import { createServer } from 'node:http'
import type { IncomingMessage, Server, ServerResponse } from 'node:http'
import { afterEach, describe, expect, it } from 'vitest'
import { Context } from 'cordis'
import LlmService, { userAgent } from '@deepseek-ai/dsh-llm'
import * as LlmPiAi from '@deepseek-ai/dsh-llm-pi-ai'
import { getBuiltinModels } from '@earendil-works/pi-ai/providers/all'
import { discoverModels } from '../src/discovery.ts'

const servers: Server[] = []

afterEach(async () => {
  await Promise.all(servers.splice(0).map(server => new Promise(resolve => server.close(resolve))))
})

interface ListingServer {
  url: string
  paths: string[]
  headers: IncomingMessage['headers'][]
}

/**
 * A stand-in provider that answers one scripted `GET /models`. `chunks` writes
 * without a declared length, which is how a real streamed reply arrives.
 */
async function listingServer(behavior: {
  status?: number
  body?: string
  chunks?: string[]
  holdOpenMs?: number
}): Promise<ListingServer> {
  const paths: string[] = []
  const headers: IncomingMessage['headers'][] = []
  const server = createServer((request: IncomingMessage, response: ServerResponse) => {
    paths.push(request.url ?? '')
    headers.push(request.headers)
    if (behavior.chunks !== undefined) {
      // No declared length: the ceiling has to hold on what is read.
      response.writeHead(behavior.status ?? 200, { 'content-type': 'application/json' })
      for (const chunk of behavior.chunks) response.write(chunk)
      if (behavior.holdOpenMs === undefined) { response.end(); return }
      // Left open so a caller's cancellation lands while the body is still
      // being read rather than after it completed.
      setTimeout(() => { response.end() }, behavior.holdOpenMs)
      return
    }
    const body = behavior.body ?? '{}'
    response.writeHead(behavior.status ?? 200, {
      'content-type': 'application/json',
      'content-length': String(Buffer.byteLength(body)),
    })
    response.end(body)
  })
  servers.push(server)
  await new Promise<void>(resolve => server.listen(0, '127.0.0.1', resolve))
  const address = server.address()
  if (address === null || typeof address === 'string') throw new Error('no port')
  return { url: `http://127.0.0.1:${address.port}`, paths, headers }
}

/** A bare dormant mount: discovery is offered whether or not a route exists. */
async function harness(): Promise<Context> {
  const ctx = new Context()
  await ctx.plugin(LlmService)
  await ctx.plugin(LlmPiAi, {})
  return ctx
}

describe('catalog-route model discovery', () => {
  it('answers from the installed registry, with capacities and no network call', async () => {
    const server = await listingServer({ body: JSON.stringify({ data: [{ id: 'from-the-endpoint' }] }) })
    const ctx = await harness()

    const models = await ctx.llm.discoverModels('llm-pi-ai', { provider: 'deepseek', baseURL: server.url })

    // pi-ai's own registry is the authority for its own providers, and it
    // carries what a listing endpoint would not disclose.
    expect(models.map(model => model.id).sort())
      .toEqual(getBuiltinModels('deepseek').map(model => model.id).sort())
    expect(models.every(model => (model.contextWindow ?? 0) > 0 && (model.maxTokens ?? 0) > 0)).toBe(true)
    expect(server.paths).toEqual([])
  })

  it('needs no endpoint for a route the catalog describes', async () => {
    const ctx = await harness()
    await expect(ctx.llm.discoverModels('llm-pi-ai', { provider: 'deepseek' })).resolves.not.toHaveLength(0)
  })

  it('says where a route the catalog does not describe must get its models', async () => {
    const ctx = await harness()
    await expect(ctx.llm.discoverModels('llm-pi-ai', { provider: 'acme-gateway' }))
      .rejects.toThrow(/ships no catalog for provider "acme-gateway".*set a baseURL/s)
    // A form that cleared the field says the same thing as one that never had it.
    await expect(ctx.llm.discoverModels('llm-pi-ai', { provider: 'acme-gateway', baseURL: '' }))
      .rejects.toThrow(/set a baseURL/)
    // The seam refuses a request naming neither, so the module's own guard for
    // that shape is only reachable by calling it directly.
    await expect(discoverModels({})).rejects.toThrow(/set a baseURL/)
  })
})

