/**
 * Long-term cross-session memory service.
 *
 * Owns CRUD against `user_memory_facts`, normalisation/dedupe, the
 * per-turn ranker (salience × recency × keyword overlap, no embeddings),
 * a cheap token estimator, and the hard caps that apply regardless of
 * what the user's settings say:
 *
 *   - at most 100 stored facts per user (eviction = lowest salience,
 *     then oldest, on insert overflow);
 *   - at most ~2000 tokens injected into the system prompt per turn;
 *   - at most 5 newly auto-extracted facts persisted per turn (manual
 *     creates from the user are not counted against this).
 */
import { and, desc, eq, sql } from "drizzle-orm";
import {
  db,
  userMemoryFacts,
  userSettings,
  type UserMemoryFact,
  type UserSettingsBlob,
} from "@workspace/db";
import { newId } from "./ids";
import { defaultSettings } from "./defaults";
import {
  MEMORY_HARD_CAPS,
  VALID_KINDS,
  contentHash,
  estimateTokens,
  normalize,
  rankAndPackFacts,
  type MemoryConfig,
  type MemoryInjection,
  type PublicMemoryFact,
} from "./memory-core";

// Re-export the pure helpers + types so existing call sites keep working.
export {
  MEMORY_HARD_CAPS,
  VALID_KINDS,
  contentHash,
  estimateTokens,
  normalize,
  rankAndPackFacts,
  type MemoryConfig,
  type MemoryInjection,
  type PublicMemoryFact,
};

function clampKind(kind: string | undefined | null): string {
  if (!kind) return "fact";
  return VALID_KINDS.has(kind) ? kind : "fact";
}

function clampUnit(n: unknown, dflt: number): number {
  if (typeof n !== "number" || !Number.isFinite(n)) return dflt;
  if (n < 0) return 0;
  if (n > 1) return 1;
  return n;
}

function clampContent(s: string): string {
  const t = String(s || "").trim();
  return t.length > MEMORY_HARD_CAPS.contentChars
    ? t.slice(0, MEMORY_HARD_CAPS.contentChars)
    : t;
}

function clampMaxFacts(n: unknown): number {
  if (typeof n !== "number" || !Number.isFinite(n)) return MEMORY_HARD_CAPS.facts;
  return Math.max(1, Math.min(MEMORY_HARD_CAPS.facts, Math.floor(n)));
}

function clampMaxTokens(n: unknown): number {
  if (typeof n !== "number" || !Number.isFinite(n)) {
    return MEMORY_HARD_CAPS.tokensPerTurn;
  }
  return Math.max(0, Math.min(MEMORY_HARD_CAPS.tokensPerTurn, Math.floor(n)));
}

function toPublic(row: UserMemoryFact): PublicMemoryFact {
  return {
    id: row.id,
    kind: row.kind,
    content: row.content,
    confidence: row.confidence,
    salience: row.salience,
    source: (row.source as "auto" | "manual") || "auto",
    source_message_id: row.sourceMessageId,
    conversation_id: row.conversationId,
    use_count: row.useCount,
    archived: !!row.archived,
    created_at: row.createdAt.toISOString(),
    updated_at: row.updatedAt.toISOString(),
    last_used_at: row.lastUsedAt ? row.lastUsedAt.toISOString() : null,
  };
}

// ---------- settings

export async function getMemoryConfig(userId: string): Promise<MemoryConfig> {
  const rows = await db
    .select()
    .from(userSettings)
    .where(eq(userSettings.userId, userId))
    .limit(1);
  const blob = (rows[0]?.data ?? defaultSettings()) as UserSettingsBlob;
  const m = blob.long_term_memory ?? defaultSettings().long_term_memory;
  return {
    enabled: !!m.enabled,
    auto_extract: m.auto_extract !== false,
    max_facts: clampMaxFacts(m.max_facts),
    max_tokens_per_turn: clampMaxTokens(m.max_tokens_per_turn),
  };
}

