// Phase 22 — Internal Knowledge Library.
//
// Sits on top of the successful-playbook store. Tracks which
// configurations produced which outcomes for which playbook
// signatures, detects fail→succeed error corrections across runs,
// and emits pathway recommendations that the NEXT scenario reads
// at startup.
//
// Event-driven cycle (not wall-clock polling):
//   scenario ends → kb.indexRun() → kb.recommendFor(nextSpec) → next
//   scenario reads top rec and applies.
//
// File layout under data/_kb/:
//   signatures.jsonl            — (sig_hash, embedding[], first_seen, last_seen, run_count)
//   outcomes.jsonl              — append-only per-run: {sig, run_id, models, pathway, ok_events, elapsed_s, errors[]}
//   config_snapshots.jsonl      — config/models.json hash + env at each ingest
//   error_corrections.jsonl     — fail→succeed deltas
//   pathway_recommendations.jsonl — AI-synthesized suggestions
//
// Why file-based: Phase 19 playbook_memory is already in the
// catalogd+vectord stack. This is a separate meta-layer — keeping
// it file-based first lets us iterate quickly without a gateway
// schema migration. Rust port lands once the shape stabilizes
// (mirrors how Phase 21 primitives are TS-first → Rust next sprint).

import { mkdir, readFile, writeFile, appendFile, readdir } from "node:fs/promises";
import { join } from "node:path";
import { createHash } from "node:crypto";
import { SIDECAR, generateContinuable } from "./agent.ts";

const KB_DIR = "data/_kb";
const SIGNATURES_FILE = "signatures.jsonl";
const OUTCOMES_FILE = "outcomes.jsonl";
const CONFIG_SNAPSHOTS_FILE = "config_snapshots.jsonl";
const ERROR_CORRECTIONS_FILE = "error_corrections.jsonl";
const RECOMMENDATIONS_FILE = "pathway_recommendations.jsonl";

// What a playbook signature looks like — stable hash of the scenario
// shape that ignores timestamps and specific worker IDs. Two runs with
// the same sequence of (kind, role, count, city, state) get the same
// hash. This is the retrieval key for the KB.
export interface PlaybookSignature {
  sig_hash: string;
  client: string;
  events_digest: string;       // human-readable event summary
  embedding: number[];         // sidecar embed, for nearest-neighbor
  first_seen: string;
  last_seen: string;
  run_count: number;
}

// What we record after a run completes.
export interface RunOutcome {
  sig_hash: string;
  run_id: string;              // scenario dir basename
  date: string;
  models: {
    executor: string;
    reviewer: string;
    overview: string;
    overview_cloud: boolean;
  };
  ok_events: number;
  total_events: number;
  total_turns: number;
  total_gap_signals: number;
  total_citations: number;
  per_event: Array<{
    at: string;
    kind: string;
    role: string;
    count: number;
    ok: boolean;
    turns: number;
    error: string | null;
  }>;
  elapsed_secs: number;
  created_at: string;
}

// The AI-synthesized recommendation written back for future runs.
export interface PathwayRecommendation {
  sig_hash: string;
  generated_at: string;
  generated_by_model: string;
  confidence: "high" | "medium" | "low";
  rationale: string;           // prose from the recommender
  top_models: {                // suggested tier assignments
    executor?: string;
    reviewer?: string;
    overview?: string;
  };
  budget_hints: {              // suggested max_tokens / think flags
    executor_max_tokens?: number;
    reviewer_max_tokens?: number;
    executor_think?: boolean;
  };
  pathway_notes: string;       // "pre-fetch cert data", "use buffer of 3+"
  neighbors_consulted: string[]; // sig_hashes of the playbooks that shaped this rec
}

// Compute a stable hash from the scenario spec. Two runs with the same
// events list (ignoring SMS drafts / timestamps / exclude lists) get
// the same hash.
export function computeSignature(spec: {
  client: string;
  events: Array<{ kind: string; role: string; count: number; city: string; state: string }>;
}): string {
  const canonical = JSON.stringify({
    client: spec.client,
    events: spec.events.map(e => ({
      kind: e.kind, role: e.role, count: e.count, city: e.city, state: e.state,
    })),
  });
  return createHash("sha256").update(canonical).digest("hex").slice(0, 16);
}

