import { randomUUID } from 'node:crypto'

import type { Session, WebContents } from 'electron/main'
import { app } from 'electron/main'

import type {
  DesktopObservedRequest,
  DesktopObservedRequestKind,
  DesktopObservedRequestSnapshot,
  DesktopObservedRequestSource,
} from '../shared/network-debug'

interface ActiveObservedRequest {
  id: string
  startedAt: number
  kind: DesktopObservedRequestKind
  source: DesktopObservedRequestSource
  label: string
  method: string
  url: string
  partition: string | null
  resourceType: string | null
}

interface StartObservedRequestOptions {
  kind?: DesktopObservedRequestKind
  source?: DesktopObservedRequestSource
  label: string
  method?: string
  url: string
  partition?: string | null
  resourceType?: string | null
}

const observedSessions = new WeakSet<Session>()
const activeRequests = new Map<string, ActiveObservedRequest>()
const observedRecords: DesktopObservedRequest[] = []
const maxObservedRecords = 240
const requestFilter = {
  urls: ['http://*/*', 'https://*/*', 'ws://*/*', 'wss://*/*'],
}
const redactedQueryKeys = /token|signature|sig|auth|key|password|session/i
const networkObserverEnabled = !app.isPackaged

let rendererTarget: WebContents | null = null
let originalFetch: typeof globalThis.fetch | null = null

export function installObservedGlobalFetch(): void {
  if (!networkObserverEnabled) {
    return
  }

  if (originalFetch || typeof globalThis.fetch !== 'function') {
    return
  }

  originalFetch = globalThis.fetch.bind(globalThis)
  globalThis.fetch = (async (input: RequestInfo | URL, init?: RequestInit) => {
    const url = requestURL(input)
    if (!url || !isInspectableURL(url) || !originalFetch) {
      return originalFetch!(input, init)
    }

    const method = requestMethod(input, init)
    const requestId = startObservedRequest({
      kind: inferKindFromHeaders(input, init),
      source: 'main',
      label: 'main.fetch',
      method,
      url,
    })

    try {
      const response = await originalFetch(input, init)
      resolveObservedRequest(requestId, {
        phase: 'response',
        status: response.status,
      })
      return response
    } catch (error) {
      failObservedRequest(requestId, error)
      throw error
    }
  }) as typeof globalThis.fetch
}

export function registerObservedRequestRendererTarget(webContents: WebContents): void {
  if (!networkObserverEnabled) {
    return
  }

  rendererTarget = webContents
  webContents.once('destroyed', () => {
    if (rendererTarget === webContents) {
      rendererTarget = null
    }
  })
}

export function observeSessionRequests(
  target: Session,
  options: { label: string; partition?: string | null },
): void {
  if (!networkObserverEnabled) {
    return
  }

  if (observedSessions.has(target)) {
    return
  }
  observedSessions.add(target)

  target.webRequest.onBeforeRequest(requestFilter, (details, callback) => {
    if (!isInspectableURL(details.url)) {
      callback({})
      return
    }

    const requestId = sessionRequestId(details.id, options.partition ?? null)
    activeRequests.set(requestId, {
      id: requestId,
      startedAt: Date.now(),
      kind: details.resourceType === 'webSocket' ? 'ws' : 'http',
      source: 'session',
      label: options.label,
      method: normalizeMethod(details.method),
      url: sanitizeURL(details.url),
      partition: options.partition ?? null,
      resourceType: normalizeResourceType(details.resourceType),
    })

    pushRecord(
      buildRecord(activeRequests.get(requestId)!, {
        at: Date.now(),
        phase: 'request',
      }),
    )

    callback({})
  })

  target.webRequest.onCompleted(requestFilter, (details) => {
    if (!isInspectableURL(details.url)) {
      return
    }

    const requestId = sessionRequestId(details.id, options.partition ?? null)
    const active =
      activeRequests.get(requestId) ??
      createFallbackActiveRequest(requestId, {
        source: 'session',
        label: options.label,
        method: normalizeMethod(details.method),
        url: details.url,
        partition: options.partition ?? null,
        resourceType: normalizeResourceType(details.resourceType),
      })

    pushRecord(
      buildRecord(active, {
        at: Date.now(),
        phase: 'response',
        status: details.statusCode,
        durationMs: Date.now() - active.startedAt,
      }),
    )
    activeRequests.delete(requestId)
  })

  target.webRequest.onErrorOccurred(requestFilter, (details) => {
    if (!isInspectableURL(details.url)) {
      return
    }

    const requestId = sessionRequestId(details.id, options.partition ?? null)
    const active =
      activeRequests.get(requestId) ??
      createFallbackActiveRequest(requestId, {
        source: 'session',
        label: options.label,
        method: normalizeMethod(details.method),
        url: details.url,
        partition: options.partition ?? null,
        resourceType: normalizeResourceType(details.resourceType),
      })

    pushRecord(
      buildRecord(active, {
        at: Date.now(),
        phase: 'error',
        durationMs: Date.now() - active.startedAt,
        error: normalizeErrorMessage(details.error),
      }),
    )
    activeRequests.delete(requestId)
  })
}

export function startObservedRequest(options: StartObservedRequestOptions): string {
  if (!networkObserverEnabled) {
    return ''
  }

  const id = `main:${randomUUID()}`
  const active: ActiveObservedRequest = {
    id,
    startedAt: Date.now(),
    kind: options.kind ?? 'http',
    source: options.source ?? 'main',
    label: options.label,
    method: normalizeMethod(options.method),
    url: sanitizeURL(options.url),
    partition: options.partition ?? null,
    resourceType: options.resourceType ?? null,
  }

