apophis-fastify/src/infrastructure/outbound-mock-runtime.ts

/**
 * Outbound Mock Runtime — Stateful
 *
 * Installs a temporary fetch patch during test execution.
 * Records outbound calls and returns generated or overridden responses.
 *
 * STATEFUL BEHAVIOR:
 * - Resource model: POST creates entities, GET/PATCH/DELETE operate on them
 * - Contract-driven: uses route's x-ensures to constrain responses
 * - Request-to-response: copies request fields to response per x-mock templates
 * - Call history: previous calls influence subsequent responses
 */
import { convertSchema } from '../domain/schema-to-arbitrary.js'
import { SeededRng } from '../infrastructure/seeded-rng.js'
import { matchesTarget } from './wildcard-match.js'
import type { OutboundCallRecord, ResolvedOutboundContract } from '../types.js'
import * as fc from 'fast-check'

export interface OutboundMockRuntime {
  install(): void
  restore(): void
  getCalls(name?: string): ReadonlyArray<OutboundCallRecord>
  /** Get stored resource by contract name and ID */
  getResource(contractName: string, id: string): unknown | undefined
  /** Clear all stored resources and call history */
  clear(): void
  /** Inject a specific response for the next call to a contract (for property testing) */
  injectResponse(contractName: string, statusCode: number, body: unknown): void
}
export interface OutboundMockOptions {
  readonly contracts: ResolvedOutboundContract[]
  readonly mode: 'example' | 'property'
  readonly overrides?: Record<string, {
    readonly forceStatus?: number
    readonly headers?: Record<string, string>
    readonly body?: unknown
  }>
  readonly unmatched: 'error' | 'passthrough'
  readonly seed: number
  /** Route-level behavioral contracts to constrain mock responses */
  readonly routeEnsures?: readonly string[]
  /** Runtime identifier for diagnostics */
  readonly runtimeId?: string
}

let activeRuntimeId: string | undefined

export function getActiveMockRuntimeId(): string | undefined {
  return activeRuntimeId
}
/** Resource store: contractName → resourceId → resourceBody */
type ResourceStore = Map<string, Map<string, unknown>>
export function createOutboundMockRuntime(opts: OutboundMockOptions): OutboundMockRuntime {
  const calls: OutboundCallRecord[] = []
  let originalFetch: typeof globalThis.fetch | undefined
  const rng = new SeededRng(opts.seed)
  const resources: ResourceStore = new Map()
  /** Injected responses for property testing: contractName → {statusCode, body} */
  const injectedResponses = new Map<string, { statusCode: number; body: unknown }>()
  const getOrCreateResourceStore = (contractName: string): Map<string, unknown> => {
    let store = resources.get(contractName)
    if (!store) {
      store = new Map()
      resources.set(contractName, store)
    }
    return store
  }
  const extractIdFromUrl = (url: string, pattern?: string): string | undefined => {
    if (!pattern) {
      // Default: last path segment
      const segments = url.split('/')
      return segments[segments.length - 1]
    }
    // Simple pattern matching: /v1/payment_intents/:id
    const regexPattern = pattern.replace(/:id/g, '([^/]+)')
    const match = url.match(new RegExp(regexPattern))
    return match?.[1]
  }
  const generateResponseBody = (
    contract: ResolvedOutboundContract,
    statusCode: number,
    requestBody: unknown,
    requestUrl: string
  ): unknown => {
    const schema = contract.response[statusCode]
    if (!schema) return null
    // Generate base response from schema
    const arb = convertSchema(schema, { context: 'response' })
    const samples = fc.sample(arb, { numRuns: 1, seed: opts.seed + calls.length })
    let body = samples[0] ?? null
    if (typeof body !== 'object' || body === null) return body
    // Apply request-to-response field copying from contract ensures
    if (contract.ensures) {
      for (const ensure of contract.ensures) {
        // Parse simple request_body.field == response_body.field patterns
        const match = ensure.match(/request_body\.([a-zA-Z_][a-zA-Z0-9_]*)\s*==\s*response_body\.([a-zA-Z_][a-zA-Z0-9_]*)/)
        if (match) {
          const requestField = match[1]!