// ---------- CRUD

export async function listFacts(
  userId: string,
  opts: { includeArchived?: boolean } = {},
): Promise<PublicMemoryFact[]> {
  const where = opts.includeArchived
    ? eq(userMemoryFacts.userId, userId)
    : and(
        eq(userMemoryFacts.userId, userId),
        eq(userMemoryFacts.archived, 0),
      );
  const rows = await db
    .select()
    .from(userMemoryFacts)
    .where(where)
    .orderBy(desc(userMemoryFacts.salience), desc(userMemoryFacts.updatedAt));
  return rows.map(toPublic);
}

export async function countFacts(
  userId: string,
  opts: { includeArchived?: boolean } = {},
): Promise<number> {
  const where = opts.includeArchived
    ? eq(userMemoryFacts.userId, userId)
    : and(
        eq(userMemoryFacts.userId, userId),
        eq(userMemoryFacts.archived, 0),
      );
  const rows = await db
    .select({ n: sql<number>`count(*)::int` })
    .from(userMemoryFacts)
    .where(where);
  return rows[0]?.n ?? 0;
}

/** Soft-archive a fact: hidden from listing/ranking, kept on disk. */
export async function archiveFact(
  userId: string,
  id: string,
): Promise<PublicMemoryFact | null> {
  await db
    .update(userMemoryFacts)
    .set({ archived: 1, updatedAt: new Date() })
    .where(
      and(eq(userMemoryFacts.id, id), eq(userMemoryFacts.userId, userId)),
    );
  const rows = await db
    .select()
    .from(userMemoryFacts)
    .where(
      and(eq(userMemoryFacts.id, id), eq(userMemoryFacts.userId, userId)),
    )
    .limit(1);
  return rows[0] ? toPublic(rows[0]) : null;
}

/** Restore an archived fact. */
export async function unarchiveFact(
  userId: string,
  id: string,
): Promise<PublicMemoryFact | null> {
  await db
    .update(userMemoryFacts)
    .set({ archived: 0, updatedAt: new Date() })
    .where(
      and(eq(userMemoryFacts.id, id), eq(userMemoryFacts.userId, userId)),
    );
  const rows = await db
    .select()
    .from(userMemoryFacts)
    .where(
      and(eq(userMemoryFacts.id, id), eq(userMemoryFacts.userId, userId)),
    )
    .limit(1);
  return rows[0] ? toPublic(rows[0]) : null;
}

interface CreateArgs {
  kind?: string;
  content: string;
  confidence?: number;
  salience?: number;
  source?: "auto" | "manual";
  sourceMessageId?: string | null;
  conversationId?: string | null;
}

/**
 * Insert a new fact, deduping by `normalized`. Returns the (possibly
 * pre-existing) fact along with a flag indicating whether a brand-new
 * row was created vs. an existing one was bumped. Enforces the per-user
 * `max_facts` cap by evicting the lowest-salience, then oldest, fact.
 */
export async function createOrBumpFact(
  userId: string,
  args: CreateArgs,
  cfg: MemoryConfig,
): Promise<{ fact: PublicMemoryFact; created: boolean }> {
  const content = clampContent(args.content);
  if (!content) {
    throw new Error("content is required");
  }
  const normalized = normalize(content);
  if (!normalized) {
    throw new Error("content is empty after normalisation");
  }
  const hash = contentHash(content);
  // Dedupe by stable hash first (cheap, index-friendly), fall back to
  // normalized text for legacy rows without a hash. Re-emitting an
  // archived fact also un-archives it.
  const existing = await db
    .select()
    .from(userMemoryFacts)
    .where(
      and(
        eq(userMemoryFacts.userId, userId),
        sql`(${userMemoryFacts.contentHash} = ${hash} OR (${userMemoryFacts.contentHash} = '' AND ${userMemoryFacts.normalized} = ${normalized}))`,
      ),
    )
    .limit(1);
  if (existing[0]) {
    const row = existing[0];
    const newSalience = Math.min(
      1,
      Math.max(row.salience, clampUnit(args.salience, row.salience) + 0.05),
    );
    const newConfidence = Math.max(
      row.confidence,
      clampUnit(args.confidence, row.confidence),
    );
    await db
      .update(userMemoryFacts)
      .set({
        salience: newSalience,
        confidence: newConfidence,
        useCount: row.useCount + 1,
        contentHash: hash,
        archived: 0,
        updatedAt: new Date(),
      })
      .where(eq(userMemoryFacts.id, row.id));
    const refreshed = (await db
      .select()
      .from(userMemoryFacts)
      .where(eq(userMemoryFacts.id, row.id))
      .limit(1))[0]!;
    return { fact: toPublic(refreshed), created: false };
  }

