code-advent-2025/src/exercises/day_7.ts

type TachyonManifold = string[][];

export default async function Laboratories() {
  const tachyon_manifold = await read_tachyon_manifold(
    "src/exercises/assets/day_7_input.txt",
  );
  console.log(">> Bean splits: ", count_bean_splits(tachyon_manifold));
  const total_splits = count_quantum_splits(tachyon_manifold);
  console.log(">> Cuantum splits: ", total_splits);
}

export function count_bean_splits(tm: TachyonManifold): number {
  let split_count = 0;

  tm.forEach((row, y) => {
    row.forEach((point, x) => {
      switch (point) {
        case ".": {
          const prev_point = tm[y - 1]?.[x];
          if (prev_point === "S" || prev_point === "|") {
            tm[y][x] = "|";
          }
          break;
        }
        case "^": {
          const prev_point = tm[y - 1][x];
          if (prev_point === "|") {
            split_count += 1;
            const left_point = tm[y][x - 1];
            if (left_point === ".") {
              tm[y][x - 1] = "|";
            }
            const right_point = tm[y][x + 1];
            if (right_point === ".") {
              tm[y][x + 1] = "|";
            }
          }
          break;
        }
      }
    });
  });

  return split_count;
}

export function count_quantum_splits(tm: TachyonManifold): number {
  const full_tree = generate_full_quantum_tree(tm);

  // Downwards
  const init = full_tree[0].findIndex((p) => p === "S");
  return count_quantum_paths_downwards(full_tree, init, 1);

  // Upwards
  // let total = 0;
  // for (let i = 0; i < tm[0].length; i++) {
  //   if (tm[tm.length - 2][i] === "|") {
  //     total += count_quantum_paths_upwards(full_tree, i, tm.length - 2) + 1;
  //   }
  // }
  // return total;
}

function count_quantum_paths_downwards(
  tm: TachyonManifold,
  initial_x: number,
  initial_y: number,
): number {
  let total = 0;
  const FILE_END = tm.length - 2;
  const current = tm[initial_y][initial_x];

  if (initial_y > FILE_END) {
    return 0;
  }
  if (initial_y === FILE_END && current === "|") {
    return 1;
  } else if (initial_y === FILE_END) {
    return 0;
  }

  const next = tm[initial_y + 1][initial_x];
  switch (next) {
    case "|": {
      total += count_quantum_paths_downwards(tm, initial_x, initial_y + 1);
      break;
    }
    case "^": {
      total += count_quantum_paths_downwards(tm, initial_x - 1, initial_y + 1);
      total += count_quantum_paths_downwards(tm, initial_x + 1, initial_y + 1);
      break;
    }
  }

  return total;
}

export function count_quantum_paths_upwards(
  tm: TachyonManifold,
  initial_x: number,
  initial_y: number,
): number {
  if (initial_y === 0) {
    return 0;
  }

  let total = 0;

  let current_bean = tm[initial_y][initial_x];
  while (current_bean !== "." && initial_y > 2) {
    switch (current_bean) {
      case "|": {
        const left_point = tm[initial_y][initial_x - 1];
        const right_point = tm[initial_y][initial_y + 1];
        // WRONG: the splitter existing does not mean that it has a bean
        if (left_point === "^" && right_point === "^") {
          total += 1;
        }
        if (left_point === "^") {
          total += count_quantum_paths_upwards(
            tm,
            initial_x - 1,
            initial_y - 1,
          );
        }
        if (right_point === "^") {
          total += count_quantum_paths_upwards(
            tm,
            initial_x + 1,
            initial_y - 1,
          );
        }

        if (left_point === "^" || right_point === "^") {
          const contiues_upwards = tm[initial_y - 1][initial_x] === "|";
          if (contiues_upwards) {
            total += 1;
          }
        }
      }
    }
    initial_y--;
    current_bean = tm[initial_y][initial_x];
  }
  return total;
}

export function generate_full_quantum_tree(
  tm: TachyonManifold,
): TachyonManifold {
  tm.forEach((row, y) => {
    row.forEach((point, x) => {
      switch (point) {
        case ".": {
          const prev_point = tm[y - 1]?.[x];
          if (prev_point === "S" || prev_point === "|") {
            tm[y][x] = "|";
          }
          break;
        }
        case "^": {
          const prev_point = tm[y - 1][x];
          if (prev_point === "|") {
            const left_point = tm[y][x - 1];
            if (left_point === ".") {
              tm[y][x - 1] = "|";
            }
            const right_point = tm[y][x + 1];
            if (right_point === ".") {
              tm[y][x + 1] = "|";
            }
          }
          break;
        }
      }
    });
  });

  return tm;
}

/*
 * @deprecated since its to inefficient
 */
function generate_quantum_split(
  tachyonManifold: TachyonManifold,
): TachyonManifold[] {
  const tm = tachyonManifold.map((a) => a.slice());

  const quantum_tms: TachyonManifold[] = [];

  tm.forEach((row, y) => {
    row.forEach((point, x) => {
      switch (point) {
        case ".": {
          const prev_point = tm[y - 1]?.[x];
          if (prev_point === "S" || prev_point === "|") {
            tm[y][x] = "|";
          }
          break;
        }
        case "^": {
          const prev_point = tm[y - 1][x];
          if (prev_point === "|") {
            const left_point = tm[y][x - 1];
            if (left_point === ".") {
              const left_tm = tm.map((a) => a.slice());
              left_tm[y][x - 1] = "|";
              quantum_tms.push(...generate_quantum_split(left_tm));
            }
            // Right
            const right_point = tm[y][x + 1];
            if (right_point === ".") {
              const right_tm = tm.map((a) => a.slice());
              tm[y][x + 1] = "|";
              quantum_tms.push(...generate_quantum_split(right_tm));
            }
          }
          break;
        }
        case "S":
          break;
      }
    });
  });

  return quantum_tms;
}

export async function read_tachyon_manifold(
  path: string,
): Promise<TachyonManifold> {
  const input_txt = await Deno.readTextFile(path);
  const input_rows = input_txt.split("\n");
  return input_rows.map((row) => {
    return row.split("");
  });
}