todo_app.py

# To-Do List Application - Codveda Internship Level 2 Task 1
# Command-line task manager with JSON storage and filtering

import json
import os
from datetime import date

TASKS_FILE = "tasks.json"


def load_tasks():
    """Load tasks from the JSON file. Returns an empty list if the file doesn't exist yet."""
    if not os.path.exists(TASKS_FILE):
        return []
    with open(TASKS_FILE, "r") as f:
        try:
            data = json.load(f)
        except json.JSONDecodeError:
            print("Warning: tasks file was corrupted. Starting fresh.")
            data = []
    return data


def save_tasks(tasks):
    """Write the full task list back to the JSON file."""
    with open(TASKS_FILE, "w") as f:
        json.dump(tasks, f, indent=2)


def next_id(tasks):
    """Figure out the next available ID based on what's already in the list."""
    if not tasks:
        return 1
    return max(task["id"] for task in tasks) + 1


# ---- Add a task ----

def add_task(tasks):
    title = input("Task title: ").strip()
    if not title:
        print("Title can't be empty.")
        return

    new_task = {
        "id": next_id(tasks),
        "title": title,
        "status": "pending",
        "created": str(date.today())
    }

    tasks.append(new_task)
    save_tasks(tasks)
    print(f"Added: \"{title}\"")


# ---- View tasks ----

def display_tasks(task_list):
    """Print a formatted list of tasks. Used by both view_all and filtered views."""
    if not task_list:
        print("  No tasks to show.")
        return

    # figure out the longest title so we can line things up
    max_title = max(len(t["title"]) for t in task_list)
    max_title = max(max_title, 5)  # minimum width

    print(f"  {'ID':<5} {'Title':<{max_title + 2}} {'Status':<10} {'Created'}")
    print("  " + "-" * (max_title + 32))

    for t in task_list:
        # put a checkmark next to completed tasks
        status_display = "done" if t["status"] == "done" else "pending"
        mark = "  [x]" if t["status"] == "done" else "  [ ]"
        print(f"{mark} {t['id']:<5} {t['title']:<{max_title + 2}} {status_display:<10} {t['created']}")


def view_tasks(tasks):
    if not tasks:
        print("\nYour to-do list is empty. Add some tasks first!")
        return

    print("\n-- All Tasks --")
    display_tasks(tasks)


# ---- Mark a task as done ----

def mark_done(tasks):
    if not tasks:
        print("No tasks to mark.")
        return

    # show pending tasks so the user knows what's available
    pending = [t for t in tasks if t["status"] == "pending"]
    if not pending:
        print("All tasks are already completed!")
        return

    print("\nPending tasks:")
    for t in pending:
        print(f"  ID {t['id']}: {t['title']}")

    raw = input("Enter the task ID to mark as done: ").strip()

    try:
        task_id = int(raw)
    except ValueError:
        print("That's not a valid ID.")
        return

    # look for the task
    for t in tasks:
        if t["id"] == task_id:
            if t["status"] == "done":
                print(f"\"{t['title']}\" is already marked as done.")
            else:
                t["status"] = "done"
                save_tasks(tasks)
                print(f"Marked \"{t['title']}\" as done!")
            return

    print(f"No task found with ID {task_id}.")


# ---- Delete a task ----

def delete_task(tasks):
    if not tasks:
        print("Nothing to delete.")
        return

    print("\nCurrent tasks:")
    for t in tasks:
        status_tag = " (done)" if t["status"] == "done" else ""
        print(f"  ID {t['id']}: {t['title']}{status_tag}")

    raw = input("Enter the task ID to delete: ").strip()

    try:
        task_id = int(raw)
    except ValueError:
        print("That's not a valid ID.")
        return

    # find and remove
    for i, t in enumerate(tasks):
        if t["id"] == task_id:
            removed = tasks.pop(i)
            save_tasks(tasks)
            print(f"Deleted \"{removed['title']}\".")
            return

    print(f"No task found with ID {task_id}.")


# ---- Main menu loop ----

def main():
    tasks = load_tasks()

    print("\n===== To-Do List Manager =====")

    while True:
        # count pending for the menu header
        pending_count = sum(1 for t in tasks if t["status"] == "pending")
        total = len(tasks)

        print(f"\n--- Menu --- ({pending_count} pending / {total} total)")
        print("1. Add a task")
        print("2. View tasks")
        print("3. Mark task as done")
        print("4. Delete a task")
        print("5. Quit")

        choice = input("\nPick an option (1-5): ").strip()

        if choice == "1":
            add_task(tasks)
        elif choice == "2":
            view_tasks(tasks)
        elif choice == "3":
            mark_done(tasks)
        elif choice == "4":
            delete_task(tasks)
        elif choice == "5":
            print("Goodbye! Your tasks are saved.")
            break
        else:
            print("Not a valid option. Try 1 through 5.")


main()