// Parser for oxy conflict markers (spec §9.5). No vscode imports, so it is

// tested with plain Node.

//

//   <<<<<<< oxy conflict 1 of 2, side 1 of 2: change k7m2p9 "Add retry loop"

//   ...

//   ======= oxy conflict 1 of 2, side 2 of 2: change q3x8w1 "Refactor client"

//   ...

//   >>>>>>> oxy conflict 1 of 2 end

//

// A delete/insert conflict's first side reads `deleted by change X` and is

// followed by a `-------` line and the deleted context.

export interface ConflictSide {

  /** 1-based side number. */

  number: number;

  /** `k7m2p9 "Add retry loop"` or `deleted by change k7m2p9`. */

  label: string;

  deleted: boolean;

  /** Line index of the side's header. */

  header: number;

  /** Content lines (exclusive end). */

  start: number;

  end: number;

}

export interface ConflictRegion {

  number: number;

  total: number;

  /** Line index of `<<<<<<<`. */

  start: number;

  /** Line index of `>>>>>>>`. */

  end: number;

  sides: ConflictSide[];

}

const OPEN = /^<<<<<<< oxy conflict (\d+) of (\d+), side (\d+) of (\d+): (.*)$/;

const NEXT = /^======= oxy conflict (\d+) of (\d+), side (\d+) of (\d+): (.*)$/;

const CLOSE = /^>>>>>>> oxy conflict (\d+) of (\d+) end$/;

export function parseConflicts(lines: string[]): ConflictRegion[] {

  const regions: ConflictRegion[] = [];

  let current: ConflictRegion | undefined;

  let side: ConflictSide | undefined;

  for (let i = 0; i < lines.length; i++) {

    const line = lines[i];

    const open = OPEN.exec(line);

    if (open && !current) {

      current = { number: Number(open[1]), total: Number(open[2]), start: i, end: -1, sides: [] };

      side = newSide(Number(open[3]), open[5], i);

      if (side.deleted && lines[i + 1] === "-------") {

        side.start = i + 2;

        i += 1;

      }

      current.sides.push(side);

      continue;

    }

    const next = current ? NEXT.exec(line) : null;

    if (next && current && side) {

      side.end = i;

      side = newSide(Number(next[3]), next[5], i);

      current.sides.push(side);

      continue;

    }

    const close = current ? CLOSE.exec(line) : null;

    if (close && current && side) {

      side.end = i;

      current.end = i;

      regions.push(current);

      current = undefined;

      side = undefined;

    }

  }

  return regions;

}

function newSide(number: number, label: string, header: number): ConflictSide {

  const deleted = label.startsWith("deleted by change ");

  return { number, label: deleted ? label : label.replace(/^change /, ""), deleted, header, start: header + 1, end: header + 1 };

}

/** The lines that replace a region when `keep` (side numbers) are kept, in order. */

export function resolveRegion(lines: string[], region: ConflictRegion, keep: number[]): string[] {

  const out: string[] = [];

  for (const n of keep) {

    const side = region.sides.find((s) => s.number === n);

    if (!side || side.deleted) {

      continue;

    }

    out.push(...lines.slice(side.start, side.end));

  }

  return out;

}

/** A conflict candidate file's real name, or undefined. */

export function candidateBase(path: string): string | undefined {

  const m = /^(.*)\.oxy-conflict-\d+$/.exec(path);

  return m ? m[1] : undefined;

}