// Human-readable digest of the spec, used in recommender prompts.
export function specDigest(spec: {
  client: string;
  events: Array<{ kind: string; role: string; count: number; city: string; state: string }>;
}): string {
  return `${spec.client}: ` + spec.events.map(e =>
    `${e.kind}/${e.role}×${e.count} in ${e.city},${e.state}`
  ).join(" | ");
}

async function ensureKb(): Promise<void> {
  await mkdir(KB_DIR, { recursive: true });
}

async function readJsonl<T>(file: string): Promise<T[]> {
  try {
    const raw = await readFile(join(KB_DIR, file), "utf8");
    return raw.split("\n").filter(l => l.trim()).map(l => JSON.parse(l) as T);
  } catch {
    return [];
  }
}

// Index a completed scenario run. Extracts signature, computes
// embedding, appends outcome, updates or inserts signature entry.
export async function indexRun(
  scenarioDir: string,
  spec: { client: string; date: string; events: Array<any> },
  models: { executor: string; reviewer: string; overview: string; overview_cloud: boolean },
  elapsed_secs: number,
): Promise<{ sig_hash: string; outcome: RunOutcome }> {
  await ensureKb();

  const sig_hash = computeSignature(spec);
  const digest = specDigest(spec);

  // Read results.json produced by scenario.ts to build the outcome record.
  const resultsRaw = await readFile(join(scenarioDir, "results.json"), "utf8");
  const results = JSON.parse(resultsRaw) as any[];
  const outcome: RunOutcome = {
    sig_hash,
    run_id: scenarioDir.split("/").pop() ?? scenarioDir,
    date: spec.date,
    models,
    ok_events: results.filter(r => r.ok).length,
    total_events: results.length,
    total_turns: results.reduce((s, r) => s + (r.turns ?? 0), 0),
    total_gap_signals: results.reduce((s, r) => s + (r.gap_signals?.length ?? 0), 0),
    total_citations: results.reduce((s, r) => s + (r.playbook_citations?.length ?? 0), 0),
    per_event: results.map(r => ({
      at: r.event.at,
      kind: r.event.kind,
      role: r.event.role,
      count: r.event.count,
      ok: r.ok,
      turns: r.turns ?? 0,
      error: r.error ?? null,
    })),
    elapsed_secs,
    created_at: new Date().toISOString(),
  };
  await appendFile(join(KB_DIR, OUTCOMES_FILE), JSON.stringify(outcome) + "\n");

  // Embed + upsert signature. Skip if embedding fails — the outcome is
  // still persisted, just without neighbor-search hookup.
  try {
    const resp = await fetch(`${SIDECAR}/embed`, {
      method: "POST",
      headers: { "content-type": "application/json" },
      body: JSON.stringify({ texts: [digest] }),
    });
    if (resp.ok) {
      const data: any = await resp.json();
      const embedding: number[] = data.embeddings?.[0] ?? [];
      const existing = await readJsonl<PlaybookSignature>(SIGNATURES_FILE);
      const now = new Date().toISOString();
      const found = existing.find(s => s.sig_hash === sig_hash);
      if (found) {
        found.last_seen = now;
        found.run_count += 1;
      } else {
        existing.push({
          sig_hash,
          client: spec.client,
          events_digest: digest,
          embedding,
          first_seen: now,
          last_seen: now,
          run_count: 1,
        });
      }
      // Rewrite the whole file — cheap while KB is small; swap to
      // append-with-periodic-compact when row count exceeds ~10k.
      await writeFile(
        join(KB_DIR, SIGNATURES_FILE),
        existing.map(s => JSON.stringify(s)).join("\n") + "\n",
      );
    }
  } catch {
    // Signature indexing failed — outcome is still captured. Next
    // indexRun retries.
  }

  return { sig_hash, outcome };
}

// Cosine similarity for neighbor lookup. Float32-in-memory is fine for
// O(thousands) signatures; swap to vectord HNSW once the corpus grows.
function cosine(a: number[], b: number[]): number {
  if (a.length === 0 || a.length !== b.length) return 0;
  let dot = 0, na = 0, nb = 0;
  for (let i = 0; i < a.length; i++) {
    dot += a[i] * b[i];
    na += a[i] * a[i];
    nb += b[i] * b[i];
  }
  return dot / (Math.sqrt(na) * Math.sqrt(nb) + 1e-12);
}

