import type { Classification, TaskKind } from "./types.js";

interface Rule {
  kind: TaskKind;
  score: number;
  pattern: RegExp;
  reason: string;
}

const rules: readonly Rule[] = [
  { kind: "architecture", score: 78, pattern: /\b(architect(?:ure|ural)?|redesign|security audit|system design|migration plan|(?:database|data|schema) migrat(?:e|ion))\b/i, reason: "architecture evidence" },
  { kind: "debugging", score: 70, pattern: /\b(debug across|race condition|multi[- ]file debug|trace .* root cause|deadlock)\b/i, reason: "complex debugging evidence" },
  { kind: "research", score: 65, pattern: /\b(compare|research|investigate|find out|external behavior|dependency api)\b/i, reason: "research evidence" },
  { kind: "refactor", score: 58, pattern: /\b(refactor|reorganize|extract (?:the )?\w+|cleanup)\b/i, reason: "refactor evidence" },
  { kind: "bugfix", score: 35, pattern: /\b(fix|bug|regression|broken|failing|error)\b/i, reason: "bug-fix evidence" },
  { kind: "explanation", score: 18, pattern: /\b(explain|what does|how does|documentation|where is)\b/i, reason: "explanation evidence" },
  { kind: "simple", score: 10, pattern: /\b(rename|typo|format|whitespace|lint)\b/i, reason: "simple task keyword" },
  { kind: "feature", score: 48, pattern: /\b(add|implement|create|update|test)\b/i, reason: "feature evidence" },
];

const risks: readonly [RegExp, string, number][] = [
  [/\b(security|auth(?:entication|orization)?|credential)\b/i, "security", 12],
  [/\b(data loss|delete(?: all)? data|backup)\b/i, "data loss", 12],
  [/\b(migrat(?:e|ion)|production|prod)\b/i, "production or migration", 6],
  [/\b(concurren(?:cy|t)|race condition|deadlock)\b/i, "concurrency", 12],
];

export function classify(prompt: string): Classification {
  const isExplanation = /\b(explain|what does|how does|where is)\b/i.test(prompt);
  const isSimple = /\b(rename|typo|format|whitespace|lint)\b/i.test(prompt);
  const candidates = isExplanation
    ? rules.filter((rule) => rule.kind === "explanation")
    : isSimple
      ? rules.filter((rule) => rule.kind === "simple")
      : rules;
  const matched = candidates.find((rule) => rule.pattern.test(prompt));
  const kind = matched?.kind ?? "feature";
  let score = matched?.score ?? 48;
  const reasons = [matched?.reason ?? "default feature routing"];

  for (const [pattern, reason, weight] of risks) {
    if (pattern.test(prompt)) {
      score += weight;
      reasons.push(`risk: ${reason}`);
    }
  }

  return { kind, score: Math.min(score, 95), reasons };
}