/**
 * V9 deterministic engine client (Python, server-side only).
 *
 * The Python service owns Event Contract v2 normalization, candidate ranking,
 * decision policy and the execution ledger. This client validates and projects
 * that server contract; it never reconstructs rank, support, ties, confidence,
 * permissions or executed methods from raw scores or event domains.
 */

import {
  isBackgroundEvidenceKind,
  isEvidenceDomain,
  isEvidenceKind,
  type EvidenceKind,
} from "./evidence-model";
import {
  isPublicRectificationMethod,
  type PublicRectificationMethod,
} from "./public-receipt";

export class RectificationEngineError extends Error {
  readonly code: string;

  constructor(code: string, message: string) {
    super(message);
    this.name = "RectificationEngineError";
    this.code = code;
  }
}

export type V9EngineEvent = Readonly<{
  id: string;
  domain: string;
  event_kind: string;
  date_start: string;
  date_end: string;
  precision: "day" | "month" | "quarter" | "year" | "range";
  summary: string;
  date_source?: string | null;
  date_reliability?: string | null;
  date_corroboration?: string | null;
  date_conflict_status?: string | null;
  source_turn_id?: string | null;
  subject?: string | null;
}>;

export type V9EngineCandidate = Readonly<{
  candidateId: string;
  time: string;
  rank: number;
  relativeSupport: number;
  tiedMinuteCount: number;
}>;

export type V9DecisionReceipt = Readonly<Record<string, unknown>>;
export type V9ExecutionLedger = readonly Readonly<Record<string, unknown>>[];

export type V9EngineScoreResult = Readonly<{
  engineResultId: string;
  algorithmVersion: string;
  eventContractVersion: string;
  policyVersion: string;
  candidateRange: { start_time: string; end_time: string };
  candidates: readonly V9EngineCandidate[];
  overallConfidence: "low" | "medium" | "high";
  marginPercent: number | null;
  selectionAllowed: boolean;
  confirmationAllowed: boolean;
  representativeCandidateId: string | null;
  representativeTime: string | null;
  decisionReceipt: V9DecisionReceipt;
  executionLedger: V9ExecutionLedger;
  executedMethods: readonly PublicRectificationMethod[];
}>;

export type V9EngineDiagnostics = Readonly<{
  algorithmVersion: string;
  engineResultId: string;
  eventContractVersion: string;
  policyVersion: string;
  diagnostics: Readonly<Record<string, unknown>>;
  missingLayers: readonly string[];
  canConfirmExactMinute: boolean;
  decisionReceipt: V9DecisionReceipt;
  executionLedger: V9ExecutionLedger;
  executedMethods: readonly PublicRectificationMethod[];
}>;

const EVENT_CONTRACT_VERSION = "rectification-event-contract-v2";
const RECEIPT_VERSION = "candidate-decision-receipt-v2";
const EXECUTION_LEDGER_VERSION = "rectification-execution-ledger-v2";
const timePattern = /^(?:[01]\d|2[0-3]):[0-5]\d$/;
const uuidPattern = /^[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i;

function record(value: unknown): Record<string, unknown> | null {
  return value && typeof value === "object" && !Array.isArray(value)
    ? value as Record<string, unknown>
    : null;
}

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

function clockMinute(value: string): number {
  const [hour = 0, minute = 0] = value.split(":").map(Number);
  return hour * 60 + minute;
}

function timeInRange(time: string, range: { start_time: string; end_time: string }): boolean {
  const value = clockMinute(time);
  const start = clockMinute(range.start_time);
  const end = clockMinute(range.end_time);
  return end >= start ? value >= start && value <= end : value >= start || value <= end;
}

/** Map a V9 evidence date precision to the Event Contract v2 vocabulary. */
export function enginePrecision(precision: string): V9EngineEvent["precision"] {
  if (precision === "day" || precision === "month" || precision === "quarter" || precision === "range") {
    return precision;
  }
  return "year";
}

