/**
 * V9 deterministic engine client (Python, server-side only).
 *
 * Builds engine payloads exclusively from the Case's baseline birth snapshot
 * and the durable evidence ledger. The model never supplies birth data,
 * candidate ranges or event arrays. Responses are compacted to safe,
 * allowlisted projections before they reach the tool layer.
 *
 * Contract notes (verified against scripts/jyotish_api_server.py +
 * scripts/rectification/api_service.py):
 *   * The engine's SCOREABLE_EVENT_KINDS is a coarse vocabulary
 *     (education_milestone / relocation / relationship_start|change /
 *     career_change / finance_change / self_health_event under
 *     health_pressure). V9 evidence kinds are mapped onto that vocabulary;
 *     non-scoreable kinds (family_event, other) stay in the ledger but never
 *     reach the engine.
 *   * /api/rectification/v5/score returns candidate_scores as
 *     [{time, score, supporting_event_ids, conflicting_event_ids}] without
 *     rank/tied/representative/confidence fields. Rank and tie counts are
 *     derived deterministically here; relative support is normalized from
 *     scores; representative time is the top-ranked candidate; the
 *     confirmation gate is bound to the engine's own can_confirm_exact_minute.
 */

import 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;
}>;

export type V9EngineCandidate = Readonly<{
  rank: number;
  time: string;
  relative_support: number;
  tied_minute_count: number;
}>;

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

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

const timePattern = /^(?:[01]\d|2[0-3]):[0-5]\d$/;

const DOMAIN_METHODS: Readonly<Record<string, readonly PublicRectificationMethod[]>> = {
  education: ["d24-chaturvimshamsha"],
  relocation: ["d4-chaturthamsha"],
  relationship: ["d9-navamsa"],
  career: ["d10-dashamsa"],
  finance: ["d2-hora", "d11-labhamsha"],
  health_pressure: ["d30-trimshamsha"],
};

function techniqueLayers(value: unknown): string[] {
  if (!value || typeof value !== "object") return [];
  return Object.values(value as Record<string, unknown>).flatMap((eventRows) => {
    if (!eventRows || typeof eventRows !== "object") return [];
    return Object.values(eventRows as Record<string, unknown>).flatMap((candidate) => {
      if (!candidate || typeof candidate !== "object") return [];
      const layers = (candidate as Record<string, unknown>).technique_layers;
      return Array.isArray(layers) ? layers.filter((item): item is string => typeof item === "string") : [];
    });
  });
}

function executedMethods(
  events: readonly V9EngineEvent[],
  layers: readonly string[],
): PublicRectificationMethod[] {
  const methods = new Set<PublicRectificationMethod>([
    "d1-rashi",
    "vimshottari-dasha",
    "narayana-dasha",
  ]);
  for (const event of events) {
    for (const method of DOMAIN_METHODS[event.domain] ?? []) methods.add(method);
  }
  const normalized = layers.map((layer) => layer.toLowerCase());
  if (normalized.some((layer) => layer.includes("controlled_transit") || layer.includes("gochara"))) methods.add("gochara");
  if (normalized.some((layer) => layer.includes("ashtakavarga"))) methods.add("ashtakavarga");
  if (normalized.some((layer) => layer.includes("shadbala"))) methods.add("shadbala");
  if (normalized.some((layer) => layer.includes("arudha"))) methods.add("arudha-pada");
  if (normalized.some((layer) => layer.includes("functional_benefic") || layer.includes("functional_malefic"))) {
    methods.add("functional-benefic-malefic");
  }
  return [...methods];
}

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;
}

/**
 * The engine's scoreable (domain, kind) vocabulary (contracts.py
 * SCOREABLE_EVENT_KINDS). V9 evidence kinds are mapped kind-aware so
 * relationship_start/change keep their distinct engine semantics. Rows that
 * map to null (family/other or unknown domains) are excluded from scoring;
 * they remain evidence in the ledger.
 */
export function toEngineScoreableEvent(
  item: Readonly<{
    eventKind: string;
    domain: string;
  }>,
): { domain: string; event_kind: string } | null {
  const kind = item.eventKind;
  switch (item.domain) {
    case "education":
      return { domain: "education", event_kind: "education_milestone" };
    case "career":
      return { domain: "career", event_kind: "career_change" };
    case "relationship":
      if (kind === "relationship_start" || kind === "relationship_commitment") {
        return { domain: "relationship", event_kind: "relationship_start" };
      }
      return { domain: "relationship", event_kind: "relationship_change" };
    case "relocation":
      return { domain: "relocation", event_kind: "relocation" };
    case "finance":
      return { domain: "finance", event_kind: "finance_change" };
    case "health":
      return { domain: "health_pressure", event_kind: "self_health_event" };
    default:
      // family, other and unknown domains are background evidence only.
      return null;
  }
}

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

export function toEngineEvents(
  evidence: readonly Readonly<{
    id: string;
    eventKind: string;
    domain: string;
    occurredFrom: string | null;
    occurredTo: string | null;
    datePrecision: string;
    summary: string;
  }>[],
): V9EngineEvent[] {
  return evidence.flatMap((item): V9EngineEvent[] => {
    const scoreable = toEngineScoreableEvent(item);
    if (!scoreable) return [];
    const start = item.occurredFrom ?? item.occurredTo;
    const end = item.occurredTo ?? item.occurredFrom;
    if (!start) return [];
    return [{
      id: item.id,
      domain: scoreable.domain,
      event_kind: scoreable.event_kind,
      date_start: start.slice(0, 10),
      date_end: end ? end.slice(0, 10) : start.slice(0, 10),
      precision: enginePrecision(item.datePrecision),
      summary: item.summary,
    }];
  });
}