describe('draft-provider model discovery', () => {
  it('reads an OpenAI-compatible listing and keeps the capacities it discloses', async () => {
    const server = await listingServer({
      body: JSON.stringify({
        data: [
          { id: 'acme-large', display_name: 'Acme Large', context_length: 65_536, max_output_tokens: 4096 },
          { id: 'acme-small' },
        ],
      }),
    })
    const ctx = await harness()

    const models = await ctx.llm.discoverModels('llm-pi-ai', { baseURL: `${server.url}/v1`, apiKey: 'probe-key' })

    expect(models).toEqual([
      { id: 'acme-large', name: 'Acme Large', contextWindow: 65_536, maxTokens: 4096 },
      { id: 'acme-small' },
    ])
    expect(server.paths).toEqual(['/v1/models'])
    expect(server.headers[0]?.authorization).toBe('Bearer probe-key')
    expect(server.headers[0]?.['user-agent']).toBe(userAgent())
  })

  it('keeps a deployment path instead of resolving it away', async () => {
    const server = await listingServer({ body: JSON.stringify({ data: [{ id: 'm' }] }) })
    const ctx = await harness()

    await ctx.llm.discoverModels('llm-pi-ai', { baseURL: `${server.url}/openai/v1/` })

    expect(server.paths).toEqual(['/openai/v1/models'])
  })

  it('offers no credential when the draft names none', async () => {
    const server = await listingServer({ body: JSON.stringify({ data: [{ id: 'm' }] }) })
    const ctx = await harness()

    await ctx.llm.discoverModels('llm-pi-ai', { baseURL: server.url })

    expect(server.headers[0]?.authorization).toBeUndefined()
  })

  it('drops unusable rows rather than failing the whole listing', async () => {
    const server = await listingServer({
      body: JSON.stringify({
        data: [
          { id: 'good' },
          { id: '' },
          { name: 'no id at all' },
          null,
          { id: 'good' },
          { id: 'zero-capacity', context_length: 0, max_tokens: -1 },
        ],
      }),
    })
    const ctx = await harness()

    expect(await ctx.llm.discoverModels('llm-pi-ai', { baseURL: server.url }))
      .toEqual([{ id: 'good' }, { id: 'zero-capacity' }])
  })

  it('points at the credential for a rejected one, and only then', async () => {
    const ctx = await harness()

    for (const status of [401, 403]) {
      const refused = await listingServer({ status, body: '{"error":"nope"}' })
      await expect(ctx.llm.discoverModels('llm-pi-ai', { baseURL: refused.url, apiKey: 'wrong' }))
        .rejects.toThrow(new RegExp(`answered ${status}; check the API key`))
    }

    // A server fault is not a credential problem, so it must not send the user
    // off to re-check a key that is fine.
    const broken = await listingServer({ status: 500, body: '{"error":"boom"}' })
    await expect(ctx.llm.discoverModels('llm-pi-ai', { baseURL: broken.url, apiKey: 'fine' }))
      .rejects.toThrow(/answered 500$/)
  })

  it('reports a reply that is not a model listing', async () => {
    const server = await listingServer({ body: '{"models":[]}' })
    const ctx = await harness()

    await expect(ctx.llm.discoverModels('llm-pi-ai', { baseURL: server.url }))
      .rejects.toThrow(/no "data" array; enter this provider's models by hand/)

    const broken = await listingServer({ body: 'not json at all' })
    await expect(ctx.llm.discoverModels('llm-pi-ai', { baseURL: broken.url }))
      .rejects.toThrow(/did not answer with JSON/)
  })

  it('refuses an oversized reply, whether its length is declared or streamed', async () => {
    const ctx = await harness()
    // Just over the four-megabyte ceiling, as one padded model row.
    const oversized = `{"data":[{"id":"m","pad":"${'x'.repeat(4 * 1024 * 1024)}"}]}`

    const declared = await listingServer({ body: oversized })
    await expect(ctx.llm.discoverModels('llm-pi-ai', { baseURL: declared.url }))
      .rejects.toThrow(/answered with more than 4194304 bytes/)