export function toEngineEvents(
  evidence: readonly Readonly<{
    id: string;
    eventKind: string;
    domain: string;
    occurredFrom: string | null;
    occurredTo: string | null;
    datePrecision: string;
    summary: string;
    dateSource?: string | null;
    dateReliability?: string | null;
    dateCorroboration?: string | null;
    dateConflictStatus?: string | null;
    sourceTurnId?: string | null;
    subject?: string | null;
  }>[],
): V9EngineEvent[] {
  return evidence.flatMap((item): V9EngineEvent[] => {
    if (!isEvidenceKind(item.eventKind) || !isEvidenceDomain(item.domain)) return [];
    if (isBackgroundEvidenceKind(item.eventKind as EvidenceKind)) return [];
    const start = item.occurredFrom ?? item.occurredTo;
    const end = item.occurredTo ?? item.occurredFrom;
    if (!start) return [];
    return [{
      id: item.id,
      domain: item.domain,
      event_kind: item.eventKind,
      date_start: start.slice(0, 10),
      date_end: (end ?? start).slice(0, 10),
      precision: enginePrecision(item.datePrecision),
      summary: item.summary,
      date_source: item.dateSource ?? null,
      date_reliability: item.dateReliability ?? null,
      date_corroboration: item.dateCorroboration ?? null,
      date_conflict_status: item.dateConflictStatus ?? null,
      source_turn_id: item.sourceTurnId ?? null,
      subject: item.subject ?? null,
    }];
  });
}

function engineBase(): string {
  return process.env.JYOTISH_API_BASE?.trim() || "http://127.0.0.1:5200";
}

async function postEngine(path: string, body: unknown, timeoutMs = 60_000): Promise<Record<string, unknown>> {
  const response = await fetch(`${engineBase()}${path}`, {
    method: "POST",
    headers: { "content-type": "application/json" },
    body: JSON.stringify(body),
    signal: AbortSignal.timeout(timeoutMs),
  });
  const data = await response.json().catch(() => null);
  if (!response.ok) {
    const message = data && typeof data === "object"
      ? String((data as Record<string, unknown>).error ?? (data as Record<string, unknown>).message ?? `Jyotish API ${response.status}`)
      : `Jyotish API ${response.status}`;
    throw new RectificationEngineError("engine_request_failed", message);
  }
  if (!data || typeof data !== "object") {
    throw new RectificationEngineError("engine_invalid_response", "Jyotish API returned an invalid response");
  }
  return data as Record<string, unknown>;
}

function readCandidates(
  value: unknown,
  range: { start_time: string; end_time: string },
): V9EngineCandidate[] {
  if (!Array.isArray(value) || value.length === 0) {
    throw new RectificationEngineError("engine_invalid_candidate_decisions", "engine candidate decisions are missing");
  }
  const seenIds = new Set<string>();
  const seenTimes = new Set<string>();
  const candidates: V9EngineCandidate[] = [];
  for (const item of value) {
    const row = record(item);
    const candidateId = row?.candidate_id;
    const time = row?.time;
    const rank = row?.rank;
    const relativeSupport = row?.relative_support;
    const tiedMinuteCount = row?.tied_minute_count;
    if (
      typeof candidateId !== "string" || !uuidPattern.test(candidateId)
      || typeof time !== "string" || !timePattern.test(time) || !timeInRange(time, range)
      || typeof rank !== "number" || !Number.isInteger(rank) || rank < 1
      || typeof relativeSupport !== "number" || !Number.isInteger(relativeSupport) || relativeSupport < 0 || relativeSupport > 100
      || typeof tiedMinuteCount !== "number" || !Number.isInteger(tiedMinuteCount) || tiedMinuteCount < 1
      || seenIds.has(candidateId) || seenTimes.has(time)
    ) {
      throw new RectificationEngineError("engine_invalid_candidate_decisions", "engine candidate decisions are invalid");
    }
    seenIds.add(candidateId);
    seenTimes.add(time);
    candidates.push({ candidateId, time, rank, relativeSupport, tiedMinuteCount });
  }
  return candidates;
}

type ParsedReceipt = Readonly<{
  raw: V9DecisionReceipt;
  eventContractVersion: string;
  policyVersion: string;
  selectionAllowed: boolean;
  confirmationAllowed: boolean;
  representativeCandidateId: string | null;
  representativeTime: string | null;
  overallConfidence: "low" | "medium" | "high";
  marginPercent: number | null;
}>;

function invalidReceipt(): never {
  throw new RectificationEngineError("engine_invalid_v2_receipt", "engine decision receipt is missing or invalid");
}