  // Eviction: enforce max_facts cap before insert. Archive the lowest
  // salience / oldest active rows rather than hard-deleting them.
  const cap = Math.min(cfg.max_facts, MEMORY_HARD_CAPS.facts);
  const total = await countFacts(userId);
  if (total >= cap) {
    const victims = await db
      .select({ id: userMemoryFacts.id })
      .from(userMemoryFacts)
      .where(
        and(
          eq(userMemoryFacts.userId, userId),
          eq(userMemoryFacts.archived, 0),
        ),
      )
      .orderBy(userMemoryFacts.salience, userMemoryFacts.createdAt)
      .limit(total - cap + 1);
    if (victims.length) {
      const ids = victims.map((v) => v.id);
      for (const id of ids) {
        await db
          .update(userMemoryFacts)
          .set({ archived: 1, updatedAt: new Date() })
          .where(eq(userMemoryFacts.id, id));
      }
    }
  }
  const id = newId("memf");
  const row = {
    id,
    userId,
    kind: clampKind(args.kind),
    content,
    normalized,
    contentHash: hash,
    archived: 0,
    confidence: clampUnit(args.confidence, 0.7),
    salience: clampUnit(args.salience, args.source === "manual" ? 0.9 : 0.6),
    source: args.source === "manual" ? "manual" : "auto",
    sourceMessageId: args.sourceMessageId ?? null,
    conversationId: args.conversationId ?? null,
    useCount: 0,
  };
  await db.insert(userMemoryFacts).values(row);
  const inserted = (await db
    .select()
    .from(userMemoryFacts)
    .where(eq(userMemoryFacts.id, id))
    .limit(1))[0]!;
  return { fact: toPublic(inserted), created: true };
}

export async function updateFact(
  userId: string,
  id: string,
  patch: { kind?: string; content?: string; salience?: number },
): Promise<PublicMemoryFact | null> {
  const rows = await db
    .select()
    .from(userMemoryFacts)
    .where(
      and(eq(userMemoryFacts.id, id), eq(userMemoryFacts.userId, userId)),
    )
    .limit(1);
  if (!rows[0]) return null;
  const existing = rows[0];
  const set: Partial<typeof userMemoryFacts.$inferInsert> & {
    updatedAt: Date;
  } = { updatedAt: new Date() };
  if (typeof patch.kind === "string") set.kind = clampKind(patch.kind);
  if (typeof patch.content === "string") {
    const c = clampContent(patch.content);
    if (!c) throw new Error("content is required");
    set.content = c;
    set.normalized = normalize(c);
    set.contentHash = contentHash(c);
  }
  if (typeof patch.salience === "number") {
    set.salience = clampUnit(patch.salience, existing.salience);
  }
  await db
    .update(userMemoryFacts)
    .set(set)
    .where(eq(userMemoryFacts.id, id));
  const refreshed = (await db
    .select()
    .from(userMemoryFacts)
    .where(eq(userMemoryFacts.id, id))
    .limit(1))[0]!;
  return toPublic(refreshed);
}

export async function deleteFact(
  userId: string,
  id: string,
): Promise<boolean> {
  const res = await db
    .delete(userMemoryFacts)
    .where(
      and(eq(userMemoryFacts.id, id), eq(userMemoryFacts.userId, userId)),
    );
  // Drizzle `delete` returns driver-specific shape; treat any throw as a
  // failure and otherwise assume success.
  return !!res;
}

export async function clearFacts(userId: string): Promise<number> {
  const before = await countFacts(userId);
  await db.delete(userMemoryFacts).where(eq(userMemoryFacts.userId, userId));
  return before;
}

// ---------- ranking + injection
//
// The pure ranker, prompt fragments, tokenizer and stopword list now
// live in `./memory-core.ts` so they can be unit-tested without
// pulling in `@workspace/db`. The async wrapper below loads the user's
// facts and delegates to `rankAndPackFacts`.

export async function rankFactsForTurn(
  userId: string,
  currentText: string,
  cfg: MemoryConfig,
): Promise<MemoryInjection> {
  if (!cfg.enabled) {
    return { facts: [], fact_ids: [], injected_tokens: 0, text: null };
  }
  const all = await listFacts(userId);
  return rankAndPackFacts(all, currentText, cfg);
}

export async function touchFacts(
  userId: string,
  factIds: string[],
): Promise<void> {
  if (!factIds.length) return;
  const now = new Date();
  for (const id of factIds) {
    await db
      .update(userMemoryFacts)
      .set({
        lastUsedAt: now,
        useCount: sql`${userMemoryFacts.useCount} + 1`,
      })
      .where(
        and(
          eq(userMemoryFacts.id, id),
          eq(userMemoryFacts.userId, userId),
        ),
      );
  }
}