import { mkdir, readFile, rename, stat, writeFile } from "node:fs/promises";
import { dirname } from "node:path";

import type { MemoryOpenVikingConfig } from "./config.js";
import { normalizeRecallResourceTypes, type RecallResourceType } from "./registries/recall-resource-types.js";

export type RuntimeQueryParams = {
  recallLimit?: number;
  candidateLimit?: number;
  candidateMultiplier?: number;
  scoreThreshold?: number;
  maxInjectedChars?: number;
  recallPreferAbstract?: boolean;
  resourceTypes?: RecallResourceType[] | string;
  targetUri?: string;
  ovSearchLimit?: number;
  rankingWeights?: {
    baseScore?: number;
    leaf?: number;
    event?: number;
    preference?: number;
    lexicalOverlapMax?: number;
  };
  resourceTypeWeights?: Partial<Record<RecallResourceType, number>>;
  categoryWeights?: Record<string, number>;
};

type RuntimeQueryParamsPatch = RuntimeQueryParams & Record<string, unknown>;
type ConfigSource = "request" | "session" | "claw" | "static" | "default";
type RuntimeScope = "claw" | "session";

export type QueryConfigContext = {
  peerId: string;
  sessionId?: string;
  sessionKey?: string;
  ovSessionId?: string;
};

export type EffectiveQueryConfig = {
  recallLimit: number;
  candidateLimit: number;
  candidateMultiplier: number;
  scoreThreshold: number;
  maxInjectedChars: number;
  recallPreferAbstract: boolean;
  resourceTypes: RecallResourceType[];
  targetUri?: string;
  ovSearchLimit: number;
  rankingWeights: {
    baseScore: number;
    leaf: number;
    event: number;
    preference: number;
    lexicalOverlapMax: number;
  };
  resourceTypeWeights: Record<string, number>;
  categoryWeights: Record<string, number>;
  sources: Record<string, ConfigSource>;
  warnings: string[];
};

type RuntimeRecord = {
  params: RuntimeQueryParams;
  updatedAt: number;
  updatedBy?: string;
  peerId?: string;
  expiresAt?: number;
};

type RuntimeFile = {
  schemaVersion: "1.0";
  updatedAt: number;
  claws: Record<string, RuntimeRecord>;
  sessions: Record<string, RuntimeRecord>;
};

const DEFAULT_CANDIDATE_MULTIPLIER = 4;
const DEFAULT_OV_SEARCH_LIMIT = 10;
const DEFAULT_RANKING_WEIGHTS = {
  baseScore: 1,
  leaf: 0.12,
  event: 0.1,
  preference: 0.08,
  lexicalOverlapMax: 0.2,
};

function toNumber(value: unknown): number | undefined {
  if (typeof value === "number" && Number.isFinite(value)) return value;
  if (typeof value === "string" && value.trim() !== "") {
    const parsed = Number(value);
    if (Number.isFinite(parsed)) return parsed;
  }
  return undefined;
}

function clampInteger(value: unknown, min: number, max: number): number | undefined {
  const n = toNumber(value);
  if (n === undefined) return undefined;
  return Math.max(min, Math.min(max, Math.floor(n)));
}

function clampNumber(value: unknown, min: number, max: number): number | undefined {
  const n = toNumber(value);
  if (n === undefined) return undefined;
  return Math.max(min, Math.min(max, n));
}

function shallowNumberRecord(value: unknown, min: number, max: number): Record<string, number> | undefined {
  if (!value || typeof value !== "object" || Array.isArray(value)) return undefined;
  const result: Record<string, number> = {};
  for (const [key, raw] of Object.entries(value)) {
    const n = clampNumber(raw, min, max);
    if (n !== undefined) result[key] = n;
  }
  return result;
}

export function normalizeRuntimeQueryParams(value: RuntimeQueryParamsPatch): { params: RuntimeQueryParams; warnings: string[] } {
  const warnings: string[] = [];
  const params: RuntimeQueryParams = {};

