const API_BASE = '/api/v1';

function getAuthHeaders(): Record<string, string> {
  const token = localStorage.getItem('fraudshield_token');
  const headers: Record<string, string> = { 'Content-Type': 'application/json' };
  if (token) headers['Authorization'] = `Bearer ${token}`;
  return headers;
}

async function apiFetch<T>(path: string, options: RequestInit = {}): Promise<T> {
  const res = await fetch(`${API_BASE}${path}`, {
    ...options,
    headers: { ...getAuthHeaders(), ...((options.headers as Record<string, string>) || {}) },
  });
  if (!res.ok) {
    const err = await res.json().catch(() => ({ detail: res.statusText }));
    throw new Error(err.detail || `HTTP ${res.status}`);
  }
  return res.json();
}

export interface AlertFilters {
  status?: string;
  min_score?: number;
  from_date?: string;
  to_date?: string;
  triggered_rule?: string;
  limit?: number;
  offset?: number;
}

export interface TriggeredRule {
  rule_id: string;
  rule_name: string;
  score: number;
  explanation: string;
}

export interface AlertSummary {
  id: string;
  score: number;
  status: string;
  amount: number;
  merchant_name: string;
  top_rule: string;
  created_at: string;
}

export interface AlertDetail {
  id: string;
  transaction_id: string;
  score: number;
  triggered_rules: TriggeredRule[];
  explanation: string;
  status: string;
  assigned_to?: string | null;
  decision?: string | null;
  decided_by?: string | null;
  decided_at?: string | null;
  justification?: string | null;
  created_at: string;
  amount: number;
  merchant_name: string;
  merchant_category: string;
  channel: string;
}

export interface AlertListResponse {
  items: AlertSummary[];
  total: number;
  limit: number;
  offset: number;
}

export interface AlertDecisionRequest {
  decision: string;
  justification?: string;
  notes?: string;
}

export interface TransactionAccepted {
  transaction_id: string;
  status: string;
  trace_id: string;
}

export interface DashboardMetrics {
  period: string;
  total_transactions: number;
  total_alerts: number;
  fraud_rate_pct: number;
  false_positive_rate_pct: number;
  alerts_by_status: { pending: number; confirmed: number; false_positive: number; escalated: number };
  alerts_by_hour: { hour: number; count: number }[];
  top_triggering_rules: { rule_name: string; alert_count: number }[];
  score_distribution: { low: number; medium: number; high: number; critical: number };
}

export interface DetectionRule {
  id: string;
  name: string;
  description: string;
  condition: string;
  weight: number;
  threshold: number;
  is_active: boolean;
  version: number;
  created_by: string;
  created_at: string;
  updated_at: string;
}

export function listAlerts(params: AlertFilters = {}): Promise<AlertListResponse> {
  const qs = new URLSearchParams();
  Object.entries(params).forEach(([k, v]) => { if (v !== undefined) qs.set(k, String(v)); });
  return apiFetch<AlertListResponse>(`/alerts?${qs.toString()}`);
}

export function getAlert(id: string): Promise<AlertDetail> {
  return apiFetch<AlertDetail>(`/alerts/${id}`);
}

export function decideAlert(id: string, data: AlertDecisionRequest): Promise<AlertDetail> {
  return apiFetch<AlertDetail>(`/alerts/${id}/decide`, { method: 'POST', body: JSON.stringify(data) });
}

export function getDashboardMetrics(period = '24h'): Promise<DashboardMetrics> {
  return apiFetch<DashboardMetrics>(`/dashboard/metrics?period=${period}`);
}

export { getAuthHeaders };