/**
 * The default preset is a user setting. `config.default` is the deployment's
 * engineering default; the settings document overrides it and is hot-reloaded,
 * so a person can change which preset new sessions get without a restart.
 */

import { mkdtemp, writeFile } from 'node:fs/promises'
import { tmpdir } from 'node:os'
import { dirname, join } from 'node:path'
import { fileURLToPath, pathToFileURL } from 'node:url'
import { Context } from 'cordis'
import Loader from '@cordisjs/plugin-loader'
import Include from '@cordisjs/plugin-include'
import LlmService from '@deepseek-ai/dsh-llm'
import SessionStore, { SessionId } from '@deepseek-ai/dsh-session'
import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
import ToolRegistry from '@deepseek-ai/dsh-tools'
import AgentRegistry from '@deepseek-ai/dsh-agent'
import AgentLoop from '@deepseek-ai/dsh-agent-loop'
import SettingsLocal from '@deepseek-ai/dsh-settings-local'
import { settingsNamespace } from '@deepseek-ai/dsh-settings'
import { describe, expect, it } from 'vitest'
import AgentPresets, { SETTINGS_NAMESPACE } from '@deepseek-ai/dsh-agent-presets'

const FIXTURES = join(dirname(fileURLToPath(import.meta.url)), 'fixtures')
const ROOTS = [{ path: join(FIXTURES, 'system'), trust: 'system' as const }]
const NS = settingsNamespace(SETTINGS_NAMESPACE)

/**
 * A composition with a real file-backed settings provider. `settingsFiber` is
 * the provider's own handle, so a test can take it away the way a reload does.
 */
async function harness(): Promise<{ ctx: Context; settingsFile: string; settingsFiber: { dispose: () => unknown } }> {
  const home = await mkdtemp(join(tmpdir(), 'dsh-preset-settings-'))
  const settingsFile = join(home, 'settings.yaml')
  await writeFile(settingsFile, '{}\n')

  const ctx = new Context()
  ctx.baseUrl = pathToFileURL(FIXTURES).href + '/'
  await ctx.plugin(Loader)
  ctx.loader.builtins.include = Include
  await ctx.plugin(LlmService)
  await ctx.plugin(SessionStore)
  await ctx.plugin(SystemPrompt, { persona: '' })
  await ctx.plugin(ToolRegistry)
  await ctx.plugin(AgentRegistry)
  await ctx.plugin(AgentLoop, { agents: [] })
  const settingsFiber = ctx.plugin(SettingsLocal, { path: settingsFile, watch: false })
  await settingsFiber
  await ctx.plugin(AgentPresets, { default: 'standard', roots: ROOTS })
  return { ctx, settingsFile, settingsFiber }
}

const toolNames = (ctx: Context, agent?: unknown): string[] =>
  ctx.tools.schemas(agent as never).map(schema => schema.name).sort()

describe('the default preset as a user setting', () => {
  it('falls back to the composition default while the user set none', async () => {
    const { ctx } = await harness()

    expect(ctx.agentPresets.defaultId).toBe('standard')
  })

  it('takes the user default over the composition default', async () => {
    const { ctx } = await harness()

    await ctx.settings.update(NS, { default: 'minimal' })

    expect(ctx.agentPresets.defaultId).toBe('minimal')
  })

  it('composes a new session from the user default', async () => {
    const { ctx } = await harness()
    await ctx.settings.update(NS, { default: 'minimal' })

    const handle = await ctx.agents.create({
      sessionId: SessionId('settings-default'),
      setup: async (agentCtx: Context) => void await ctx.agentPresets.mount(agentCtx),
    })
    try {
      expect(toolNames(ctx, handle.agent)).toEqual(['beta'])
    } finally {
      await handle.dispose()
    }
  })

  it('leaves a running session on the preset it was composed from', async () => {
    const { ctx } = await harness()
    const running = await ctx.agents.create({
      sessionId: SessionId('settings-running'),
      setup: async (agentCtx: Context) => void await ctx.agentPresets.mount(agentCtx),
    })
    try {
      expect(toolNames(ctx, running.agent)).toEqual(['alpha'])

      // Changing the default mid-flight must not reach an agent that already
      // composed: its history was produced under `standard`'s tools.
      await ctx.settings.update(NS, { default: 'minimal' })

      expect(ctx.agentPresets.defaultId).toBe('minimal')
      expect(toolNames(ctx, running.agent)).toEqual(['alpha'])
    } finally {
      await running.dispose()
    }
  })

  it('re-inherits the composition default when the user setting is cleared', async () => {
    const { ctx } = await harness()
    await ctx.settings.update(NS, { default: 'minimal' })
    expect(ctx.agentPresets.defaultId).toBe('minimal')

    await ctx.settings.replace(NS, {})

    expect(ctx.agentPresets.defaultId).toBe('standard')
  })

  it('reports an unknown user default only when a session tries to use it', async () => {
    const { ctx } = await harness()

    // Storing it succeeds — the roster is a live directory, so a name that is
    // absent now may exist by the time a session asks for it.
    await ctx.settings.update(NS, { default: 'no-such-preset' })

    await expect(ctx.agentPresets.resolve())
      .rejects.toThrow(/preset "no-such-preset" not found/)
  })
})

describe('a settings provider that goes away', () => {
  it('falls back to the composition default when the provider unloads', async () => {
    const { ctx, settingsFiber } = await harness()
    await ctx.settings.update(NS, { default: 'minimal' })
    expect(ctx.agentPresets.defaultId).toBe('minimal')

    // Unloading the provider takes the user layer with it; the roster keeps
    // working on its composition default rather than holding a stale override.
    await settingsFiber.dispose()

    expect(ctx.agentPresets.defaultId).toBe('standard')
  })
})