Putting It All Together

Part of the Introduction To Luau section of Coddy's Lua journey. Lesson 50 of 73.

Challenge

Medium

Your editor already contains the complete toolkit: the Task type, the tasks array (three starter tasks), addTask, completeTask, filterTasks and printSummary.

Write a command loop that keeps reading a line with io.read() and handles these commands:

add — read one more line as the title, call addTask, and print exactly: Added task {id}: {title} (using the returned task's fields)
done — read one more line, convert it with tonumber(...) or 0, call completeTask; print Task {id} completed if it returned true, otherwise No task with id {id}
list — for every task, print [x] {title} if it's done, otherwise [ ] {title} (note the space)
pending — print the title of every unfinished task, using filterTasks
summary — call printSummary(tasks)
quit — stop the loop (also stop if io.read() returns nil)

Try it yourself

-- The shape every task in the manager must follow
type Task = {
    id: number,
    title: string,
    done: boolean,
}

-- The task list: a typed array of Task shapes
local tasks: {Task} = {
    {id = 1, title = "Learn Luau types", done = false},
    {id = 2, title = "Build a task manager", done = false},
    {id = 3, title = "Write tests", done = true},
}

-- Build a typed task with the next free id and insert it
local function addTask(list: {Task}, title: string): Task
    local newTask: Task = {
        id = #list + 1,
        title = title,
        done = false,
    }
    table.insert(list, newTask)
    return newTask
end

-- Mark the task with the given id as done; report success
local function completeTask(list: {Task}, id: number): boolean
    for _, t in ipairs(list) do
        if t.id == id then
            t.done = true
            return true
        end
    end
    return false
end

-- Collect the tasks whose done flag matches into a new {Task}
local function filterTasks(list: {Task}, done: boolean): {Task}
    local result: {Task} = {}
    for _, t in ipairs(list) do
        if t.done == done then
            table.insert(result, t)
        end
    end
    return result
end

-- Print a one-line progress summary
local function printSummary(list: {Task}): ()
    local total = #list
    local doneCount = 0
    for _, t in ipairs(list) do
        if t.done then
            doneCount = doneCount + 1
        end
    end
    print(`{doneCount}/{total} tasks done`)
end

-- Watch the summary change as the list evolves
printSummary(tasks)
completeTask(tasks, 2)
printSummary(tasks)
addTask(tasks, "Take a break")
printSummary(tasks)