refactor: modularize architecture for improved maintainability (#67)

Extract monolithic index.js (395 lines) into modular architecture:

- src/cli/: Command handlers with dependency injection
- src/config/: ConfigManager class (single source of truth)
- src/services/: Git, OpenAI, prompt services with custom errors
- src/core/: Business logic (commitGenerator, messageBuilder)
- src/utils/: Pure utility functions

Key improvements:
- Eliminate 4 global state variables
- Enable proper unit testing (26 → 57 tests)
- Reduce index.js to 21 lines (thin entry point)
- Add custom error classes for better error handling

Author: ryota-murakami

index.js

@@ -19,6 +19,7 @@
   "files": [
     "README.md",
     "index.js",
+    "src",
     "utils"
   ],
   "author": "Ryota Murakami <dojce1048@gmail.com> (https://github.com/ryota-murakami)",

package.json

@@ -0,0 +1,60 @@
+import { select, password, confirm } from '../../services/prompt.js'
+import { maskApiKey } from '../../utils/maskApiKey.js'
+
+/**
+ * Create the API key management command handler
+ * @param {object} deps - Dependencies
+ * @param {import('../../config/index.js').ConfigManager} deps.config - Config manager
+ * @returns {Function} The command handler
+ */
+export function createApiKeyCommand({ config }) {
+  return async function apiKeyAction() {
+    const actionResponse = await select(
+      'What would you like to do with your OpenAI API key?',
+      [
+        { title: 'Add or update API key', value: 'add' },
+        { title: 'Show API key (masked)', value: 'show' },
+        { title: 'Delete API key', value: 'delete' },
+      ],
+      0,
+    )
+
+    if (!actionResponse) {
+      console.log('Action cancelled.')
+      return
+    }
+
+    switch (actionResponse) {
+      case 'add': {
+        const inputKey = await password('Enter your OpenAI API key')
+        if (inputKey) {
+          config.set('apiKey', inputKey)
+          console.log('API key saved to configuration.')
+        } else {
+          console.log('Action cancelled.')
+        }
+        break
+      }
+
+      case 'delete': {
+        const confirmDelete = await confirm(
+          'Are you sure you want to delete your stored API key?',
+          false,
+        )
+        if (confirmDelete) {
+          config.delete('apiKey')
+          console.log('API key deleted from configuration.')
+        } else {
+          console.log('Action cancelled.')
+        }
+        break
+      }
+
+      case 'show': {
+        const currentKey = config.get('apiKey')
+        console.log(`OpenAI API key: ${maskApiKey(currentKey)}`)
+        break
+      }
+    }
+  }
+}

src/cli/commands/apiKey.js

@@ -0,0 +1,78 @@
+import path from 'path'
+import process from 'process'
+
+import { generateCommitMessage } from '../../core/commitGenerator.js'
+import { NoChangesError } from '../../services/errors.js'
+import { getStagedDiff, executeCommit } from '../../services/git.js'
+import * as openaiService from '../../services/openai.js'
+import { confirm } from '../../services/prompt.js'
+
+/**
+ * Load API key from environment if not in config
+ * @param {string|null} configApiKey - API key from config
+ * @returns {Promise<string|null>} The API key
+ */
+async function resolveApiKey(configApiKey) {
+  if (configApiKey) return configApiKey
+
+  // Try to load from .env
+  const dotenv = await import('dotenv')
+  const envPath = path.join(process.cwd(), '.env')
+  dotenv.config({ path: envPath })
+
+  return process.env.OPENAI_API_KEY || null
+}
+
+/**
+ * Create the commit command handler
+ * @param {object} deps - Dependencies
+ * @param {import('../../config/index.js').ConfigManager} deps.config - Config manager
+ * @returns {Function} The command handler
+ */
+export function createCommitCommand({ config }) {
+  return async function commitAction() {
+    try {
+      // Get staged diff
+      const diff = await getStagedDiff()
+
+      // Resolve API key
+      const apiKey = await resolveApiKey(config.get('apiKey'))
+      if (!apiKey) {
+        console.error(
+          'No OpenAI API key found. Please set it using "git gpt open-api-key add".',
+        )
+        process.exit(1)
+      }
+
+      // Create OpenAI client
+      const client = openaiService.createClient(apiKey)
+
+      // Generate commit message
+      const message = await generateCommitMessage(
+        { openaiService, client },
+        {
+          diff,
+          model: config.get('model'),
+          language: config.get('language'),
+          prefixEnabled: config.get('prefixEnabled'),
+        },
+      )
+
+      // Confirm with user
+      const confirmed = await confirm(`${message}.`)
+      if (confirmed) {
+        executeCommit(message)
+        console.log('Committed with the suggested message.')
+      } else {
+        console.log('Commit canceled.')
+      }
+    } catch (error) {
+      if (error instanceof NoChangesError) {
+        console.log('No changes to commit. Commit canceled.')
+        process.exit(0)
+      }
+      console.error(error.message)
+      process.exit(1)
+    }
+  }
+}

src/cli/commands/commit.js

@@ -0,0 +1,23 @@
+import { maskApiKey } from '../../utils/maskApiKey.js'
+
+/**
+ * Create the config display command handler
+ * @param {object} deps - Dependencies
+ * @param {import('../../config/index.js').ConfigManager} deps.config - Config manager
+ * @returns {Function} The command handler
+ */
+export function createConfigCommand({ config }) {
+  return function configAction() {
+    const prefixEnabled = config.get('prefixEnabled')
+    const model = config.get('model')
+    const language = config.get('language')
+    const apiKey = config.get('apiKey')
+    const configPath = config.getPath()
+
+    console.log(`  prefix: ${prefixEnabled ? 'enabled' : 'disabled'}`)
+    console.log(`   model: ${model}`)
+    console.log(`    lang: ${language}`)
+    console.log(`  apikey: ${maskApiKey(apiKey)}`)
+    console.log(`    path: ${configPath}`)
+  }
+}