// Find the k nearest-neighbor signatures for a target spec, returning
// neighbor sigs + their outcome history. This is what the recommender
// feeds to the overview model.
export async function findNeighbors(spec: any, k = 5): Promise<Array<{
  sig: PlaybookSignature;
  similarity: number;
  outcomes: RunOutcome[];
}>> {
  await ensureKb();
  const digest = specDigest(spec);
  const targetHash = computeSignature(spec);
  const resp = await fetch(`${SIDECAR}/embed`, {
    method: "POST",
    headers: { "content-type": "application/json" },
    body: JSON.stringify({ texts: [digest] }),
  });
  if (!resp.ok) return [];
  const data: any = await resp.json();
  const targetVec: number[] = data.embeddings?.[0] ?? [];

  const sigs = await readJsonl<PlaybookSignature>(SIGNATURES_FILE);
  const outcomes = await readJsonl<RunOutcome>(OUTCOMES_FILE);

  const ranked = sigs
    .filter(s => s.sig_hash !== targetHash)  // don't recommend against self
    .map(s => ({ sig: s, similarity: cosine(targetVec, s.embedding) }))
    .sort((a, b) => b.similarity - a.similarity)
    .slice(0, k);

  return ranked.map(r => ({
    sig: r.sig,
    similarity: r.similarity,
    outcomes: outcomes.filter(o => o.sig_hash === r.sig.sig_hash),
  }));
}

// Detect fail→succeed pairs within outcomes for the same signature.
// Diff the config/models between them; that's the correction.
export async function detectErrorCorrections(): Promise<Array<{
  sig_hash: string;
  before: RunOutcome;
  after: RunOutcome;
  models_changed: Record<string, { from: string; to: string }>;
}>> {
  const outcomes = await readJsonl<RunOutcome>(OUTCOMES_FILE);
  const bySig = new Map<string, RunOutcome[]>();
  for (const o of outcomes) {
    const arr = bySig.get(o.sig_hash) ?? [];
    arr.push(o);
    bySig.set(o.sig_hash, arr);
  }
  const corrections: any[] = [];
  for (const [sig, runs] of bySig) {
    runs.sort((a, b) => a.created_at.localeCompare(b.created_at));
    for (let i = 1; i < runs.length; i++) {
      const prev = runs[i - 1];
      const cur = runs[i];
      if (prev.ok_events < prev.total_events && cur.ok_events > prev.ok_events) {
        const changed: Record<string, { from: string; to: string }> = {};
        for (const k of ["executor", "reviewer", "overview"] as const) {
          if (prev.models[k] !== cur.models[k]) {
            changed[k] = { from: prev.models[k], to: cur.models[k] };
          }
        }
        corrections.push({ sig_hash: sig, before: prev, after: cur, models_changed: changed });
      }
    }
  }
  return corrections;
}

// Generate a pathway recommendation for a target spec. Reads k-NN
// signatures + their outcome history, asks an overview model to
// synthesize "best path forward", writes to recommendations file.
export async function recommendFor(
  spec: any,
  opts: { overview_model?: string; cloud?: boolean; k?: number } = {},
): Promise<PathwayRecommendation | null> {
  await ensureKb();
  const k = opts.k ?? 5;
  const overviewModel = opts.overview_model ?? "gpt-oss:20b";
  const cloud = opts.cloud ?? false;

  const neighbors = await findNeighbors(spec, k);
  const corrections = await detectErrorCorrections();
  const targetHash = computeSignature(spec);

  if (neighbors.length === 0) {
    // Cold start — no history. Write a minimal rec so next run still
    // gets "we looked" instead of a missing file.
    const rec: PathwayRecommendation = {
      sig_hash: targetHash,
      generated_at: new Date().toISOString(),
      generated_by_model: overviewModel,
      confidence: "low",
      rationale: "No prior runs in KB — first time this signature is seen. Use default model matrix.",
      top_models: {},
      budget_hints: {},
      pathway_notes: "No neighbor history to draw on. Proceed with current config; KB will have data after this run.",
      neighbors_consulted: [],
    };
    await appendFile(join(KB_DIR, RECOMMENDATIONS_FILE), JSON.stringify(rec) + "\n");
    return rec;
  }

