import type { CommandMode, ParsedCommand, WorkPackage } from "./work-package-types";

export type CommandParseResult = {
  parsed: ParsedCommand;
  matchedWorkPackageId?: string;
  matchedWorkPackageTitle?: string;
  suggestions?: { id: string; title: string; shortName: string }[];
  error?: string;
};

const MODES: CommandMode[] = ["ask", "plan", "change", "execute"];

function normalize(s: string): string {
  return s.trim().replace(/\s+/g, " ").toLowerCase();
}

function matchWorkPackageByName(
  workPackages: WorkPackage[],
  name: string,
): { id: string; title: string; shortName: string } | undefined {
  const n = normalize(name);
  if (!n) return;
  return workPackages.find((wp) => {
    return normalize(wp.title) === n || normalize(wp.shortName) === n;
  });
}

function getSuggestions(workPackages: WorkPackage[], name: string) {
  const n = normalize(name);
  if (!n) return [];

  // Cheap “contains” suggestion without pulling in a fuzzy-match dep.
  return workPackages
    .map((wp) => ({
      id: wp.id,
      title: wp.title,
      shortName: wp.shortName,
      score:
        Number(normalize(wp.title).includes(n)) +
        Number(normalize(wp.shortName).includes(n)),
    }))
    .filter((x) => x.score > 0)
    .sort((a, b) => b.score - a.score)
    .slice(0, 5)
    .map(({ id, title, shortName }) => ({ id, title, shortName }));
}

export function parseCommand(
  text: string,
  workPackages: WorkPackage[],
): CommandParseResult {
  const raw = text.trim();
  if (!raw.startsWith("@")) {
    return { parsed: { instruction: raw } };
  }

  const afterAt = raw.slice(1).trim();
  if (!afterAt) {
    return { parsed: { instruction: "" }, error: "Missing work package name." };
  }

  const tokens = afterAt.split(/\s+/g);

  // Find explicit mode token (if present).
  let modeIdx = -1;
  for (let i = 0; i < tokens.length; i++) {
    if (MODES.includes(tokens[i].toLowerCase() as CommandMode)) {
      modeIdx = i;
      break;
    }
  }

  // If mode is missing, infer the longest package-name prefix that matches.
  if (modeIdx === -1) {
    let bestMatchLen = 0;
    let bestMatch:
      | { id: string; title: string; shortName: string; matchedName: string }
      | undefined;
    for (let len = Math.min(tokens.length, 10); len >= 1; len--) {
      const candidate = tokens.slice(0, len).join(" ");
      const m = matchWorkPackageByName(workPackages, candidate);
      if (m) {
        bestMatchLen = len;
        bestMatch = { ...m, matchedName: candidate };
        break;
      }
    }

    if (!bestMatch) {
      const guessName = tokens[0];
      return {
        parsed: { referencedPackageName: guessName, mode: "ask", instruction: tokens.slice(1).join(" ") },
        suggestions: getSuggestions(workPackages, guessName),
        error: `Work package not found: "${guessName}".`,
      };
    }

    const instruction = tokens.slice(bestMatchLen).join(" ").trim();
    return {
      parsed: {
        referencedPackageName: bestMatch.matchedName,
        mode: "ask",
        instruction,
      },
      matchedWorkPackageId: bestMatch.id,
      matchedWorkPackageTitle: bestMatch.title,
    };
  }

  const packageName = tokens.slice(0, modeIdx).join(" ").trim();
  const mode = tokens[modeIdx].toLowerCase() as CommandMode;
  const instruction = tokens.slice(modeIdx + 1).join(" ").trim();

  const m = matchWorkPackageByName(workPackages, packageName);
  if (!m) {
    return {
      parsed: { referencedPackageName: packageName, mode, instruction },
      suggestions: getSuggestions(workPackages, packageName),
      error: `Work package not found: "${packageName}".`,
    };
  }

  return {
    parsed: { referencedPackageName: m.title, mode, instruction },
    matchedWorkPackageId: m.id,
    matchedWorkPackageTitle: m.title,
  };
}