use chrono::{Date, Datelike, Duration, Local};
use enigo::*;
use std::env;
use std::process;
use std::{thread, time};

#[cfg(test)]
use chrono::prelude::*;

fn command_to_date(command: &str) -> Result<Date<Local>, ()> {
    let today = Local::today();
    calc_date(command, today)
}

fn calc_date(command: &str, today: Date<Local>) -> Result<Date<Local>, ()> {
    let offset = if command == "today" {
        Ok(0)
    } else if command == "tomorrow" {
        Ok(1)
    } else if command == "yesterday" {
        Ok(-1)
    } else if command == "daybeforeyesterday" {
        Ok(-2)
    } else if command == "dayaftertomorrow" {
        Ok(2)
    } else if command.starts_with("next") || command.starts_with("last") {
        let wday = today.weekday().num_days_from_monday() as i64;
        let target = match &command[4..] {
            "monday" => Ok(0),
            "tuesday" => Ok(1),
            "wednesday" => Ok(2),
            "thursday" => Ok(3),
            "friday" => Ok(4),
            "saturday" => Ok(5),
            "sunday" => Ok(6),
            _ => Err(()),
        };

        if let Ok(target) = target {
            if command.starts_with("next") {
                Ok((target - wday + 7 - 1) % 7 + 1)
            } else {
                Ok(-((wday - target + 7 - 1) % 7 + 1))
            }
        } else {
            Err(())
        }
    } else {
        return Err(());
    };

    if let Ok(offset) = offset {
        return Ok(today + Duration::days(offset));
    }
    Err(())
}

fn type_date(date: Date<Local>, alt_tab: bool, enter: bool) {
    let date_str = format!("{}", date.format("%Y-%m-%d"));
    let mut enigo = Enigo::new();
    if alt_tab {
        enigo.key_down(Key::Alt);
        enigo.key_click(Key::Tab);
        enigo.key_up(Key::Alt);
        thread::sleep(time::Duration::from_millis(100));
    }

    for c in date_str.chars() {
        enigo.key_click(Key::Layout(c));
    }

    if enter {
        enigo.key_click(Key::Return);
    }
}

fn main() {
    let mut command = String::new();
    let mut alt_tab = false;
    let mut enter = false;

    for arg in env::args().skip(1) {
        if arg == "--tab" {
            alt_tab = true;
        } else if arg == "--enter" {
            enter = true;
        } else {
            command = arg.to_lowercase();
            break;
        }
    }

    if let Ok(date) = command_to_date(&command) {
        type_date(date, alt_tab, enter);
    } else {
        eprintln!("blinddate");
        eprintln!("Calculates a date and types it. Use with a shell script to enter dates into files rapidly.");
        eprintln!("Usage: blinddate <command>");
        eprintln!("Supported commands:");
        eprintln!("  today");
        eprintln!("  tomorrow");
        eprintln!("  yesterday");
        eprintln!("  daybeforeyesterday");
        eprintln!("  dayaftertomorrow");
        eprintln!("  next<weekday> (e.g. nextmonday)");
        eprintln!("  last<weekday> (e.g. lastsaturday)");
        process::exit(1);
    }
}

#[test]
fn test_calc_date() {
    let today = Local.ymd(2020, 9, 1);
    assert!(Local.ymd(2020, 9, 1) == calc_date("today", today).unwrap());
    assert!(Local.ymd(2020, 9, 2) == calc_date("tomorrow", today).unwrap());
    assert!(Local.ymd(2020, 8, 31) == calc_date("yesterday", today).unwrap());
    assert!(Local.ymd(2020, 8, 30) == calc_date("daybeforeyesterday", today).unwrap());
    assert!(Local.ymd(2020, 9, 3) == calc_date("dayaftertomorrow", today).unwrap());
    assert!(Local.ymd(2020, 9, 7) == calc_date("nextmonday", today).unwrap());
    assert!(Local.ymd(2020, 9, 8) == calc_date("nexttuesday", today).unwrap());
    assert!(Local.ymd(2020, 9, 2) == calc_date("nextwednesday", today).unwrap());
    assert!(Local.ymd(2020, 9, 3) == calc_date("nextthursday", today).unwrap());
    assert!(Local.ymd(2020, 9, 4) == calc_date("nextfriday", today).unwrap());
    assert!(Local.ymd(2020, 9, 5) == calc_date("nextsaturday", today).unwrap());
    assert!(Local.ymd(2020, 9, 6) == calc_date("nextsunday", today).unwrap());
    assert!(Local.ymd(2020, 8, 31) == calc_date("lastmonday", today).unwrap());
    assert!(Local.ymd(2020, 8, 25) == calc_date("lasttuesday", today).unwrap());
    assert!(Local.ymd(2020, 8, 26) == calc_date("lastwednesday", today).unwrap());
    assert!(Local.ymd(2020, 8, 27) == calc_date("lastthursday", today).unwrap());
    assert!(Local.ymd(2020, 8, 28) == calc_date("lastfriday", today).unwrap());
    assert!(Local.ymd(2020, 8, 29) == calc_date("lastsaturday", today).unwrap());
    assert!(Local.ymd(2020, 8, 30) == calc_date("lastsunday", today).unwrap());
    assert!(calc_date("weirdbullshit", today).is_err());
}