openpencil/server/api/ai/validate.ts

import { defineEventHandler, readBody, setResponseHeaders } from 'h3'
import { resolveClaudeCli } from '../../utils/resolve-claude-cli'
import {
  buildClaudeAgentEnv,
  getClaudeAgentDebugFilePath,
} from '../../utils/resolve-claude-agent-env'
import { writeFile, mkdtemp, rm } from 'node:fs/promises'
import { tmpdir } from 'node:os'
import { join } from 'node:path'
import { runCodexExec } from '../../utils/codex-client'

interface ValidateBody {
  system: string
  message: string
  imageBase64: string
  model?: string
  provider?: 'anthropic' | 'openai' | 'opencode'
}

/**
 * Vision-based validation endpoint.
 * Accepts a base64 PNG screenshot and a text prompt, sends multimodal
 * content blocks for analysis via Agent SDK.
 *
 * Saves screenshot to temp file, asks Claude Code to read it via its
 * built-in Read tool.
 */
export default defineEventHandler(async (event) => {
  const body = await readBody<ValidateBody>(event)

  if (!body?.system || !body?.message || !body?.imageBase64) {
    setResponseHeaders(event, { 'Content-Type': 'application/json' })
    return { error: 'Missing required fields: system, message, imageBase64' }
  }

  if (!body.model?.trim()) {
    setResponseHeaders(event, { 'Content-Type': 'application/json' })
    return { error: 'Missing model. Model fallback is disabled.' }
  }

  try {
    if (body.provider === 'anthropic') {
      return await validateViaAgentSDK(body, body.model)
    }
    if (body.provider === 'openai') {
      return await validateViaCodex(body, body.model)
    }
    if (body.provider === 'opencode') {
      return await validateViaOpenCode(body, body.model)
    }
    return { error: 'Missing or unsupported provider. Provider fallback is disabled.' }
  } catch (error) {
    const message = error instanceof Error ? error.message : 'Unknown error'
    return { error: message }
  }
})

function toImageBase64(data: string): string {
  const dataUrlPrefix = 'data:image/png;base64,'
  return data.startsWith(dataUrlPrefix) ? data.slice(dataUrlPrefix.length) : data
}

async function withTempImageFile<T>(
  imageBase64: string,
  run: (tempPath: string) => Promise<T>,
): Promise<T> {
  const tempDir = await mkdtemp(join(tmpdir(), 'openpencil-validate-'))
  const tempPath = join(tempDir, 'screenshot.png')
  try {
    await writeFile(tempPath, Buffer.from(toImageBase64(imageBase64), 'base64'))
    return await run(tempPath)
  } finally {
    await rm(tempDir, { recursive: true, force: true }).catch(() => {})
  }
}

/**
 * Agent SDK fallback: save screenshot to a temp PNG file, then ask Claude
 * Code to read it (Claude Code's Read tool supports images natively).
 */
async function validateViaAgentSDK(
  body: ValidateBody,
  model?: string,
): Promise<{ text: string; skipped?: boolean; error?: string }> {
  return await withTempImageFile(body.imageBase64, async (tempPath) => {
    const { query } = await import('@anthropic-ai/claude-agent-sdk')

    const env = buildClaudeAgentEnv()
    const debugFile = getClaudeAgentDebugFilePath()

    const claudePath = resolveClaudeCli()

    // Prompt Claude Code to read the temp image and analyze it
    const prompt = `Read the image file at "${tempPath}" and analyze it as a UI design screenshot.

${body.message}

${body.system}

Output ONLY the JSON object, no markdown fences, no explanation.`

    const q = query({
      prompt,
      options: {
        ...(model ? { model } : {}),
        maxTurns: 2,
        tools: [],
        plugins: [],
        permissionMode: 'plan',
        persistSession: false,
        env,
        ...(debugFile ? { debugFile } : {}),
        ...(claudePath ? { pathToClaudeCodeExecutable: claudePath } : {}),
      },
    })

    try {
      for await (const message of q) {
        if (message.type === 'result') {
          const isErrorResult = 'is_error' in message && Boolean((message as { is_error?: boolean }).is_error)
          if (message.subtype === 'success' && !isErrorResult) {
            return { text: message.result }
          }
          const errors = 'errors' in message ? (message.errors as string[]) : []
          const resultText = 'result' in message ? String(message.result ?? '') : ''
          return { error: errors.join('; ') || resultText || `Query ended with: ${message.subtype}`, text: '' }
        }
      }
    } finally {
      q.close()
    }

    return { text: '', skipped: true }
  })
}

async function validateViaCodex(
  body: ValidateBody,
  model?: string,
): Promise<{ text: string; skipped?: boolean; error?: string }> {
  return await withTempImageFile(body.imageBase64, async (tempPath) => {
    const result = await runCodexExec(
      `${body.message}\n\nOutput ONLY the JSON object, no markdown fences, no explanation.`,
      {
        model,
        systemPrompt: body.system,
        imageFiles: [tempPath],
      },
    )
    if (result.error) {
      return { text: '', error: result.error }
    }
    return { text: result.text ?? '' }
  })
}

function parseOpenCodeModel(model?: string): { providerID: string; modelID: string } | undefined {
  if (!model || !model.includes('/')) return undefined
  const idx = model.indexOf('/')
  return { providerID: model.slice(0, idx), modelID: model.slice(idx + 1) }
}

async function validateViaOpenCode(
  body: ValidateBody,
  model?: string,
): Promise<{ text: string; skipped?: boolean; error?: string }> {
  let ocServer: { close(): void } | undefined
  try {
    const { getOpencodeClient } = await import('../../utils/opencode-client')
    const oc = await getOpencodeClient()
    const ocClient: any = oc.client
    ocServer = oc.server

    const { data: session, error: sessionError } = await ocClient.session.create({
      title: 'OpenPencil Validate',
    })
    if (sessionError || !session) {
      return { text: '', error: 'Failed to create OpenCode session' }
    }

    await ocClient.session.prompt({
      sessionID: session.id,
      noReply: true,
      parts: [{ type: 'text', text: body.system }],
    })

    const parsed = parseOpenCodeModel(model)
    if (!parsed) {
      return { text: '', error: 'Invalid OpenCode model format. Expected "provider/model".' }
    }

    const base64 = toImageBase64(body.imageBase64)
    const promptPayload = {
      sessionID: session.id,
      model: parsed,
      parts: [
        { type: 'image', url: `data:image/png;base64,${base64}` },
        {
          type: 'text',
          text: `${body.message}\n\nOutput ONLY the JSON object, no markdown fences, no explanation.`,
        },
      ],
    }

    const { data: result, error: promptError } = await ocClient.session.prompt(promptPayload)
    if (promptError) {
      return { text: '', error: 'OpenCode validation failed' }
    }

    const texts: string[] = []
    if (result?.parts) {
      for (const part of result.parts) {
        if (part.type === 'text' && part.text) {
          texts.push(part.text)
        }
      }
    }
    return { text: texts.join('') }
  } catch (error) {
    const message = error instanceof Error ? error.message : 'Unknown error'
    return { text: '', error: message }
  } finally {
    const { releaseOpencodeServer } = await import('../../utils/opencode-client')
    releaseOpencodeServer(ocServer)
  }
}