import { describe, expect, it } from 'vitest'
import {
  CHAT_TRUNCATION_MARKER,
  fitChatRequest,
  LLM_PROXY_CHAT_LIMITS,
  toChatRequest,
  toRoleMessages,
} from '../src/llm-chat'

describe('toChatRequest', () => {
  it('separates system messages from turns and keeps turn order', () => {
    expect(toChatRequest([
      { role: 'system', content: 'persona' },
      { role: 'user', content: 'hi' },
      { role: 'assistant', content: 'hello' },
      { role: 'user', content: 'again' },
    ])).toEqual({
      system: 'persona',
      turns: [
        { role: 'user', content: 'hi' },
        { role: 'assistant', content: 'hello' },
        { role: 'user', content: 'again' },
      ],
    })
  })

  it('joins several system messages and drops non-chat roles', () => {
    expect(toChatRequest([
      { role: 'system', content: 'a' },
      { role: 'tool', content: 'ignored' },
      { role: 'system', content: 'b' },
      { role: 'system', content: '   ' },
      { role: 'user', content: 'q' },
    ])).toEqual({ system: 'a\n\nb', turns: [{ role: 'user', content: 'q' }] })
  })

  it('omits system when there is none', () => {
    expect(toChatRequest([{ role: 'user', content: 'q' }])).toEqual({
      turns: [{ role: 'user', content: 'q' }],
    })
  })
})

describe('toRoleMessages', () => {
  it('round-trips a canonical Ollama message list unchanged', () => {
    const messages = [
      { role: 'system', content: 'persona' },
      { role: 'user', content: 'hi' },
      { role: 'assistant', content: 'hello' },
    ]
    expect(toRoleMessages(toChatRequest(messages))).toEqual(messages)
  })

  it('puts the system message first', () => {
    expect(toRoleMessages({ system: 's', turns: [{ role: 'user', content: 'u' }] })).toEqual([
      { role: 'system', content: 's' },
      { role: 'user', content: 'u' },
    ])
  })
})

describe('fitChatRequest', () => {
  const limits = { maxSystemChars: 50, maxMessageChars: 20, maxMessages: 3, maxTotalChars: 40 }

  it('keeps the head of an over-long system prompt within the limit', () => {
    const system = `INSTRUCTIONS ${'x'.repeat(200)}`
    const fitted = fitChatRequest({ system, turns: [{ role: 'user', content: 'q' }] }, limits)
    expect(fitted.system?.length).toBeLessThanOrEqual(limits.maxSystemChars)
    expect(fitted.system?.startsWith('INSTRUCTIONS')).toBe(true)
    expect(fitted.system?.endsWith(CHAT_TRUNCATION_MARKER)).toBe(true)
  })

  it('drops empty turns such as an empty assistant reply', () => {
    const fitted = fitChatRequest({
      turns: [
        { role: 'user', content: 'q1' },
        { role: 'assistant', content: '' },
        { role: 'user', content: 'q2' },
      ],
    }, limits)
    expect(fitted.turns).toEqual([
      { role: 'user', content: 'q1' },
      { role: 'user', content: 'q2' },
    ])
  })

  it('keeps the newest turns within count and size limits and never starts with assistant', () => {
    const fitted = fitChatRequest({
      turns: [
        { role: 'user', content: 'u1' },
        { role: 'assistant', content: 'a1' },
        { role: 'user', content: 'u2' },
        { role: 'assistant', content: 'a2' },
        { role: 'user', content: 'u3' },
      ],
    }, limits)
    // maxMessages=3 keeps [u2, a2, u3]
    expect(fitted.turns.map((t) => t.content)).toEqual(['u2', 'a2', 'u3'])

    const trimmed = fitChatRequest({
      turns: [
        { role: 'user', content: 'u'.repeat(20) },
        { role: 'assistant', content: 'a'.repeat(15) },
        { role: 'user', content: 'q'.repeat(20) },
      ],
    }, limits)
    // total 40: [a(15), q(20)] fits, then the leading assistant turn is dropped
    expect(trimmed.turns).toEqual([{ role: 'user', content: 'q'.repeat(20) }])
  })

  it('truncates a single turn over the per-message limit', () => {
    const fitted = fitChatRequest({ turns: [{ role: 'user', content: 'z'.repeat(100) }] }, limits)
    expect(fitted.turns[0].content.length).toBeLessThanOrEqual(limits.maxMessageChars)
  })

  it('exposes the llm-proxy limits', () => {
    expect(LLM_PROXY_CHAT_LIMITS).toEqual({
      maxSystemChars: 8_000,
      maxMessageChars: 8_000,
      maxMessages: 40,
      maxTotalChars: 50_000,
    })
  })
})