cell of the drawing: the newest object on the tile, as 3 letters; TEXT in capitals. */
function cell(g: SpellGrid, x: number, y: number): string {
  const kinds = g.kindsAt(x, y);
  if (kinds.length === 0) return " . ";
  // kindsAt is sorted; prefer text, which is what the player reads.
  const kind = kinds.find((k) => k.startsWith("text:")) ?? kinds[0];
  const name = kind.startsWith("text:") ? kind.slice(5).toUpperCase() : kind.toLowerCase();
  return name.slice(0, 3).padEnd(3);
}

/** The level as text: the grid, the rules, the minions and the hand. */
export function render(g: SpellGrid, level: LevelDef): string {
  const lines: string[] = [];
  for (let y = 0; y < level.height; y++) {
    const row: string[] = [];
    for (let x = 0; x < level.width; x++) row.push(cell(g, x, y));
    lines.push(row.join(" "));
  }
  lines.push(`Rules: ${g.activeRules().join(", ")}`);
  const minions: string[] = [];
  for (let y = 0; y < level.height; y++) {
    for (let x = 0; x < level.width; x++) {
      const id = g.minionAt(x, y);
      if (id !== null) minions.push(`${g.nameOf(id)} (${x},${y}) ${g.health(id)} Health`);
    }
  }
  lines.push(`Minions: ${minions.join("; ") || "none"}`);
  lines.push(`Hand: ${g.hand().join(", ") || "empty"}`);
  return lines.join("\n");
}

/** A `c` command: `c <card words...> [x y]`. */
function parseCast(args: string[]): { card: string; at?: [number, number] } {
  const n = args.length;
  if (n >= 3 && /^\d+$/.test(args[n - 2]) && /^\d+$/.test(args[n - 1])) {
    return { card: args.slice(0, n - 2).join(" "), at: [Number(args[n - 2]), Number(args[n - 1])] };
  }
  return { card: args.join(" ") };
}

/**
 * Play `levelText` (a level in the course's format), reading commands from
 * `readLine` (undefined at the end of input) and writing to `write`. Returns
 * `"won"`, `"lost"` or `"quit"`.
 */
export function run(levelText: string, readLine: () => string | undefined, write: (s: string) => void): string {
  const level = JSON.parse(levelText) as LevelDef;
  const g = newSpellGrid(level, []);
  g.setChooser((kind, options) => {
    write(`Choose the ${kind} (a number or a name):\n${options.map((o, i) => `  ${i + 1}) ${o}`).join("\n")}\n? `);
    const answer = readLine()?.trim() ?? "";
    return options.includes(answer) ? answer : (options[Number(answer) - 1] ?? options[0]);
  });
  for (;;) {
    write(`${render(g, level)}\n`);
    if (g.won()) {
      write("You win!\n");
      return "won";
    }
    if (g.lost()) {
      write("Nothing is YOU. You lose.\n");
      return "lost";
    }
    write("> ");
    const line = readLine();
    if (line === undefined) return "quit";
    const [command, ...args] = line.trim().split(/\s+/);
    try {
      if (command === "q") return "quit";
      if (command in DIRS) g.step(DIRS[command as keyof typeof DIRS]);
      else if (command === "c" && args.length > 0) {
        const { card, at } = parseCast(args);
        const target = at === undefined ? null : g.minionAt(...at);
        if (at === undefined) g.cast(card);
        else if (target !== null) g.cast(card, target);
        else g.play(card, ...at);
      } else write("Commands: w a s d (move), c <card> [x y] (cast or play), q (quit)\n");
    } catch (e) {
      write(`${e instanceof Error ? e.message : String(e)}\n`);
    }
  }
}

/** Lines from standard input, read synchronously, so the chooser can ask mid-Sequence. */
function stdinLines(): () => string | undefined {
  const buffer = Buffer.alloc(4096);
  let pending = "";
  let ended = false;
  return () => {
    while (!pending.includes("\n") && !ended) {
      const n = readSync(0, buffer, 0, buffer.length, null);
      if (n === 0) ended = true;
      else pending += buffer.toString("utf8", 0, n);
    }
    if (pending === "" && ended) return undefined;
    const end = pending.indexOf("\n");
    const line = end < 0 ? pending : pending.slice(0, end);
    pending = end < 0 ? "" : pending.slice(end + 1);
    return line;
  };
}

if (process.argv[1] !== undefined && import.meta.url === pathToFileURL(process.argv[1]).href) {
  const path = process.argv[2];
  if (path === undefined) {
    process.stderr.write("usage: npx tsx src/cli.ts <level.json>\n");
    process.exit(2);
  }
  const outcome = run(readFileSync(path, "utf8"), stdinLines(), (s) => process.stdout.write(s));
  process.exit(outcome === "won" ? 0 : 1);
}