Task Manager (todo list) using Linked List

I want to create a Task Manager application in C. This application will manage a list of tasks, allowing users to add, remove, display, save, and load tasks from a file. Each task will have a description and a status (e.g., pending or completed). The application will utilize a linked list to manage tasks dynamically, ensuring efficient memory usage and easy management of tasks.

Design Decisions

I would go for enum over boolean for task's state as it's going to be more fun and I can use colors for each state.

So here's the enum for task's state:

typedef enum
{
    NOT_STARTED,
    ON_GOING,
    DONE,
    CANCELLED,
} TaskState;

Here's the Task struct and the Linked List:

typedef struct Task
{
    unsigned long long id;
    char* description;
    TaskState state;
    struct Task* next;
} Task;

typedef struct
{
    Task* head;
    Task* tail;
    size_t size;
} TodoList;

NOTE: I would use a unique id generator based on date and time in an unsigned long long number field to address tasks instead of searching and comparing the descriptions.

Introducing memory check and improving Makefile

It's a good time to use the good old friend valgrind as this project involves various memory allocations and de-allocations. also as using valgrind needs debug symbols to be available -g then I thought "well, I might want to have my executable optimized" so with that in mind, I've tweaked and improved my Makefile to support for these new targets: release, memcheck.

The obj folder now holds object files for different targets (debug and release) separately, the default build is for sure debug that is built into all target.

Running make memcheck ensures that I've got no memory leaked:

valgrind --leak-check=yes build/todo_c.exe
==20928== Memcheck, a memory error detector
==20928== Copyright (C) 2002-2024, and GNU GPL'd, by Julian Seward et al.
==20928== Using Valgrind-3.23.0 and LibVEX; rerun with -h for copyright info
==20928== Command: build/todo_c.exe
==20928== 
Todo list contents:
ID: 20240728085122, I go to school
ID: 20240728085123, I go to gym
ID: 20240728085124, I go everywhere!
task deleted successfully
Todo list contents after deletion:
ID: 20240728085123, I go to gym
ID: 20240728085124, I go everywhere!
==20928== 
==20928== HEAP SUMMARY:
==20928==     in use at exit: 0 bytes in 0 blocks
==20928==   total heap usage: 15 allocs, 15 frees, 6,489 bytes allocated
==20928== 
==20928== All heap blocks were freed -- no leaks are possible
==20928== 
==20928== For lists of detected and suppressed errors, rerun with: -s
==20928== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

Dealing with data

I want to make this a command line tool something with various commands that uses a specific file close to itself to save and load data:

• list lists all the data if there is no file available or there is no entry it returns No Entry - please use 'add' command to add new task
• add this commands receives a description which must be sent inside double quotes, then it generates a new entry and returns the task id as well. one other option can be to list the tasks all and highlight the newly created task which is more fun so I will go for this.
• state sets the state of the given task id to the given state: 0 is not started, 1 is on going, 2 is done and 3 is cancelled. any other values or wrong task id will show proper error messages.
• delete gets task id and delete it while returns its last content including id, description and state.

NOTE: Not only after adding a new task but after each operation the overall list of tasks will be displayed.

NOTE2: I would also to colorize task's state like one specific color per state.

NOTE3: I will use background color for the newly added or changed tasks.

License

Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) License.

Please refer to LICENSE file.