use serenity::framework::standard::{macros::command, Args, CommandResult};
use serenity::model::prelude::*;
use serenity::prelude::*;

use std::fs::File;
use std::io::Read;
use serde_json::Value;

use rand::seq::IteratorRandom;

fn random_from_string(string: &str) -> char {
    string.chars().choose(&mut rand::thread_rng()).unwrap()
}

async fn display_kanji(ctx: &Context, msg: &Message, kanji: char, comment: &str) -> CommandResult {
    msg.reply(&ctx.http, format!(":game_die: {}{}", kanji, comment)).await?;
    let url = format!("https://raw.githubusercontent.com/mistval/kanji_images/master/gifs/{}.gif", format!("{:x}", kanji as i32));
    let response = reqwest::get(&url)
        .await?
        .text()
        .await?;
    msg.channel_id.say(&ctx.http, if response == "404: Not Found" {
        "The stroke order diagram for this kanji is unavailable."
    } else { &url }).await?;
    Ok(())
}

async fn random_kanji(category: &str, ctx: &Context, msg: &Message, mut args: Args) -> CommandResult {
    let mut lists_file = File::open("kanji_lists.json").unwrap();
    let mut lists_json = String::new();
    lists_file.read_to_string(&mut lists_json).unwrap();
    let lists_data: Value = serde_json::from_str(&lists_json).unwrap();
    let category = &lists_data[category];
    let default_version = category["default"].as_str().unwrap();
    let list = &category["versions"][default_version]["characters"];
    match list.as_str() {
        Some(string) => {
            let kanji = random_from_string(string);
            display_kanji(&ctx, &msg, kanji, "").await?;
        },
        None => {
            let subcategory = args.single::<String>();
            let subcategories = list.as_object().unwrap();
            let subcategory_list = {
                let mut string = String::from("\n");
                let mut total_count = 0;
                for subcategory in subcategories.keys() {
                    let subcategory = subcategory.as_str();
                    // One has to do .chars().count() as opposed to .len() here,
                    // because .len() returns the byte length NOT the number of characters.
                    // For kanji, they are always multi-byte Unicode characters.
                    let count = &subcategories[subcategory].as_str().unwrap().chars().count();
                    total_count += count;
                    string.push_str(&format!("**{}** ({} kanji),\n", subcategory, count));
                }
                string.push_str(&format!("or **all** ({} kanji total) for all subcategories", total_count));
                string
            };
            match subcategory {
                Ok(string) => {
                    let string = string.to_uppercase();
                    if string == "ALL" {
                        let subcategory_key = subcategories.keys().choose(&mut rand::thread_rng()).unwrap();
                        let list = subcategories[subcategory_key].as_str().unwrap();
                        let kanji = random_from_string(&list);
                        display_kanji(&ctx, &msg, kanji, &format!(", **{}**", subcategory_key)).await?;
                    } else if subcategories.contains_key(&string) {
                        let list = list[&string].as_str().unwrap();
                        let kanji = random_from_string(&list);
                        display_kanji(&ctx, &msg, kanji, "").await?;
                    } else {
                        let message = format!("That is an invalid subcategory. Please use {}.", &subcategory_list);
                        msg.reply(&ctx.http, message).await?;
                    }
                },
                Err(_) => {
                    let mut message = String::from("Please specify a subcategory: ");
                    message.push_str(&subcategory_list);
                    msg.reply(&ctx.http, message).await?;
                }
            }
        }
    }
    Ok(())
}

#[command]
async fn joyo(ctx: &Context, msg: &Message, args: Args) -> CommandResult {
    random_kanji("JOYO", ctx, msg, args).await
}

#[command]
async fn jinmeiyo(ctx: &Context, msg: &Message, args: Args) -> CommandResult {
    random_kanji("JINMEIYO", ctx, msg, args).await
}

#[command]
async fn kyoiku(ctx: &Context, msg: &Message, args: Args) -> CommandResult {
    random_kanji("KYOIKU", ctx, msg, args).await
}

#[command]
async fn jlpt(ctx: &Context, msg: &Message, args: Args) -> CommandResult {
    random_kanji("JLPT", ctx, msg, args).await
}

#[command]
async fn hyogai(ctx: &Context, msg: &Message, args: Args) -> CommandResult {
    random_kanji("HYOGAI", ctx, msg, args).await
}