  activeRequests.set(id, active)
  pushRecord(
    buildRecord(active, {
      at: active.startedAt,
      phase: 'request',
    }),
  )
  return id
}

export function resolveObservedRequest(
  id: string,
  options: {
    phase?: 'response' | 'close'
    status?: number | null
    error?: string | null
    keepActive?: boolean
  } = {},
): void {
  const active = activeRequests.get(id)
  if (!active) {
    return
  }

  pushRecord(
    buildRecord(active, {
      at: Date.now(),
      phase: options.phase ?? 'response',
      status: options.status ?? null,
      durationMs: Date.now() - active.startedAt,
      error: options.error ?? null,
    }),
  )

  if (!options.keepActive) {
    activeRequests.delete(id)
  }
}

export function failObservedRequest(id: string, error: unknown): void {
  const active = activeRequests.get(id)
  if (!active) {
    return
  }

  pushRecord(
    buildRecord(active, {
      at: Date.now(),
      phase: 'error',
      durationMs: Date.now() - active.startedAt,
      error: normalizeErrorMessage(error),
    }),
  )
  activeRequests.delete(id)
}

export function getObservedRequestSnapshot(): DesktopObservedRequestSnapshot {
  if (!networkObserverEnabled) {
    return {
      rendererAttached: false,
      activeCount: 0,
      recent: [],
    }
  }

  return {
    rendererAttached: Boolean(rendererTarget && !rendererTarget.isDestroyed()),
    activeCount: activeRequests.size,
    recent: observedRecords.slice(-80),
  }
}

function requestURL(input: RequestInfo | URL): string | null {
  if (typeof input === 'string') {
    return input
  }
  if (input instanceof URL) {
    return input.toString()
  }
  return typeof input.url === 'string' ? input.url : null
}

function requestMethod(input: RequestInfo | URL, init?: RequestInit): string {
  if (init?.method) {
    return normalizeMethod(init.method)
  }
  if (typeof Request !== 'undefined' && input instanceof Request) {
    return normalizeMethod(input.method)
  }
  return 'GET'
}

function inferKindFromHeaders(
  input: RequestInfo | URL,
  init?: RequestInit,
): DesktopObservedRequestKind {
  const headers = new Headers(init?.headers)
  if (!headers.has('accept') && typeof Request !== 'undefined' && input instanceof Request) {
    const requestAccept = input.headers.get('accept')
    if (requestAccept) {
      headers.set('accept', requestAccept)
    }
  }

  const accept = headers.get('accept')?.toLowerCase() ?? ''
  if (accept.includes('text/event-stream')) {
    return 'sse'
  }
  return 'http'
}

function isInspectableURL(url: string): boolean {
  try {
    const protocol = new URL(url).protocol
    return (
      protocol === 'http:' || protocol === 'https:' || protocol === 'ws:' || protocol === 'wss:'
    )
  } catch {
    return false
  }
}

function sanitizeURL(url: string): string {
  try {
    const parsed = new URL(url)
    for (const key of parsed.searchParams.keys()) {
      if (redactedQueryKeys.test(key)) {
        parsed.searchParams.set(key, '[REDACTED]')
      }
    }
    return parsed.toString()
  } catch {
    return url
  }
}

function normalizeMethod(value: string | undefined | null): string {
  return typeof value === 'string' && value.trim() ? value.trim().toUpperCase() : 'GET'
}

function normalizeResourceType(value: unknown): string | null {
  return typeof value === 'string' && value.trim() ? value : null
}

function normalizeErrorMessage(error: unknown): string {
  if (typeof error === 'string' && error.trim()) {
    return error
  }
  if (error instanceof Error) {
    return error.message || error.name || 'request_failed'
  }
  if (error && typeof error === 'object' && 'message' in error) {
    const message = (error as { message?: unknown }).message
    if (typeof message === 'string' && message.trim()) {
      return message
    }
  }
  return 'request_failed'
}

function sessionRequestId(id: number, partition: string | null): string {
  return `session:${partition ?? 'default'}:${id}`
}

function createFallbackActiveRequest(
  id: string,
  options: {
    source: DesktopObservedRequestSource
    label: string
    method?: string
    url: string
    partition?: string | null
    resourceType?: string | null
  },
): ActiveObservedRequest {
  return {
    id,
    startedAt: Date.now(),
    kind: options.resourceType === 'webSocket' ? 'ws' : 'http',
    source: options.source,
    label: options.label,
    method: normalizeMethod(options.method),
    url: sanitizeURL(options.url),
    partition: options.partition ?? null,
    resourceType: options.resourceType ?? null,
  }
}

function buildRecord(
  active: ActiveObservedRequest,
  input: {
    at: number
    phase: DesktopObservedRequest['phase']
    status?: number | null
    durationMs?: number | null
    error?: string | null
  },
): DesktopObservedRequest {
  return {
    id: active.id,
    at: input.at,
    phase: input.phase,
    kind: active.kind,
    source: active.source,
    label: active.label,
    method: active.method,
    url: active.url,
    partition: active.partition,
    resourceType: active.resourceType,
    status: input.status ?? null,
    durationMs: input.durationMs ?? null,
    error: input.error ?? null,
  }
}

function pushRecord(record: DesktopObservedRequest): void {
  observedRecords.push(record)
  if (observedRecords.length > maxObservedRecords) {
    observedRecords.splice(0, observedRecords.length - maxObservedRecords)
  }

  if (!rendererTarget || rendererTarget.isDestroyed()) {
    return
  }

  try {
    rendererTarget.send('desktop:network-observed', record)
  } catch {
    // Best-effort diagnostics only.
  }
}