src/bot.ts

// Node 20 includes native fetch support

// AI Client for Groq with Failover Support + Circuit Breaker
// Fallback shims for Probot runtime
/* eslint-disable no-console */
import {
  ChatGPTAPI as AIClient,
  ChatGPTError as AIError,
  ChatMessage,
  SendMessageOptions
} from 'chatgpt'
import pRetry from 'p-retry'
import CircuitBreaker from 'opossum'
import {AIOptions, Options} from './options'
import {TokenLimits} from './limits'
import pino from 'pino'

const logger = pino({ level: process.env.LOG_LEVEL || 'info' })

// Circuit breaker configuration
const CIRCUIT_BREAKER_OPTIONS = {
  timeout: 60000, // 60 seconds
  errorThresholdPercentage: 50,
  resetTimeout: 30000,
  volumeThreshold: 5,
}

const logInfo = (msg: string) => logger.info(msg)
const logWarning = (msg: string) => logger.warn(msg)
const logError = (msg: string) => logger.error(msg)
const setFailed = (msg: string) => {
  logger.error(msg)
  process.exit(1)
}

export interface Ids {
  parentMessageId?: string
  conversationId?: string
}

export class Bot {
  private api: AIClient | null = null
  private readonly options: Options
  private readonly aiOptions: AIOptions
  private currentModel: string
  private fallbackModels: string[]
  private circuitBreaker: CircuitBreaker | null = null

  constructor(options: Options, aiOptions: AIOptions) {
    this.options = options
    this.aiOptions = aiOptions
    this.currentModel = aiOptions.model

    // Setup fallback chain based on tier
    if (Options.HEAVY_MODELS.includes(this.currentModel)) {
      this.fallbackModels = [...Options.HEAVY_MODELS]
    } else {
      this.fallbackModels = [...Options.LIGHT_MODELS]
    }

    // Remove current model from fallbacks to avoid immediate repeat
    this.fallbackModels = this.fallbackModels.filter(
      m => m !== this.currentModel
    )

    this.initClient()
    this.initCircuitBreaker()
  }

  private initCircuitBreaker(): void {
    if (!this.api) return

    // Wrap the sendMessage method with circuit breaker
    this.circuitBreaker = new CircuitBreaker(
      async ({ message, opts }: { message: string; opts: SendMessageOptions }) => {
        return this.api!.sendMessage(message, opts)
      },
      CIRCUIT_BREAKER_OPTIONS
    )

    // Circuit breaker event handlers
    this.circuitBreaker.on('open', () => {
      logWarning(`Circuit breaker opened for model: ${this.currentModel}`)
    })

    this.circuitBreaker.on('halfOpen', () => {
      logInfo(`Circuit breaker half-open for model: ${this.currentModel}`)
    })

    this.circuitBreaker.on('close', () => {
      logInfo(`Circuit breaker closed for model: ${this.currentModel}`)
    })

    this.circuitBreaker.on('fallback', (_result: unknown) => {
      logWarning(`Circuit breaker fallback executed for model: ${this.currentModel}`)
    })
  }

  private initClient(): void {
    const apiKey = process.env.GROQ_API_KEY || process.env.AI_API_KEY
    if (apiKey) {
      const currentDate = new Date().toISOString().split('T')[0]
      const limits = new TokenLimits(this.currentModel)
      const systemMessage = `${this.options.systemMessage} 
Knowledge cutoff: ${limits.knowledgeCutOff}
Current date: ${currentDate}
IMPORTANT: Entire response must be in ISO code: ${this.options.language}
`

      this.api = new AIClient({
        apiBaseUrl: this.options.apiBaseUrl,
        systemMessage,
        apiKey,
        apiOrg: process.env.AI_API_ORG || undefined,
        debug: this.options.debug,
        maxModelTokens: limits.maxTokens,
        maxResponseTokens: limits.responseTokens,
        completionParams: {
          temperature: this.options.modelTemperature,
          model: this.currentModel
        }
      })
      logInfo(`Initialized AI client with model: ${this.currentModel}`)
    } else {
      throw new Error("Missing 'GROQ_API_KEY' or 'AI_API_KEY'")
    }
  }

