import { NextRequest } from 'next/server'
import { getCurrentUser } from '@/lib/session'
import { prisma } from '@/lib/prisma'
import { FlowStatus } from '@prisma/client'

export const dynamic = 'force-dynamic'

const AGENT_URL = process.env.OPS_AGENT_URL ?? 'http://127.0.0.1:3099'
const AGENT_SECRET = process.env.OPS_AGENT_SECRET ?? ''

export async function POST(request: NextRequest) {
  const user = await getCurrentUser()
  if (!user) {
    return Response.json({ error: 'unauthorized' }, { status: 401 })
  }

  let body: { command_key?: string; args?: string[]; stdin?: string }
  try {
    body = await request.json()
  } catch {
    return Response.json({ error: 'invalid JSON body' }, { status: 400 })
  }

  const { command_key, args = [], stdin } = body
  if (!command_key) {
    return Response.json({ error: 'command_key required' }, { status: 400 })
  }

  const flowRun = await prisma.flowRun.create({
    data: {
      user_id: user.id,
      flow_key: command_key,
      status: FlowStatus.running,
    },
  })

  const flowStep = await prisma.flowStep.create({
    data: {
      flow_run_id: flowRun.id,
      step_index: 0,
      command_key,
      args_json: JSON.stringify(args),
    },
  })

  const encoder = new TextEncoder()

  const stream = new ReadableStream({
    async start(controller) {
      const enqueue = (event: string, data: unknown) => {
        controller.enqueue(
          encoder.encode(`event: ${event}\ndata: ${JSON.stringify(data)}\n\n`),
        )
      }

      enqueue('flow_run_id', { flow_run_id: flowRun.id })

      let agentResponse: Response
      try {
        agentResponse = await fetch(`${AGENT_URL}/agent/v1/exec`, {
          method: 'POST',
          headers: {
            'Content-Type': 'application/json',
            Authorization: `Bearer ${AGENT_SECRET}`,
          },
          body: JSON.stringify({ command_key, args, ...(stdin != null ? { stdin } : {}) }),
        })
      } catch (err) {
        const message = err instanceof Error ? err.message : 'agent unreachable'
        await prisma.flowRun.update({
          where: { id: flowRun.id },
          data: { status: FlowStatus.failed, ended_at: new Date() },
        })
        enqueue('error', { message })
        controller.close()
        return
      }

      if (!agentResponse.ok) {
        const text = await agentResponse.text()
        await prisma.flowRun.update({
          where: { id: flowRun.id },
          data: { status: FlowStatus.failed, ended_at: new Date() },
        })
        enqueue('error', { message: `agent ${agentResponse.status}: ${text}` })
        controller.close()
        return
      }

      const reader = agentResponse.body!.getReader()
      const decoder = new TextDecoder()
      let buffer = ''
      let currentEvent = ''
      let stdout = ''
      let stderr = ''

      try {
        while (true) {
          const { done, value } = await reader.read()
          if (done) break

          buffer += decoder.decode(value, { stream: true })
          const lines = buffer.split('\n')
          buffer = lines.pop() ?? ''

          for (const line of lines) {
            if (line.startsWith('event:')) {
              currentEvent = line.slice(6).trim()
            } else if (line.startsWith('data:')) {
              try {
                const parsed = JSON.parse(line.slice(5).trim()) as Record<string, unknown>
                if (currentEvent === 'stdout') {
                  const chunk = String(parsed.data ?? '')
                  stdout += chunk
                  enqueue('stdout', { data: chunk })
                } else if (currentEvent === 'stderr') {
                  const chunk = String(parsed.data ?? '')
                  stderr += chunk
                  enqueue('stderr', { data: chunk })
                } else if (currentEvent === 'exit') {
                  const exitCode = typeof parsed.code === 'number' ? parsed.code : null
                  const now = new Date()
                  await prisma.flowStep.update({
                    where: { id: flowStep.id },
                    data: { stdout, stderr, exit_code: exitCode, ended_at: now },
                  })
                  await prisma.flowRun.update({
                    where: { id: flowRun.id },
                    data: {
                      status: exitCode === 0 ? FlowStatus.success : FlowStatus.failed,
                      exit_code: exitCode,
                      ended_at: now,
                    },
                  })
                  enqueue('done', { flow_run_id: flowRun.id, exit_code: exitCode })
                } else if (currentEvent === 'error') {
                  const message = String(parsed.message ?? 'unknown error')
                  await prisma.flowRun.update({
                    where: { id: flowRun.id },
                    data: { status: FlowStatus.failed, ended_at: new Date() },
                  })
                  enqueue('error', { message })
                }
              } catch {
                // ignore malformed SSE data
              }
            }
          }
        }
      } catch {
        // stream ended unexpectedly
      }

      controller.close()
    },
  })

  return new Response(stream, {
    headers: {
      'Content-Type': 'text/event-stream',
      'Cache-Control': 'no-cache',
      Connection: 'keep-alive',
    },
  })
}