const electron = require('electron')
const path = require('path')
const fs = require('fs')

class Store {
    
    constructor(opts) {

        // Renderer process has to get `app` module via `remote`, whereas the main process can get it directly
        // app.getPath('userData') will return a string of the user's app data directory path.
        const userDataPath = (electron.app || electron.remote.app).getPath('userData')
        // We'll use the `configName` property to set the file name and path.join to bring it all together as a string
        this.path = path.join(userDataPath, opts.configName + '.json')
        
        this.data = parseDataFile(this.path, opts.defaults)
        this.data = Object.assign(opts.defaults, this.data)
    }
    
    // This will just return the property on the `data` object
    get(key) {
        return this.data[key]
    }
    
    // ...and this will set it
    set(key, val) {
        this.data[key] = val
        // Wait, I thought using the node.js' synchronous APIs was bad form?
        // We're not writing a server so there's not nearly the same IO demand on the process
        // Also if we used an async API and our app was quit before the asynchronous write had a chance to complete,
        // we might lose that data. Note that in a real app, we would try/catch this.
        fs.writeFileSync(this.path, JSON.stringify(this.data))
    }
}

function parseDataFile(filePath, defaults) {
    // We'll try/catch it in case the file doesn't exist yet, which will be the case on the first application run.
    // `fs.readFileSync` will return a JSON string which we then parse into a Javascript object
    try {
        return JSON.parse(fs.readFileSync(filePath))
    } catch(error) {
        // if there was some kind of error, return the passed in defaults instead.
        return defaults
    }
}

// expose the class
module.exports = Store