function readDecisionReceipt(value: unknown, candidates: readonly V9EngineCandidate[]): ParsedReceipt {
  const row = record(value);
  if (!row) return invalidReceipt();
  const representativeCandidateId = row.representative_candidate_id;
  const representativeTime = row.representative_time;
  const confidence = row.overall_confidence;
  const marginPercent = row.margin_percent === null || row.margin_percent === undefined
    ? null
    : engineNumber(row.margin_percent);
  if (
    row.receipt_version !== RECEIPT_VERSION
    || row.contract_version !== "v2"
    || row.event_contract_version !== EVENT_CONTRACT_VERSION
    || typeof row.policy_version !== "string" || !row.policy_version
    || typeof row.decision_policy_version !== "string" || row.decision_policy_version !== row.policy_version
    || typeof row.display_allowed !== "boolean"
    || typeof row.selection_allowed !== "boolean"
    || typeof row.acceptance_allowed !== "boolean"
    || typeof row.confirmation_allowed !== "boolean"
    || typeof row.accept_allowed !== "boolean"
    || typeof row.confirm_allowed !== "boolean"
    || row.selection_allowed !== row.acceptance_allowed
    || row.selection_allowed !== row.accept_allowed
    || row.confirmation_allowed !== row.confirm_allowed
    || (representativeCandidateId !== null && (typeof representativeCandidateId !== "string" || !uuidPattern.test(representativeCandidateId)))
    || (representativeTime !== null && (typeof representativeTime !== "string" || !timePattern.test(representativeTime)))
    || (confidence !== "low" && confidence !== "medium" && confidence !== "high")
    || (row.margin_percent !== null && row.margin_percent !== undefined && marginPercent === null)
  ) {
    return invalidReceipt();
  }
  const representative = representativeCandidateId === null
    ? null
    : candidates.find((candidate) => candidate.candidateId === representativeCandidateId) ?? null;
  if (
    (representativeCandidateId === null) !== (representativeTime === null)
    || (representativeCandidateId !== null && (!representative || representative.time !== representativeTime))
    || (row.confirmation_allowed === true && row.selection_allowed !== true)
    || (row.selection_allowed === true && row.display_allowed !== true)
  ) {
    return invalidReceipt();
  }
  return {
    raw: row,
    eventContractVersion: EVENT_CONTRACT_VERSION,
    policyVersion: row.policy_version,
    selectionAllowed: row.selection_allowed,
    confirmationAllowed: row.confirmation_allowed,
    representativeCandidateId,
    representativeTime,
    overallConfidence: confidence,
    marginPercent,
  };
}

function readExecutionLedger(version: unknown, value: unknown): V9ExecutionLedger {
  if (version !== EXECUTION_LEDGER_VERSION || !Array.isArray(value) || value.length === 0) {
    throw new RectificationEngineError("engine_invalid_execution_ledger", "engine execution ledger is missing or invalid");
  }
  return value.map((item) => {
    const row = record(item);
    if (
      !row
      || row.ledger_version !== EXECUTION_LEDGER_VERSION
      || typeof row.stage !== "string" || !row.stage
      || (row.status !== "executed" && row.status !== "not_executed" && row.status !== "retained_not_scored")
      || typeof row.source !== "string" || !row.source
    ) {
      throw new RectificationEngineError("engine_invalid_execution_ledger", "engine execution ledger is missing or invalid");
    }
    return row;
  });
}

function publicMethodFromLedger(value: unknown): PublicRectificationMethod | null {
  if (isPublicRectificationMethod(value)) return value;
  if (typeof value !== "string") return null;
  const normalized = value.toLowerCase();
  if (normalized.includes("controlled_transit") || normalized.includes("gochara")) return "gochara";
  if (normalized.includes("ashtakavarga")) return "ashtakavarga";
  if (normalized.includes("shadbala")) return "shadbala";
  if (normalized.includes("arudha")) return "arudha-pada";
  if (normalized.includes("functional_benefic") || normalized.includes("functional_malefic")) return "functional-benefic-malefic";
  if (normalized.includes("vimshottari") || normalized.includes("vimsottari")) return "vimshottari-dasha";
  if (normalized.includes("narayana")) return "narayana-dasha";
  return null;
}

function executedMethods(ledger: V9ExecutionLedger): PublicRectificationMethod[] {
  const methods = new Set<PublicRectificationMethod>();
  for (const entry of ledger) {
    if (entry.status !== "executed") continue;
    const direct = publicMethodFromLedger(entry.method);
    if (direct) methods.add(direct);
    if (Array.isArray(entry.technique_layers)) {
      for (const layer of entry.technique_layers) {
        const method = publicMethodFromLedger(layer);
        if (method) methods.add(method);
      }
    }
  }
  return [...methods];
}

function engineDiagnostics(data: Record<string, unknown>): Readonly<Record<string, unknown>> {
  return record(data.diagnostics) ?? {};
}