  // Build the prompt. Include target spec digest, neighbor digests with
  // their outcome stats, and recent error corrections. Ask for
  // structured output so we can parse it.
  const neighborBlock = neighbors.map(n => {
    const best = n.outcomes.reduce((a, b) =>
      a && a.ok_events / Math.max(1, a.total_events) >= b.ok_events / Math.max(1, b.total_events) ? a : b,
    n.outcomes[0]);
    const avgOk = n.outcomes.length > 0
      ? (n.outcomes.reduce((s, o) => s + o.ok_events, 0) / n.outcomes.length).toFixed(1)
      : "?";
    return `- sig ${n.sig.sig_hash} sim=${n.similarity.toFixed(3)} (${n.sig.events_digest.slice(0, 100)}): ${n.outcomes.length} runs, avg ${avgOk}/${best?.total_events ?? "?"} ok; best models: exec=${best?.models.executor ?? "?"} review=${best?.models.reviewer ?? "?"}`;
  }).join("\n");

  const correctionBlock = corrections.slice(-3).map(c =>
    `- sig ${c.sig_hash}: ${c.before.ok_events}/${c.before.total_events} → ${c.after.ok_events}/${c.after.total_events}; changed=${JSON.stringify(c.models_changed)}`
  ).join("\n") || "(no corrections observed yet)";

  const prompt = `You are the pathway recommender for a staffing coordinator agent system. A new scenario is about to run. Your job: use history of similar runs to recommend the best configuration.

TARGET SCENARIO:
${specDigest(spec)}

${k} NEAREST-NEIGHBOR SIGNATURES FROM HISTORY (by cosine similarity):
${neighborBlock}

RECENT ERROR CORRECTIONS (fail → succeed deltas on same signature):
${correctionBlock}

Your output MUST be a valid JSON object with this shape (and nothing else — no prose before or after):
{
  "confidence": "high" | "medium" | "low",
  "rationale": "2-3 sentence explanation of what pattern you saw",
  "top_models": {"executor": "...", "reviewer": "...", "overview": "..."},
  "budget_hints": {"executor_max_tokens": 800, "reviewer_max_tokens": 600, "executor_think": false},
  "pathway_notes": "concrete pre-run advice — what to pre-fetch, what to avoid, buffer sizes"
}

Respond with ONLY the JSON object.`;

  let raw = "";
  try {
    raw = await generateContinuable(overviewModel, prompt, {
      max_tokens: 1200,
      shape: "json",
      cloud,
      max_continuations: 2,
    });
  } catch (e) {
    return null;
  }

  let parsed: any;
  try {
    const m = raw.match(/\{[\s\S]*\}/);
    parsed = m ? JSON.parse(m[0]) : null;
  } catch {
    parsed = null;
  }
  if (!parsed) return null;

  const rec: PathwayRecommendation = {
    sig_hash: targetHash,
    generated_at: new Date().toISOString(),
    generated_by_model: overviewModel,
    confidence: parsed.confidence ?? "low",
    rationale: String(parsed.rationale ?? "").slice(0, 1000),
    top_models: parsed.top_models ?? {},
    budget_hints: parsed.budget_hints ?? {},
    pathway_notes: String(parsed.pathway_notes ?? "").slice(0, 2000),
    neighbors_consulted: neighbors.map(n => n.sig.sig_hash),
  };
  await appendFile(join(KB_DIR, RECOMMENDATIONS_FILE), JSON.stringify(rec) + "\n");
  return rec;
}

// Read-back at scenario start: find the newest recommendation for this
// exact sig_hash (or nearest neighbor of it). Returns null if nothing
// applicable found.
export async function loadRecommendation(spec: any): Promise<PathwayRecommendation | null> {
  await ensureKb();
  const targetHash = computeSignature(spec);
  const recs = await readJsonl<PathwayRecommendation>(RECOMMENDATIONS_FILE);
  const matching = recs.filter(r => r.sig_hash === targetHash);
  if (matching.length === 0) return null;
  matching.sort((a, b) => b.generated_at.localeCompare(a.generated_at));
  return matching[0];
}

// Record a config snapshot. Called whenever models.json or the active
// model assignments change, so error-correction diffs have history to
// reference beyond the outcomes file.
export async function snapshotConfig(
  models_json_hash: string,
  active_models: Record<string, string>,
  why: string,
): Promise<void> {
  await ensureKb();
  await appendFile(
    join(KB_DIR, CONFIG_SNAPSHOTS_FILE),
    JSON.stringify({
      at: new Date().toISOString(),
      models_json_hash,
      active_models,
      why,
    }) + "\n",
  );
}