src/cli/commands/config.js

@@ -0,0 +1,6 @@
+export { createCommitCommand } from './commit.js'
+export { createModelCommand } from './model.js'
+export { createLangCommand } from './lang.js'
+export { createPrefixCommand } from './prefix.js'
+export { createApiKeyCommand } from './apiKey.js'
+export { createConfigCommand } from './config.js'

src/cli/commands/index.js

@@ -0,0 +1,25 @@
+import { availableLanguages } from '../../config/defaults.js'
+import { select } from '../../services/prompt.js'
+
+/**
+ * Create the language selection command handler
+ * @param {object} deps - Dependencies
+ * @param {import('../../config/index.js').ConfigManager} deps.config - Config manager
+ * @returns {Function} The command handler
+ */
+export function createLangCommand({ config }) {
+  return async function langAction() {
+    const selectedLanguage = await select(
+      'Select a language for commit messages',
+      availableLanguages,
+      0,
+    )
+
+    if (selectedLanguage) {
+      config.set('language', selectedLanguage)
+      console.log(
+        `Language set to ${selectedLanguage} and saved to configuration`,
+      )
+    }
+  }
+}

src/cli/commands/lang.js

@@ -0,0 +1,19 @@
+import { availableModels } from '../../config/defaults.js'
+import { select } from '../../services/prompt.js'
+
+/**
+ * Create the model selection command handler
+ * @param {object} deps - Dependencies
+ * @param {import('../../config/index.js').ConfigManager} deps.config - Config manager
+ * @returns {Function} The command handler
+ */
+export function createModelCommand({ config }) {
+  return async function modelAction() {
+    const selectedModel = await select('Select a model', availableModels, 0)
+
+    if (selectedModel) {
+      config.set('model', selectedModel)
+      console.log(`Model set to ${selectedModel} and saved to configuration`)
+    }
+  }
+}

src/cli/commands/model.js

@@ -0,0 +1,36 @@
+import { select } from '../../services/prompt.js'
+
+/**
+ * Create the prefix toggle command handler
+ * @param {object} deps - Dependencies
+ * @param {import('../../config/index.js').ConfigManager} deps.config - Config manager
+ * @returns {Function} The command handler
+ */
+export function createPrefixCommand({ config }) {
+  return async function prefixAction() {
+    const currentEnabled = config.get('prefixEnabled')
+
+    // Show current state
+    console.log(
+      `Prefixes are currently ${currentEnabled ? 'enabled' : 'disabled'}.`,
+    )
+
+    const choices = [
+      { title: 'Enable prefixes', value: true },
+      { title: 'Disable prefixes', value: false },
+    ]
+
+    const selectedValue = await select(
+      'Set commit message prefixes (e.g., fix:, feat:, refactor:)',
+      choices,
+      currentEnabled ? 0 : 1,
+    )
+
+    if (selectedValue !== undefined) {
+      config.set('prefixEnabled', selectedValue)
+      console.log(
+        `Prefix ${selectedValue ? 'enabled' : 'disabled'} and saved to configuration`,
+      )
+    }
+  }
+}

src/cli/commands/prefix.js

@@ -0,0 +1,80 @@
+import { program } from 'commander'
+
+import { ConfigManager } from '../config/index.js'
+
+import {
+  createCommitCommand,
+  createModelCommand,
+  createLangCommand,
+  createPrefixCommand,
+  createApiKeyCommand,
+  createConfigCommand,
+} from './commands/index.js'
+
+/**
+ * Setup and run the CLI
+ * @param {object} [options] - Options
+ * @param {ConfigManager} [options.config] - Config manager instance (for testing)
+ */
+export function setupCli(options = {}) {
+  // Use provided config or create new one
+  const config = options.config || new ConfigManager()
+
+  // Load configuration at startup
+  config.load()
+
+  // Create command handlers with dependencies
+  const deps = { config }
+
+  // Register commands
+  program
+    .command('commit')
+    .description(
+      'Generate a Git commit message based on the summary of changes',
+    )
+    .action(createCommitCommand(deps))
+
+  program
+    .command('model')
+    .description('Select the model to use')
+    .action(createModelCommand(deps))
+
+  program
+    .command('lang')
+    .description('Select the commit message language')
+    .action(createLangCommand(deps))
+
+  program
+    .command('prefix')
+    .description('Toggle commit message prefix (e.g., fix:, feat:, refactor:)')
+    .action(createPrefixCommand(deps))
+
+  program
+    .command('open-api-key')
+    .description('Manage your OpenAI API key')
+    .action(createApiKeyCommand(deps))
+
+  program
+    .command('config')
+    .description('Show current configuration')
+    .action(createConfigCommand(deps))
+
+  // Handle invalid commands
+  program.on('command:*', () => {
+    console.error('Invalid command: %s\n', program.args.join(' '))
+    program.help()
+  })
+
+  return program
+}
+
+/**
+ * Main entry point for the CLI
+ * @param {string[]} [args] - Command line arguments
+ */
+export function runCli(args = process.argv) {
+  const program = setupCli()
+  program.parse(args)
+}
+
+export default runCli