function engineRequestBody(input: {
  baselineBirthSnapshot: Readonly<Record<string, unknown>>;
  candidateRange: { start_time: string; end_time: string };
  events: readonly V9EngineEvent[];
}): Record<string, unknown> {
  const snapshot = input.baselineBirthSnapshot;
  const birthDate = String(snapshot.birth_date ?? "");
  const lat = engineNumber(snapshot.latitude);
  const lon = engineNumber(snapshot.longitude);
  const tz = engineNumber(snapshot.timezone_offset);
  if (!birthDate || lat === null || lon === null || tz === null) {
    throw new RectificationEngineError("engine_profile_incomplete", "server profile snapshot is incomplete");
  }
  if (input.events.length === 0) {
    throw new RectificationEngineError("no_scorable_evidence", "no scorable evidence for the engine");
  }
  return {
    birth_date: birthDate,
    start_time: input.candidateRange.start_time,
    end_time: input.candidateRange.end_time,
    lat,
    lon,
    tz,
    events: input.events,
    birth_time_source: snapshot.birth_time_source,
    timezone_id: snapshot.timezone_id,
    timezone_source: snapshot.timezone_source,
    local_time_status: snapshot.local_time_status,
  };
}

export async function runV9CandidateScore(input: {
  baselineBirthSnapshot: Readonly<Record<string, unknown>>;
  candidateRange: { start_time: string; end_time: string };
  events: readonly V9EngineEvent[];
}): Promise<V9EngineScoreResult> {
  const data = await postEngine("/api/rectification/v5/score", engineRequestBody(input));
  const candidates = readCandidates(data.candidate_decisions, input.candidateRange);
  const receipt = readDecisionReceipt(data.decision_receipt, candidates);
  const ledger = readExecutionLedger(data.execution_ledger_version, data.execution_ledger);
  if (
    data.event_contract_version !== receipt.eventContractVersion
    || data.decision_policy_version !== receipt.policyVersion
  ) {
    return invalidReceipt();
  }
  return {
    engineResultId: String(data.result_id ?? ""),
    algorithmVersion: String(data.algorithm_version ?? ""),
    eventContractVersion: receipt.eventContractVersion,
    policyVersion: receipt.policyVersion,
    candidateRange: input.candidateRange,
    candidates,
    overallConfidence: receipt.overallConfidence,
    marginPercent: receipt.marginPercent,
    selectionAllowed: receipt.selectionAllowed,
    confirmationAllowed: receipt.confirmationAllowed,
    representativeCandidateId: receipt.representativeCandidateId,
    representativeTime: receipt.representativeTime,
    decisionReceipt: receipt.raw,
    executionLedger: ledger,
    executedMethods: executedMethods(ledger),
  };
}

export async function runV9Diagnostics(input: {
  baselineBirthSnapshot: Readonly<Record<string, unknown>>;
  candidateRange: { start_time: string; end_time: string };
  events: readonly V9EngineEvent[];
}): Promise<V9EngineDiagnostics> {
  const data = await postEngine("/api/rectification/v5/diagnostics", engineRequestBody(input));
  const candidates = readCandidates(data.candidate_decisions, input.candidateRange);
  const receipt = readDecisionReceipt(data.decision_receipt, candidates);
  const ledger = readExecutionLedger(data.execution_ledger_version, data.execution_ledger);
  if (
    data.event_contract_version !== receipt.eventContractVersion
    || data.decision_policy_version !== receipt.policyVersion
  ) {
    return invalidReceipt();
  }
  const diagnostics = engineDiagnostics(data);
  const missingLayers = Array.isArray(data.missing_layers)
    ? data.missing_layers.filter((item): item is string => typeof item === "string")
    : [];
  return {
    algorithmVersion: String(data.algorithm_version ?? ""),
    engineResultId: String(data.result_id ?? ""),
    eventContractVersion: receipt.eventContractVersion,
    policyVersion: receipt.policyVersion,
    diagnostics: {
      primary_cluster_retention_rate: diagnostics.primary_cluster_retention_rate,
      leave_one_event_out_retention_rate: diagnostics.leave_one_event_out_retention_rate,
      leave_one_domain_out_retention_rate: diagnostics.leave_one_domain_out_retention_rate,
      date_sensitivity_retention_rate: diagnostics.date_sensitivity_retention_rate,
      neighbor_support_minutes: diagnostics.neighbor_support_minutes,
      primary_secondary_margin_percent: diagnostics.primary_secondary_margin_percent,
      unstable_event_ids: diagnostics.unstable_event_ids,
      most_discriminating_layers: diagnostics.most_discriminating_layers,
      candidate_splits: diagnostics.candidate_splits,
    },
    missingLayers,
    canConfirmExactMinute: receipt.confirmationAllowed,
    decisionReceipt: receipt.raw,
    executionLedger: ledger,
    executedMethods: executedMethods(ledger),
  };
}

export const v9EngineVersion = (): string =>
  process.env.RECTIFICATION_ENGINE_VERSION?.trim() || "rectification-v5";