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?.error || data?.message || `Jyotish API ${path} returned ${response.status}`;
    throw new RectificationEngineError("engine_http_error", String(message));
  }
  if (!data || typeof data !== "object") {
    throw new RectificationEngineError("engine_invalid_response", `Jyotish API ${path} returned an invalid response`);
  }
  return data as Record<string, unknown>;
}

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

/**
 * Derive ranked candidates from the engine's [{time, score}] rows. The engine
 * does not rank; rank = score-descending order and tied_minute_count = how
 * many candidate minutes in the scan share the same score.
 */
function readCandidates(value: unknown, range: { start_time: string; end_time: string }): V9EngineCandidate[] {
  if (!Array.isArray(value)) return [];
  const scored = value.flatMap((item): Array<{ time: string; score: number }> => {
    if (!item || typeof item !== "object") return [];
    const row = item as Record<string, unknown>;
    const time = typeof row.time === "string" ? row.time : "";
    const score = typeof row.score === "number" && Number.isFinite(row.score) ? row.score : 0;
    if (!timePattern.test(time) || !timeInRange(time, range)) return [];
    return [{ time, score }];
  });
  if (scored.length === 0) return [];
  scored.sort((left, right) => right.score - left.score);
  const top = scored.slice(0, 3);
  const weights = top.map((row) => Math.max(0, row.score));
  const total = weights.reduce((sum, weight) => sum + weight, 0);
  const supports = weights.map((weight) => total > 0 ? Math.round((weight / total) * 100) : Math.floor(100 / top.length));
  supports[0] += 100 - supports.reduce((sum, support) => sum + support, 0);
  return top.map((row, index) => ({
    rank: index + 1,
    time: row.time,
    relative_support: supports[index] ?? 0,
    tied_minute_count: scored.filter((candidate) => candidate.score === row.score).length,
  }));
}

function engineDiagnostics(data: Record<string, unknown>): Record<string, unknown> {
  return data.diagnostics && typeof data.diagnostics === "object"
    ? data.diagnostics as Record<string, unknown>
    : {};
}

export async function runV9CandidateScore(input: {
  baselineBirthSnapshot: Readonly<Record<string, unknown>>;
  candidateRange: { start_time: string; end_time: string };
  events: readonly V9EngineEvent[];
}): Promise<V9EngineScoreResult> {
  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");
  }
  const data = await postEngine("/api/rectification/v5/score", {
    birth_date: birthDate,
    start_time: input.candidateRange.start_time,
    end_time: input.candidateRange.end_time,
    lat,
    lon,
    tz,
    events: input.events,
  });
  const candidates = readCandidates(data.candidate_scores, input.candidateRange);
  if (candidates.length === 0) {
    throw new RectificationEngineError("engine_no_candidates", "the engine returned no usable candidates");
  }
  const diagnostics = engineDiagnostics(data);
  const methods = executedMethods(input.events, techniqueLayers(data.event_contribution_matrix));
  const marginPercent = engineNumber(diagnostics.primary_secondary_margin_percent)
    ?? engineNumber(data.margin_percent)
    ?? null;
  const retention = engineNumber(diagnostics.leave_one_event_out_retention_rate);
  const confidence: "low" | "medium" | "high" =
    marginPercent !== null && marginPercent >= 40 && retention !== null && retention >= 0.8
      ? "high"
      : marginPercent !== null && marginPercent >= 20
        ? "medium"
        : data.confidence === "high" || data.confidence === "medium"
          ? data.confidence
          : "low";
  return {
    engineResultId: String(data.result_id ?? ""),
    algorithmVersion: String(data.algorithm_version ?? "rectification-v5"),
    candidateRange: input.candidateRange,
    candidates,
    overallConfidence: confidence,
    marginPercent,
    selectionAllowed: candidates.length > 0,
    confirmationAllowed: data.can_confirm_exact_minute === true,
    representativeTime: candidates[0]?.time ?? null,
    executedMethods: methods,
  };
}

export async function runV9Diagnostics(input: {
  baselineBirthSnapshot: Readonly<Record<string, unknown>>;
  candidateRange: { start_time: string; end_time: string };
  events: readonly V9EngineEvent[];
}): Promise<V9EngineDiagnostics> {
  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");
  }
  const data = await postEngine("/api/rectification/v5/diagnostics", {
    birth_date: birthDate,
    start_time: input.candidateRange.start_time,
    end_time: input.candidateRange.end_time,
    lat,
    lon,
    tz,
    events: input.events,
  });
  const diagnostics = engineDiagnostics(data);
  const missingLayers = Array.isArray(data.missing_layers) ? data.missing_layers as string[] : [];
  const discriminatingLayers = Array.isArray(diagnostics.most_discriminating_layers)
    ? diagnostics.most_discriminating_layers.filter((item): item is string => typeof item === "string")
    : [];
  return {
    algorithmVersion: String(data.algorithm_version ?? "rectification-v5"),
    engineResultId: String(data.result_id ?? ""),
    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: data.can_confirm_exact_minute === true,
    executedMethods: executedMethods(input.events, discriminatingLayers),
  };
}

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