[面包]MrTwoC

Add=>
 command_add()=> receives user input, checks if the first parameter is add, then checks the parameter length; if parameters < 3, it prompts insufficient parameters,
then calls Target::add()=> method to receive four parameters, including <task name><due date>[description][group], with [] as optional parameters,
so you only need to input the task name and date to add a task, other parameters will be set to default values.
Before adding, it will first traverse all task IDs in the file, then +1 for the new task, and then write to json.
                                           
Delete=>
Read the json file, define a variable to store the length, call the .retain method, which works=>
Traverse each element in the tasks vector
For each element, execute the closure |task| task.id != Some(id)
Retain elements that return true from the closure, remove elements that return false.
Then compare the length before and after deletion; if it is less than the previous length, the deletion was successful.
                                           
Query=>
Read json and then traverse.

Edit=>
Receives user input, checks if the command length < 3 or (command length - 1) % 2 == 0, it will prompt mismatch because the 0th and 1st are edit and task ID,
2 is the field name, and 2+1 is the modification content, so it can match like this, then enter Target::edit()=> method.
Checks if the id is valid and exists, then retrieves the task by id, enters a for loop, defines two variables: field and parameter, enters match to match the field,
if matched, modifies it, then writes to the json file.
// Get mutable task reference
        let task = &mut tasks[task_index];

        // Parse and apply field updates (starting from index 1, every two parameters form a group)
        for i in (2..args.len()).step_by(2) {
            let field = args[i];
            let value = args[i + 1];

            // Task status can be modified separately
            match field {
                "name" => task.target_name = value.to_string(),
                "deadline" => task.deadline = value.to_string(),
                "description" => task.description = Some(value.to_string()),
                "group" => task.group = Some(value.to_string()),

                _ => eprintln!("Unsupported field: {}", field),
            }
        }