  const recallLimit = clampInteger(value.recallLimit, 1, 50);
  if (recallLimit !== undefined) params.recallLimit = recallLimit;
  const candidateMultiplier = clampInteger(value.candidateMultiplier, 1, 20);
  if (candidateMultiplier !== undefined) params.candidateMultiplier = candidateMultiplier;
  const candidateLimit = clampInteger(value.candidateLimit, 1, 200);
  if (candidateLimit !== undefined) params.candidateLimit = candidateLimit;
  const scoreThreshold = clampNumber(value.scoreThreshold, 0, 1);
  if (scoreThreshold !== undefined) params.scoreThreshold = scoreThreshold;
  const maxInjectedChars = clampInteger(value.maxInjectedChars, 100, 50_000);
  if (maxInjectedChars !== undefined) params.maxInjectedChars = maxInjectedChars;
  const ovSearchLimit = clampInteger(value.ovSearchLimit, 1, 100);
  if (ovSearchLimit !== undefined) params.ovSearchLimit = ovSearchLimit;

  if (typeof value.recallPreferAbstract === "boolean") params.recallPreferAbstract = value.recallPreferAbstract;
  if (value.resourceTypes !== undefined) params.resourceTypes = normalizeRecallResourceTypes(value.resourceTypes);
  if (typeof value.targetUri === "string" && value.targetUri.trim()) {
    const targetUri = value.targetUri.trim();
    if (!targetUri.startsWith("viking://")) throw new Error("targetUri must start with viking://");
    params.targetUri = targetUri;
  }

  const rankingWeights = shallowNumberRecord(value.rankingWeights, 0, 2);
  if (rankingWeights) params.rankingWeights = rankingWeights;
  const resourceTypeWeights = shallowNumberRecord(value.resourceTypeWeights, -1, 2);
  if (resourceTypeWeights) params.resourceTypeWeights = resourceTypeWeights as Partial<Record<RecallResourceType, number>>;
  const categoryWeights = shallowNumberRecord(value.categoryWeights, -1, 2);
  if (categoryWeights) params.categoryWeights = categoryWeights;

  if (params.candidateLimit !== undefined && params.recallLimit !== undefined && params.candidateLimit < params.recallLimit) {
    params.candidateLimit = params.recallLimit;
    warnings.push("candidateLimit was raised to recallLimit");
  }

  return { params, warnings };
}

export function resolveSessionQueryConfigKey(ctx: Partial<QueryConfigContext>): string | undefined {
  if (ctx.ovSessionId) return `ov:${ctx.ovSessionId}`;
  if (ctx.sessionId) return `session:${ctx.sessionId}`;
  if (ctx.sessionKey) return `key:${ctx.sessionKey}`;
  return undefined;
}

function emptyRuntimeFile(): RuntimeFile {
  return { schemaVersion: "1.0", updatedAt: Date.now(), claws: {}, sessions: {} };
}

function isRuntimeFile(value: unknown): value is RuntimeFile {
  return !!value && typeof value === "object" && !Array.isArray(value) && (value as RuntimeFile).schemaVersion === "1.0";
}

export class RuntimeQueryConfigStore {
  private data: RuntimeFile = emptyRuntimeFile();
  private lastMtimeMs = 0;
  private loadPromise: Promise<void> | undefined;
  private writeQueue: Promise<void> = Promise.resolve();

  static createInMemory(staticConfig: Required<MemoryOpenVikingConfig>): RuntimeQueryConfigStore {
    return new RuntimeQueryConfigStore({ staticConfig });
  }

  constructor(private readonly options: { staticConfig: Required<MemoryOpenVikingConfig>; path?: string }) {}

  async load(): Promise<void> {
    if (!this.options.path) return;
    const loadPromise = this.loadFromDisk({ resetOnFailure: true });
    this.loadPromise = loadPromise;
    try {
      await loadPromise;
    } finally {
      if (this.loadPromise === loadPromise) this.loadPromise = undefined;
    }
  }

  private async loadFromDisk(options?: { resetOnFailure?: boolean }): Promise<void> {
    try {
      const raw = await readFile(this.options.path!, "utf8");
      const parsed = JSON.parse(raw);
      if (isRuntimeFile(parsed)) this.data = parsed;
      const s = await stat(this.options.path!);
      this.lastMtimeMs = s.mtimeMs;
    } catch {
      if (options?.resetOnFailure) this.data = emptyRuntimeFile();
    }
  }

  private async waitForInitialLoad(): Promise<void> {
    if (this.loadPromise) await this.loadPromise;
  }

