feat(ai): PR 4 — agent config + validation [4/7]

source/agent-config.js

@@ -0,0 +1,108 @@
+import { readFile } from 'fs/promises';
+import { z } from 'zod';
+import { createError } from 'error-causes';
+import { ValidationError } from './ai-errors.js';
+import { parseOpenCodeNDJSON } from './agent-parser.js';
+
+/**
+ * Format Zod validation errors into a human-readable message.
+ * @param {any} zodError - Zod validation error
+ * @returns {string} Formatted error message
+ */
+export const formatZodError = (zodError) => {
+  const issues = zodError.issues || zodError.errors;
+  return issues
+    ? issues.map(e => `${e.path.join('.')}: ${e.message}`).join('; ')
+    : zodError.message || 'Validation failed';
+};
+
+/**
+ * Get agent configuration based on agent name.
+ * Supports 'claude', 'opencode', and 'cursor' agents.
+ * All agents use their standard OAuth authentication flows.
+ * @param {string} agentName - Name of the agent ('claude', 'opencode', 'cursor')
+ * @returns {Object} Agent configuration with command and args
+ */
+export const getAgentConfig = (agentName = 'claude') => {
+  const agentConfigs = {
+    claude: {
+      command: 'claude',
+      args: ['-p', '--output-format', 'json', '--no-session-persistence']
+    },
+    opencode: {
+      command: 'opencode',
+      args: ['run', '--format', 'json'],
+      parseOutput: (stdout, logger) => parseOpenCodeNDJSON(stdout, logger)
+    },
+    cursor: {
+      command: 'agent',
+      args: ['--print', '--output-format', 'json', '--trust']
+    }
+  };
+
+  const config = agentConfigs[agentName.toLowerCase()];
+  if (!config) {
+    throw createError({
+      ...ValidationError,
+      message: `Unknown agent: ${agentName}. Supported agents: ${Object.keys(agentConfigs).join(', ')}`
+    });
+  }
+
+  return config;
+};
+
+// YAGNI: only command + args — parseOutput is a runtime function, not a serializable config field
+const agentConfigFileSchema = z.object({
+  command: z.string().min(1, { error: 'command is required' }),
+  args: z.array(z.string()).default([])
+});
+
+const readAgentConfigFile = async ({ configPath }) => {
+  try {
+    return await readFile(configPath, 'utf-8');
+  } catch (err) {
+    throw createError({
+      ...ValidationError,
+      message: `Failed to read agent config file: ${configPath}`,
+      code: 'AGENT_CONFIG_READ_ERROR',
+      cause: err
+    });
+  }
+};
+
+const parseJson = ({ configPath, raw }) => {
+  try {
+    return JSON.parse(raw);
+  } catch (err) {
+    throw createError({
+      ...ValidationError,
+      message: `Agent config file is not valid JSON: ${configPath}`,
+      code: 'AGENT_CONFIG_PARSE_ERROR',
+      cause: err
+    });
+  }
+};
+
+const validateAgentConfig = (parsed) => {
+  try {
+    return agentConfigFileSchema.parse(parsed);
+  } catch (zodError) {
+    throw createError({
+      ...ValidationError,
+      message: `Invalid agent config: ${formatZodError(zodError)}`,
+      code: 'AGENT_CONFIG_VALIDATION_ERROR',
+      cause: zodError
+    });
+  }
+};
+
+/**
+ * Load and validate an agent configuration from a JSON file.
+ * @param {string} configPath - Path to the JSON config file
+ * @returns {Promise<Object>} Validated agent config with command and args
+ */
+export const loadAgentConfig = async (configPath) => {
+  const raw = await readAgentConfigFile({ configPath });
+  const parsed = parseJson({ configPath, raw });
+  return validateAgentConfig(parsed);
+};