          const responseField = match[2]!
          const reqBody = requestBody as Record<string, unknown> | undefined
          if (reqBody && requestField in reqBody) {
            ;(body as Record<string, unknown>)[responseField] = reqBody[requestField]
          }
        }
      }
    }
    // Apply route-level ensures (higher priority)
    if (opts.routeEnsures) {
      for (const ensure of opts.routeEnsures) {
        // Parse response_body.field == value constraints
        const match = ensure.match(/response_body\.([a-zA-Z_][a-zA-Z0-9_]*)\s*==\s*(.+)/)
        if (match) {
          const field = match[1]!
          const valueStr = match[2]!.trim()
          // Parse literal values
          let value: unknown
          if (valueStr === 'true') value = true
          else if (valueStr === 'false') value = false
          else if (valueStr === 'null') value = null
          else if (!isNaN(Number(valueStr))) value = Number(valueStr)
          else if (valueStr.startsWith('"') && valueStr.endsWith('"')) value = valueStr.slice(1, -1)
          else continue
          ;(body as Record<string, unknown>)[field] = value
        }
      }
    }
    return body
  }
  const handleResourceLifecycle = (
    contract: ResolvedOutboundContract,
    method: string,
    url: string,
    requestBody: unknown,
    generatedBody: unknown
  ): { statusCode: number; body: unknown } => {
    if (!contract.resource) {
      return { statusCode: 200, body: generatedBody }
    }
    const store = getOrCreateResourceStore(contract.name)
    const createMethods = contract.resource.createMethods ?? ['POST']
    const readMethods = contract.resource.readMethods ?? ['GET']
    const updateMethods = contract.resource.updateMethods ?? ['PATCH', 'PUT']
    const deleteMethods = contract.resource.deleteMethods ?? ['DELETE']
    if (createMethods.includes(method)) {
      // Create resource
      const idField = contract.resource.idField
      const body = generatedBody as Record<string, unknown>
      const id = body[idField] as string | undefined
      if (id) {
        store.set(id, body)
      }
      return { statusCode: 201, body }
    }
    if (readMethods.includes(method)) {
      // Read resource
      const id = extractIdFromUrl(url, contract.resource.idPattern)
      if (id && store.has(id)) {
        return { statusCode: 200, body: store.get(id) }
      }
      return { statusCode: 404, body: { error: { type: 'invalid_request_error', message: `Resource not found: ${id}` } } }
    }
    if (updateMethods.includes(method)) {
      // Update resource
      const id = extractIdFromUrl(url, contract.resource.idPattern)
      if (id && store.has(id)) {
        const existing = store.get(id) as Record<string, unknown>
        const updates = requestBody as Record<string, unknown> ?? {}
        const merged = { ...existing, ...updates }
        store.set(id, merged)
        return { statusCode: 200, body: merged }
      }
      return { statusCode: 404, body: { error: { type: 'invalid_request_error', message: `Resource not found: ${id}` } } }
    }
    if (deleteMethods.includes(method)) {
      // Delete resource
      const id = extractIdFromUrl(url, contract.resource.idPattern)
      if (id && store.has(id)) {
        store.delete(id)
        return { statusCode: 200, body: { deleted: true, id } }
      }
      return { statusCode: 404, body: { error: { type: 'invalid_request_error', message: `Resource not found: ${id}` } } }
    }
    return { statusCode: 200, body: generatedBody }
  }
  const install = (): void => {
    if (activeRuntimeId !== undefined) {
      throw new Error(
        `OutboundMockRuntime already active (owner: ${activeRuntimeId}). ` +
        'Only one outbound mock runtime can be installed at a time. ' +
        'Restore the existing runtime first. ' +
        'Consider running mock-dependent tests serially.'
