use crate::{CurrentTaskInfo, Task};

use std::cmp::Ordering;
use std::io::Write;
use std::path::PathBuf;

#[derive(clap::Args)]
pub struct Args {
    idx: usize,
    #[clap(subcommand)]
    priority: Priority,
}

#[derive(clap::Subcommand)]
pub enum Priority {
    Before { idx: usize },
    After { idx: usize },
}

pub struct Request {
    pub args: Args,
    pub tasks: Vec<Task>,
    pub current_task_info: Option<CurrentTaskInfo>,
    pub tasks_file_path: PathBuf,
}

pub fn execute(mut req: Request) {
    if req.current_task_info.is_some() {
        panic!("You can change priority only when you don't have an active task, yet");
    }

    let target_idx = req.args.idx;
    if target_idx == 0 || target_idx > req.tasks.len() {
        panic!("invalid index");
    }

    let idx = match req.args.priority {
        Priority::Before { idx } | Priority::After { idx } => match target_idx.cmp(&idx) {
            Ordering::Equal => return,
            Ordering::Less => idx - 1,
            Ordering::Greater => idx,
        },
    };
    if idx == 0 || idx > req.tasks.len() {
        panic!("invalid index");
    }

    let target = req.tasks.remove(target_idx - 1);

    match req.args.priority {
        Priority::Before { .. } => {
            req.tasks.insert(idx - 1, target);
        }
        Priority::After { .. } => {
            req.tasks.insert(idx, target);
        }
    }

    let mut file = std::fs::File::create(&req.tasks_file_path).unwrap();
    file.write_all(&serde_json::to_vec(&req.tasks).unwrap())
        .unwrap();
}