  async reloadIfChanged(options?: { force?: boolean }): Promise<void> {
    if (!this.options.path) return;
    await this.waitForInitialLoad();
    try {
      const s = await stat(this.options.path);
      if (!options?.force && s.mtimeMs === this.lastMtimeMs) return;
      const raw = await readFile(this.options.path, "utf8");
      const parsed = JSON.parse(raw);
      if (isRuntimeFile(parsed)) {
        this.data = parsed;
        this.lastMtimeMs = s.mtimeMs;
      }
    } catch {
      // Keep the last known-good in-memory config.
    }
  }

  async set(scope: RuntimeScope, ctx: QueryConfigContext, patch: RuntimeQueryParamsPatch): Promise<{ warnings: string[] }> {
    await this.waitForInitialLoad();
    const { params, warnings } = normalizeRuntimeQueryParams(patch);
    const key = this.keyForScope(scope, ctx);
    const bucket = scope === "claw" ? this.data.claws : this.data.sessions;
    const previous = bucket[key];
    bucket[key] = {
      params: { ...(previous?.params ?? {}), ...params },
      updatedAt: Date.now(),
      updatedBy: "command",
      peerId: ctx.peerId,
    };
    this.data.updatedAt = Date.now();
    await this.persist();
    return { warnings };
  }

  async unset(scope: RuntimeScope, ctx: QueryConfigContext, fields: string[]): Promise<void> {
    await this.waitForInitialLoad();
    const key = this.keyForScope(scope, ctx);
    const bucket = scope === "claw" ? this.data.claws : this.data.sessions;
    const record = bucket[key];
    if (!record) return;
    for (const field of fields) {
      delete (record.params as Record<string, unknown>)[field];
    }
    record.updatedAt = Date.now();
    this.data.updatedAt = Date.now();
    await this.persist();
  }

  async reset(scope: RuntimeScope, ctx: QueryConfigContext): Promise<void> {
    await this.waitForInitialLoad();
    const key = this.keyForScope(scope, ctx);
    const bucket = scope === "claw" ? this.data.claws : this.data.sessions;
    delete bucket[key];
    this.data.updatedAt = Date.now();
    await this.persist();
  }

  async getEffective(ctx: QueryConfigContext, requestOverrides?: RuntimeQueryParamsPatch): Promise<EffectiveQueryConfig> {
    await this.reloadIfChanged();
    const cfg = this.options.staticConfig;
    const warnings: string[] = [];
    const effective: EffectiveQueryConfig = {
      recallLimit: cfg.recallLimit,
      candidateMultiplier: DEFAULT_CANDIDATE_MULTIPLIER,
      candidateLimit: Math.max(cfg.recallLimit * DEFAULT_CANDIDATE_MULTIPLIER, 20),
      scoreThreshold: cfg.recallScoreThreshold,
      maxInjectedChars: cfg.recallMaxInjectedChars,
      recallPreferAbstract: cfg.recallPreferAbstract,
      resourceTypes: normalizeRecallResourceTypes(cfg.recallTargetTypes),
      ovSearchLimit: DEFAULT_OV_SEARCH_LIMIT,
      rankingWeights: { ...DEFAULT_RANKING_WEIGHTS },
      resourceTypeWeights: {},
      categoryWeights: {},
      sources: {
        recallLimit: "static",
        candidateMultiplier: "default",
        candidateLimit: "default",
        scoreThreshold: "static",
        maxInjectedChars: "static",
        recallPreferAbstract: "static",
        resourceTypes: "static",
        ovSearchLimit: "default",
        rankingWeights: "default",
      },
      warnings,
    };

    let candidateLimitExplicit = false;
    candidateLimitExplicit = this.applyLayer(effective, this.data.claws[ctx.peerId]?.params, "claw", candidateLimitExplicit);
    const sessionRecord = this.findSessionRecord(ctx);
    if (sessionRecord) candidateLimitExplicit = this.applyLayer(effective, sessionRecord.params, "session", candidateLimitExplicit);
    if (requestOverrides) {
      const normalized = normalizeRuntimeQueryParams(requestOverrides);
      warnings.push(...normalized.warnings);
      this.applyLayer(effective, normalized.params, "request", candidateLimitExplicit);
    }
    effective.candidateLimit = Math.max(effective.candidateLimit, effective.recallLimit);
    return effective;
  }