      )
    }
    if (originalFetch !== undefined) {
      throw new Error('OutboundMockRuntime already installed')
    }
    if (opts.runtimeId) {
      activeRuntimeId = opts.runtimeId
    }
    originalFetch = globalThis.fetch
    globalThis.fetch = async (input: RequestInfo | URL, init?: RequestInit) => {
      const url = typeof input === 'string' ? input : input instanceof URL ? input.href : input.url
      const method = init?.method ?? 'GET'
      // Find matching contract (allow method wildcard '*' for resource contracts)
      const contract = opts.contracts.find((c) => matchesTarget(url, c.target) && (c.method === method || c.method === '*'))
      if (!contract) {
        if (opts.unmatched === 'error') {
          throw new Error(
            `Unmatched outbound request: ${method} ${url}. ` +
              `No contract declared for this dependency. ` +
              `Add it to x-outbound or set outboundMocks.unmatched to 'passthrough'.`
          )
        }
        return originalFetch!(input, init)
      }
      // Check for override
      const override = opts.overrides?.[contract.name]
      let statusCode: number
      let headers: Record<string, string>
      let body: unknown
      // Check for injected response (highest priority - used for property testing)
      const injected = injectedResponses.get(contract.name)
      if (injected) {
        injectedResponses.delete(contract.name)
        statusCode = injected.statusCode
        headers = { 'content-type': 'application/json' }
        body = injected.body
      } else if (override) {
        statusCode = override.forceStatus ?? 200
        headers = override.headers ?? { 'content-type': 'application/json' }
        body = override.body ?? null
      } else {
        // Parse request body
        let requestBody: unknown
        if (init?.body) {
          try {
            requestBody = typeof init.body === 'string' ? JSON.parse(init.body) : init.body
          } catch {
            requestBody = init.body
          }
        }
        // Pick status code deterministically
        const statuses = Object.keys(contract.response).map(Number)
        const statusIndex = statuses.length > 0 ? Math.floor(rng.next() * statuses.length) : 0
        const pickedStatus = statuses[statusIndex] ?? 200
        // Generate response body with context awareness
        const generatedBody = generateResponseBody(contract, pickedStatus, requestBody, url)
        // Handle resource lifecycle (CRUD)
        const result = handleResourceLifecycle(contract, method, url, requestBody, generatedBody)
        statusCode = result.statusCode
        body = result.body
        headers = { 'content-type': 'application/json' }
      }
      // Record the call
      let requestBody: unknown
      if (init?.body) {
        try {
          requestBody = typeof init.body === 'string' ? JSON.parse(init.body) : init.body
        } catch {
          requestBody = init.body
        }
      }
      calls.push({
        name: contract.name,
        url,
        method,
        requestBody,
        responseStatus: statusCode,
        responseHeaders: headers,
        responseBody: body,
        timestamp: Date.now(),
      })
      const bodyString = body === null || body === undefined ? '' : typeof body === 'string' ? body : JSON.stringify(body)
      return new Response(bodyString, { status: statusCode, headers })
    }
  }
  const restore = (): void => {
    if (originalFetch !== undefined) {
      globalThis.fetch = originalFetch
      originalFetch = undefined
    }
    if (opts.runtimeId && activeRuntimeId === opts.runtimeId) {
      activeRuntimeId = undefined
    }
  }
  const getCalls = (name?: string): ReadonlyArray<OutboundCallRecord> => {
    if (name === undefined) return calls
    return calls.filter((c) => c.name === name)
  }
  const getResource = (contractName: string, id: string): unknown | undefined => {
    return resources.get(contractName)?.get(id)
  }
  const clear = (): void => {
    calls.length = 0
    resources.clear()
  }
  const injectResponse = (contractName: string, statusCode: number, body: unknown): void => {
    injectedResponses.set(contractName, { statusCode, body })
  }
  return { install, restore, getCalls, getResource, clear, injectResponse }
}