    // A streamed reply declares no length, so the ceiling has to hold on the
    // body the harness actually read.
    const streamed = await listingServer({ chunks: ['{"data":[{"id":"m","pad":"', 'x'.repeat(4 * 1024 * 1024), '"}]}'] })
    await expect(ctx.llm.discoverModels('llm-pi-ai', { baseURL: streamed.url }))
      .rejects.toThrow(/answered with more than 4194304 bytes/)
  })

  it('reports an unreachable endpoint instead of an empty catalog', async () => {
    const ctx = await harness()
    // Port 9 is the discard service: nothing accepts a connection there.
    await expect(ctx.llm.discoverModels('llm-pi-ai', { baseURL: 'http://127.0.0.1:9/v1' }))
      .rejects.toMatchObject({ code: 'DISCOVERY_FAILED' })
  })

  it.each(['anthropic-messages', 'azure-openai-responses', 'openai-codex-responses', 'google-generative-ai'])(
    'says it cannot interrogate %s rather than guessing a shape',
    async (api) => {
      // Azure authenticates with an `api-key` header and an `api-version`
      // query despite its OpenAI lineage, and Codex uses OAuth; guessing at
      // either would report an auth failure as a provider with no models.
      const ctx = await harness()
      await expect(ctx.llm.discoverModels('llm-pi-ai', { baseURL: 'https://gateway.example/v1', api }))
        .rejects.toMatchObject({ code: 'DISCOVERY_UNSUPPORTED' })
    },
  )

  it('reports cancellation during the body read as an abort, not a raw reason', async () => {
    const ctx = await harness()
    const controller = new AbortController()
    // Chunked, so the headers arrive and the cancellation lands mid-body.
    const slow = await listingServer({ chunks: ['{"data":[', '{"id":"a"}'], holdOpenMs: 400 })
    const probe = ctx.llm.discoverModels('llm-pi-ai', { baseURL: slow.url, signal: controller.signal })
    setTimeout(() => { controller.abort('test cancellation') }, 40)

    await expect(probe).rejects.toMatchObject({ code: 'ABORTED' })
  })

  it('honors caller cancellation', async () => {
    const ctx = await harness()
    const aborted = AbortSignal.abort('test cancellation')
    await expect(ctx.llm.discoverModels('llm-pi-ai', {
      baseURL: 'http://127.0.0.1:9/v1',
      signal: aborted,
    })).rejects.toMatchObject({ code: 'ABORTED' })
  })

  it('is offered for the namespace, and refuses one it does not serve', async () => {
    const ctx = await harness()

    expect(ctx.llm.listModelDiscoveryNamespaces()).toEqual(['llm-pi-ai'])
    await expect(ctx.llm.discoverModels('llm-deepseek', { baseURL: 'https://api.deepseek.com' }))
      .rejects.toMatchObject({ code: 'NO_DISCOVERY' })
    await expect(ctx.llm.discoverModels('llm-pi-ai', { baseURL: '' }))
      .rejects.toMatchObject({ code: 'INVALID_DISCOVERY' })
  })

  it('withdraws the offer when the plugin unloads', async () => {
    const ctx = new Context()
    await ctx.plugin(LlmService)
    const fiber = await ctx.plugin(LlmPiAi, {})
    expect(ctx.llm.listModelDiscoveryNamespaces()).toEqual(['llm-pi-ai'])

    await fiber.dispose()

    expect(ctx.llm.listModelDiscoveryNamespaces()).toEqual([])
  })
})