  private applyLayer(
    effective: EffectiveQueryConfig,
    params: RuntimeQueryParams | undefined,
    source: ConfigSource,
    candidateLimitExplicit: boolean,
  ): boolean {
    if (!params) return candidateLimitExplicit;
    if (params.recallLimit !== undefined) {
      effective.recallLimit = params.recallLimit;
      effective.sources.recallLimit = source;
      if (!candidateLimitExplicit) {
        effective.candidateLimit = Math.max(effective.recallLimit * effective.candidateMultiplier, 20);
        effective.sources.candidateLimit = source;
      }
    }
    if (params.candidateMultiplier !== undefined) {
      effective.candidateMultiplier = params.candidateMultiplier;
      effective.sources.candidateMultiplier = source;
      if (!candidateLimitExplicit) {
        effective.candidateLimit = Math.max(effective.recallLimit * params.candidateMultiplier, 20);
        effective.sources.candidateLimit = source;
      }
    }
    if (params.candidateLimit !== undefined) {
      effective.candidateLimit = params.candidateLimit;
      effective.sources.candidateLimit = source;
      candidateLimitExplicit = true;
    }
    if (params.scoreThreshold !== undefined) {
      effective.scoreThreshold = params.scoreThreshold;
      effective.sources.scoreThreshold = source;
    }
    if (params.maxInjectedChars !== undefined) {
      effective.maxInjectedChars = params.maxInjectedChars;
      effective.sources.maxInjectedChars = source;
    }
    if (params.recallPreferAbstract !== undefined) {
      effective.recallPreferAbstract = params.recallPreferAbstract;
      effective.sources.recallPreferAbstract = source;
    }
    if (params.resourceTypes !== undefined) {
      effective.resourceTypes = Array.isArray(params.resourceTypes) ? [...params.resourceTypes] : normalizeRecallResourceTypes(params.resourceTypes);
      effective.sources.resourceTypes = source;
    }
    if (params.targetUri !== undefined) {
      effective.targetUri = params.targetUri;
      effective.sources.targetUri = source;
    }
    if (params.ovSearchLimit !== undefined) {
      effective.ovSearchLimit = params.ovSearchLimit;
      effective.sources.ovSearchLimit = source;
    }
    if (params.rankingWeights) {
      effective.rankingWeights = { ...effective.rankingWeights, ...params.rankingWeights };
      effective.sources.rankingWeights = source;
    }
    if (params.resourceTypeWeights) effective.resourceTypeWeights = { ...effective.resourceTypeWeights, ...params.resourceTypeWeights };
    if (params.categoryWeights) effective.categoryWeights = { ...effective.categoryWeights, ...params.categoryWeights };
    return candidateLimitExplicit;
  }

  private keyForScope(scope: RuntimeScope, ctx: QueryConfigContext): string {
    if (scope === "claw") return ctx.peerId;
    const key = resolveSessionQueryConfigKey(ctx);
    if (!key) throw new Error("session scope requires ovSessionId, sessionId, or sessionKey");
    return key;
  }

  private findSessionRecord(ctx: QueryConfigContext): RuntimeRecord | undefined {
    const keys = [
      ctx.ovSessionId ? `ov:${ctx.ovSessionId}` : undefined,
      ctx.sessionId ? `session:${ctx.sessionId}` : undefined,
      ctx.sessionKey ? `key:${ctx.sessionKey}` : undefined,
    ].filter((key): key is string => Boolean(key));
    for (const key of keys) {
      const record = this.data.sessions[key];
      if (record) return record;
    }
    return undefined;
  }

  private async persist(): Promise<void> {
    if (!this.options.path) return;
    const operation = this.writeQueue.catch(() => undefined).then(async () => {
      await mkdir(dirname(this.options.path!), { recursive: true });
      const temp = `${this.options.path}.${process.pid}.${Date.now()}.tmp`;
      await writeFile(temp, JSON.stringify(this.data, null, 2), "utf8");
      await rename(temp, this.options.path!);
      const s = await stat(this.options.path!);
      this.lastMtimeMs = s.mtimeMs;
    });
    this.writeQueue = operation.catch(() => undefined);
    await operation;
  }
}