import { SectionKey, SECTIONS } from "@/lib/sections";

/**
 * Keep scoring independent from question-module export shape to avoid build breaks.
 * We only rely on fields actually used for scoring.
 */
type SelectedQuestion = {
  baseId: string;
  section: SectionKey;
  type: "likert" | "mcq" | "text";
  prompt: string;
  reverse?: boolean;
  mcqScores?: Record<string, number>;
};

export type CandidateMeta = {
  candidateName: string;
  passportNumber: string; // renamed from candidateId
  jobTitle: string;
};

export type AnswerMap = Record<string, string>; // baseId -> selected option / text

export type SectionScore = {
  rawPct: number;   // 0..100
  weighted: number; // 0..100
  flags: string[];
};

export type ExamScore = {
  sections: Record<SectionKey, SectionScore>;
  overall: number; // 0..100 weighted
  decision: "Strong Hire" | "Hire" | "Proceed with Conditions" | "Do Not Proceed";
  validity: {
    completionPct: number;
    attentionFlags: number;
    inconsistentFlags: number;
  };
};

const LIKERT_MAP: Record<string, number> = {
  "Strongly Disagree": 1,
  "Disagree": 2,
  "Neutral": 3,
  "Agree": 4,
  "Strongly Agree": 5
};

function clamp(n: number, a: number, b: number) { return Math.max(a, Math.min(b, n)); }
function avg(xs: number[]) { return xs.length ? xs.reduce((s, x) => s + x, 0) / xs.length : 0; }

function scoreItemLikert(ans: string, reverse?: boolean): number | null {
  if (!ans) return null;
  const v = LIKERT_MAP[ans];
  if (!v) return null;
  const vv = reverse ? (6 - v) : v; // reverse score
  const pct = ((vv - 1) / 4) * 100; // 1..5 -> 0..100
  return clamp(pct, 0, 100);
}

function scoreItemMCQ(ans: string, mcqScores?: Record<string, number>): number | null {
  if (!ans || !mcqScores) return null;
  const raw = mcqScores[ans];
  if (typeof raw !== "number") return null;
  return clamp((raw / 5) * 100, 0, 100);
}

export function scoreExam(selected: SelectedQuestion[], answers: AnswerMap): ExamScore {
  const sections: Record<SectionKey, SectionScore> = {
    A: { rawPct: 0, weighted: 0, flags: [] },
    B: { rawPct: 0, weighted: 0, flags: [] },
    C: { rawPct: 0, weighted: 0, flags: [] },
    D: { rawPct: 0, weighted: 0, flags: [] },
    E: { rawPct: 0, weighted: 0, flags: [] },
    F: { rawPct: 0, weighted: 0, flags: [] }
  };

  const perSectionScores: Record<SectionKey, number[]> = { A: [], B: [], C: [], D: [], E: [], F: [] };
  let answered = 0;

  // validity checks
  let attentionFlags = 0;
  let inconsistentFlags = 0;

  // simple inconsistency: reverse items answered "high" too often
  let reverseHighCount = 0;
  let reverseCount = 0;

  for (const q of selected) {
    const a = (answers[q.baseId] ?? "").trim();
    if (a) answered++;

    let s: number | null = null;
    if (q.type === "likert") s = scoreItemLikert(a, q.reverse);
    if (q.type === "mcq") s = scoreItemMCQ(a, q.mcqScores);
    // text items are scored by AI separately (not included directly here)

    if (s !== null) perSectionScores[q.section].push(s);

    // attention check: detect prompt contains "attention check"
    if (q.section === "A" && q.prompt.toLowerCase().includes("attention check")) {
      // correct is Agree
      if (a && a !== "Agree") attentionFlags++;
    }

    if (q.reverse) {
      reverseCount++;
      const v = LIKERT_MAP[a] ?? 0;
      if (v >= 4) reverseHighCount++;
    }
  }

  if (reverseCount >= 10) {
    const ratio = reverseHighCount / reverseCount;
    if (ratio > 0.6) inconsistentFlags++;
  }

  for (const sec of Object.keys(sections) as SectionKey[]) {
    const raw = Math.round(avg(perSectionScores[sec]));
    const def = SECTIONS.find(s => s.key === sec)!;
    const weighted = Math.round(raw * def.weight);
    const flags: string[] = [];

    if (sec === "B" && raw < 60) flags.push("Capability threshold not met (<60).");
    if (sec === "F" && raw < 60) flags.push("Functional readiness threshold not met (<60).");
    if (raw < 50) flags.push("Section score below 50.");

    sections[sec] = { rawPct: isFinite(raw) ? raw : 0, weighted, flags };
  }

  const overall = Math.round(Object.values(sections).reduce((s, x) => s + x.weighted, 0));

  let decision: ExamScore["decision"] = "Do Not Proceed";
  const failCritical = sections.B.rawPct < 60 || sections.F.rawPct < 60;

  if (overall >= 80 && !failCritical) decision = "Strong Hire";
  else if (overall >= 70 && overall <= 79 && !failCritical) decision = "Hire";
  else if (overall >= 60 && overall <= 69 && !failCritical) decision = "Proceed with Conditions";
  else decision = "Do Not Proceed";

  if (overall < 50 || failCritical) decision = "Do Not Proceed";

  const completionPct = Math.round((answered / selected.length) * 100);

  return {
    sections,
    overall,
    decision,
    validity: { completionPct, attentionFlags, inconsistentFlags }
  };
}