userSchema.virtual('tasks', {
    ref: 'Task',
    localField: '_id',
    foreignField: 'owner'
})

userSchema.methods.toJSON = function () {
    const user = this
    const userObject = user.toObject()

    delete userObject.password
    delete userObject.tokens
    delete userObject.avatar

    return userObject
}

userSchema.methods.generateAuthToken = async function () {
    const user = this
    const token = jwt.sign({ _id: user._id.toString() }, process.env.JWT_SECRET)

    user.tokens = user.tokens.concat({ token })
    await user.save()

    return token
}

userSchema.statics.findByCredentials = async (email, password) => {
    const user = await User.findOne({ email })

    if (!user) {
        throw new Error('Unable to login')
    }

    const isMatch = await bcrypt.compare(password, user.password)

    if (!isMatch) {
        throw new Error('Unable to login')
    }

    return user
}

// Hash the plain text password before saving
userSchema.pre('save', async function (next) {
    const user = this

    if (user.isModified('password')) {
        user.password = await bcrypt.hash(user.password, 8)
    }

    next()
})

// Delete user tasks when user is removed
userSchema.pre('remove', async function (next) {
    const user = this
    await Task.deleteMany({ owner: user._id })
    next()
})