// Maîtrise estimée par concept : score composite [0,1] mis à jour par lissage exponentiel,
// dont le pas dépend de la force de l'évidence (type de tâche, difficulté, autonomie, confiance).
// Présenté partout comme une ESTIMATION. Voir docs/learning-science-strategy.md.

import { all, get, run } from "../db/index.ts";

export type MasteryLevel = "a-decouvrir" | "en-construction" | "solide" | "maitrise";

export function levelFor(score: number): MasteryLevel {
  if (score >= 0.85) return "maitrise";
  if (score >= 0.6) return "solide";
  if (score >= 0.3) return "en-construction";
  return "a-decouvrir";
}

export const LEVEL_LABELS: Record<MasteryLevel, string> = {
  "a-decouvrir": "À découvrir",
  "en-construction": "En construction",
  solide: "Solide",
  maitrise: "Maîtrisé",
};

const KIND_WEIGHT: Record<string, number> = { exam: 1.0, quiz: 0.75, correction: 0.7, flashcard: 0.45 };

export function recordMasteryEvent(opts: {
  userId: number;
  conceptId: number;
  kind: "flashcard" | "quiz" | "exam" | "correction";
  correct: boolean;
  difficulty?: number; // 1-5
  autonomy?: number;   // 1 sans aide ; 0.5 avec indices
  confidence?: number; // 1-5 déclaré
}) {
  const difficulty = Math.min(5, Math.max(1, opts.difficulty ?? 3));
  const autonomy = Math.min(1, Math.max(0.2, opts.autonomy ?? 1));
  run(
    "INSERT INTO mastery_events (user_id, concept_id, kind, correct, difficulty, autonomy, confidence) VALUES (?, ?, ?, ?, ?, ?, ?)",
    opts.userId, opts.conceptId, opts.kind, opts.correct ? 1 : 0, difficulty, autonomy, opts.confidence ?? null
  );

  const row = get<{ score: number; observations: number }>(
    "SELECT score, observations FROM mastery WHERE user_id = ? AND concept_id = ?",
    opts.userId, opts.conceptId
  );
  const prior = row?.score ?? 0.15;
  const observations = (row?.observations ?? 0) + 1;

  // Force de l'évidence : tâche exigeante réussie sans aide = signal fort.
  const kindW = KIND_WEIGHT[opts.kind] ?? 0.5;
  const diffW = 0.6 + difficulty * 0.13; // 0.73 → 1.25
  let evidence = kindW * diffW * autonomy;

  // Cible de l'observation : réussite → vers le haut (plus haut si difficile),
  // échec → vers le bas (plus bas si l'item était facile).
  const target = opts.correct ? Math.min(1, 0.7 + difficulty * 0.06) : Math.max(0, 0.35 - (5 - difficulty) * 0.06);

  // Calibration de la confiance : sur-confiance erronée légèrement pénalisée.
  if (opts.confidence != null) {
    const conf = (opts.confidence - 1) / 4;
    if (opts.correct && Math.abs(conf - 1) < 0.3) evidence *= 1.05;
    if (!opts.correct && conf > 0.7) evidence *= 1.15;
  }

  const alpha = Math.min(0.5, 0.12 + evidence * 0.22); // pas d'apprentissage borné
  const score = Math.min(1, Math.max(0, prior + alpha * (target - prior)));

  run(
    `INSERT INTO mastery (user_id, concept_id, score, observations, updated_at) VALUES (?, ?, ?, ?, datetime('now'))
     ON CONFLICT(user_id, concept_id) DO UPDATE SET score = excluded.score, observations = excluded.observations, updated_at = excluded.updated_at`,
    opts.userId, opts.conceptId, score, observations
  );
  return score;
}

/** Score avec décroissance temporelle (demi-vie 14 jours sans activité). */
export function decayedScore(score: number, updatedAt: string): number {
  const days = (Date.now() - new Date(updatedAt + "Z").getTime()) / 86400_000;
  if (!isFinite(days) || days <= 0) return score;
  const decay = Math.pow(0.5, days / 14);
  // On ne retombe jamais sous 40 % du score acquis : l'oubli n'est pas total.
  return score * (0.4 + 0.6 * decay);
}

export type ConceptMastery = {
  conceptId: number;
  slug: string;
  name: string;
  week: number | null;
  importance: number;
  axis: string;
  score: number;
  level: MasteryLevel;
  observations: number;
};

export function masteryForCourse(userId: number, courseCode: string): ConceptMastery[] {
  const rows = all<{
    id: number; slug: string; name: string; week: number | null; importance: number; axis: string;
    score: number | null; observations: number | null; updated_at: string | null;
  }>(
    `SELECT c.id, c.slug, c.name, c.week, c.importance, c.axis, m.score, m.observations, m.updated_at
     FROM concepts c LEFT JOIN mastery m ON m.concept_id = c.id AND m.user_id = ?
     WHERE c.course_code = ? ORDER BY c.week, c.id`,
    userId, courseCode
  );
  return rows.map((r) => {
    const raw = r.score == null ? 0 : decayedScore(r.score, r.updated_at ?? "");
    return {
      conceptId: r.id, slug: r.slug, name: r.name, week: r.week, importance: r.importance, axis: r.axis,
      score: raw, level: levelFor(raw), observations: r.observations ?? 0,
    };
  });
}

/** Profil texte des faiblesses (injecté dans le mode Révision ciblée). */
export function weaknessProfile(userId: number, courseCode: string, max = 8): string {
  const items = masteryForCourse(userId, courseCode)
    .filter((c) => c.observations > 0)
    .sort((a, b) => a.score - b.score)
    .slice(0, max);
  if (!items.length) return "Aucune donnée de pratique encore — commencer par un diagnostic général.";
  return items
    .map((c) => `- ${c.name} (semaine ${c.week ?? "?"}) : maîtrise estimée ${(c.score * 100).toFixed(0)} % (${LEVEL_LABELS[c.level]})`)
    .join("\n");
}