  chat = async (message: string, ids: Ids): Promise<[string, Ids]> => {
    let res: [string, Ids] = ['', {}]
    try {
      res = await this.chat_(message, ids)
      return res
    } catch (e: unknown) {
      if (e instanceof AIError) {
        logWarning(`AI communication error: ${e.message}`)
      }
      return res
    }
  }

  private readonly chat_ = async (
    message: string,
    ids: Ids
  ): Promise<[string, Ids]> => {
    const start = Date.now()
    if (!message) return ['', {}]

    let response: ChatMessage | undefined

    if (this.api != null) {
      const opts: SendMessageOptions = {
        timeoutMs: this.options.timeoutMS
      }
      if (ids.parentMessageId) {
        opts.parentMessageId = ids.parentMessageId
      }

      try {
        // Check if circuit breaker is open
        if (this.circuitBreaker?.opened) {
          logWarning(`Circuit breaker is OPEN for ${this.currentModel}, attempting fallback...`)
          if (this.fallbackModels.length > 0) {
            const nextModel = this.fallbackModels.shift()
            if (nextModel) {
              this.currentModel = nextModel
              this.initClient()
              this.initCircuitBreaker()
              // Recursive retry with new model
              return this.chat_(message, ids)
            }
          }
          throw new Error(`Circuit breaker open and no fallback models available for ${this.currentModel}`)
        }

        const result = await pRetry<ChatMessage>(
          async () => {
            if (!this.circuitBreaker) {
              throw new Error('Circuit breaker not initialized')
            }
            try {
              const messageResult = await this.circuitBreaker.fire({ message, opts })
              return messageResult as ChatMessage
            } catch (e: any) {
              // Check if circuit breaker opened
              if (this.circuitBreaker.opened && this.fallbackModels.length > 0) {
                const nextModel = this.fallbackModels.shift()
                if (nextModel) {
                  logWarning(
                    `Circuit breaker opened for ${this.currentModel}. Switching to fallback: ${nextModel}`
                  )
                  this.currentModel = nextModel
                  this.initClient()
                  this.initCircuitBreaker()
                  // Throw to trigger retry with new model
                  throw new Error(`Model switched to ${nextModel}, retrying...`)
                }
              }
              
              // Handle rate limiting / context size
              if ((e?.status === 429 || e?.status === 413) && this.fallbackModels.length > 0) {
                const nextModel = this.fallbackModels.shift()
                if (nextModel) {
                  logWarning(
                    `Rate limit or context size error (${e.status}) hit for ${this.currentModel}. Switching to fallback: ${nextModel}`
                  )
                  this.currentModel = nextModel
                  this.initClient()
                  this.initCircuitBreaker()
                  throw new Error(`Model switched to ${nextModel}, retrying...`)
                }
              }
              throw e
            }
          },
          {
            retries: this.options.retries,
            minTimeout: 20000, // 20s delay to allow TPM refresh
            onFailedAttempt: (err: any) => {
              logInfo(
                `Attempt ${err.attemptNumber} failed. ${err.retriesLeft} retries left. Error: ${err.message}`
              )
            }
          }
        )
        response = result
      } catch (e: unknown) {
        if (e instanceof AIError) {
          logWarning(
            `AI Error after retries: ${e.message} (Last model used: ${this.currentModel})`
          )
        } else if (e instanceof Error) {
          logError(`Failed to get AI response: ${e.message}`)
        }
      }

      const end = Date.now()
      logInfo(`AI response time: ${end - start} ms`)
    } else {
      setFailed('AI client is not initialized')
    }

    let responseText = ''
    if (response != null) {
      responseText = response.text
    }

    const newIds: Ids = {
      parentMessageId: response?.id,
      conversationId: response?.conversationId
    }
    return [responseText, newIds]
  }
}