import { createStore } from 'zustand/vanilla'

export interface KeyStats {
  /** Total times trigger() was called for this key. */
  triggerCount: number
  /** Calls absorbed by the throttle window (same payload, returned existing promise). */
  throttledCount: number
  /** Concurrent in-flight calls deduplicated (same key+params already running). */
  dedupedCount: number
  /** Calls skipped by the shouldFetch predicate — no I/O, no events. */
  shouldFetchSkipCount: number
  /** Native cache hits — data served from the native store without an API call. */
  cacheHitCount: number
  /** Actual API calls initiated (queryFn executed). */
  apiFetchCount: number
  /** Pipeline errors (any phase: fetch, validate, transform, write). */
  errorCount: number
}

export type StatsState = Record<string, KeyStats>

export function defaultKeyStats(): KeyStats {
  return {
    triggerCount: 0,
    throttledCount: 0,
    dedupedCount: 0,
    shouldFetchSkipCount: 0,
    cacheHitCount: 0,
    apiFetchCount: 0,
    errorCount: 0,
  }
}

export function createStatsStore() {
  return createStore<StatsState>(() => ({}))
}

export type StatsStore = ReturnType<typeof createStatsStore>

export function incrementStat(
  store: StatsStore,
  key: string,
  field: keyof KeyStats,
): void {
  store.setState((state) => ({
    [key]: {
      ...(state[key] ?? defaultKeyStats()),
      [field]: (state[key]?.[field] ?? 0) + 1,
    },
  }))
}