use crate::queries::*;
use sqlite::*;
use std::fs::{self, OpenOptions};
use std::io;
use std::path::{Path, PathBuf};

/// Return the default path to the datasets file.
fn default_datasets_path(config_dir: &Path) -> io::Result<PathBuf> {
    let mut path = config_dir.to_owned();
    path.push("ggelo");

    // Create datasets path if it doesn't exist
    fs::create_dir_all(&path)?;

    path.push("ggelo.db");

    // Create datasets file if it doesn't exist
    OpenOptions::new().write(true).create(true).open(&path)?;

    Ok(path)
}

pub fn open_datasets(config_dir: &Path, path: Option<&Path>) -> sqlite::Result<Connection> {
    let path = path.map_or_else(
        || default_datasets_path(config_dir).unwrap(),
        |p| p.to_owned(),
    );

    let query = "
        CREATE TABLE IF NOT EXISTS datasets (
            name TEXT UNIQUE NOT NULL
        ) STRICT;
    ";

    let connection = sqlite::open(path)?;
    connection.execute(query)?;
    Ok(connection)
}

// TODO: Sanitize dataset names

pub fn list_datasets(connection: &Connection) -> sqlite::Result<Vec<String>> {
    let query = "SELECT * FROM datasets";

    connection
        .prepare(query)?
        .into_iter()
        .map(|x| x.map(|r| r.read::<&str, _>("name").to_owned()))
        .try_collect()
}

pub fn new_dataset(connection: &Connection, dataset: &str) -> sqlite::Result<()> {
    let query = format!(
        "
        INSERT INTO datasets VALUES ('{0}');

        CREATE TABLE IF NOT EXISTS \"dataset_{0}\" (
            id INTEGER PRIMARY KEY,
            name TEXT,
            prefix TEXT,
            elo REAL NOT NULL
        ) STRICT;
    ",
        dataset
    );

    connection.execute(query)
}

// Score calculation

/// Calculate the collective expected score for each team.
fn expected_scores(ratings: &Teams<&mut f64>) -> Vec<f64> {
    let qs: Vec<f64> = ratings
        .into_iter()
        .map(|es| 10_f64.powf(es.iter().map(|x| **x).sum::<f64>() / es.len() as f64 / 400.0))
        .collect();
    let sumq: f64 = qs.iter().sum();
    qs.into_iter().map(|q| q / sumq).collect()
}

/// Adjust the ratings of each player based on who won.
fn adjust_ratings(ratings: Teams<&mut f64>, winner: usize) {
    let exp_scores = expected_scores(&ratings);

    ratings
        .into_iter()
        .zip(exp_scores.into_iter())
        .enumerate()
        .for_each(|(i, (es, exp_sc))| {
            let len = es.len() as f64;
            let score = f64::from(winner == i);
            es.into_iter()
                .for_each(|e| *e += 40.0 * (score - exp_sc) / len);
        })
}

// Database Updating

pub fn add_players(
    connection: &Connection,
    dataset: &str,
    teams: &Teams<PlayerData>,
) -> sqlite::Result<()> {
    let query = format!(
        "INSERT OR IGNORE INTO \"dataset_{}\" VALUES (?, ?, ?, 1500)",
        dataset
    );

    teams.iter().try_for_each(|team| {
        team.iter().try_for_each(|PlayerData { id, name, prefix }| {
            let mut statement = connection.prepare(&query)?;
            statement.bind((1, id.0 as i64))?;
            statement.bind((2, name.as_ref().map(|x| &x[..])))?;
            statement.bind((3, prefix.as_ref().map(|x| &x[..])))?;
            statement.into_iter().try_for_each(|x| x.map(|_| ()))
        })
    })
}

pub fn get_ratings(
    connection: &Connection,
    dataset: &str,
    teams: &Teams<PlayerData>,
) -> sqlite::Result<Teams<(PlayerId, f64)>> {
    let query = format!("SELECT id, elo FROM \"dataset_{}\" WHERE id = ?", dataset);

    teams
        .iter()
        .map(|team| {
            team.iter()
                .map(|data| {
                    let mut statement = connection.prepare(&query)?;
                    statement.bind((1, data.id.0 as i64))?;
                    statement.next()?;
                    Ok((data.id, statement.read::<f64, _>("elo")?))
                })
                .try_collect()
        })
        .try_collect()
}

pub fn update_ratings(
    connection: &Connection,
    dataset: &str,
    elos: Teams<(PlayerId, f64)>,
) -> sqlite::Result<()> {
    let query = format!(
        "UPDATE \"dataset_{}\" SET elo = :elo WHERE id = :id",
        dataset
    );
    elos.into_iter().try_for_each(|team| {
        team.into_iter().try_for_each(|(id, elo)| {
            let mut statement = connection.prepare(&query)?;
            statement.bind((":elo", elo))?;
            statement.bind((":id", id.0 as i64))?;
            statement.into_iter().try_for_each(|x| x.map(|_| ()))
        })
    })
}

pub fn update_from_set(
    connection: &Connection,
    dataset: &str,
    results: SetData,
) -> sqlite::Result<()> {
    let players_data = results.teams;
    add_players(connection, dataset, &players_data)?;

    let mut elos = get_ratings(connection, dataset, &players_data)?;
    adjust_ratings(
        elos.iter_mut()
            .map(|v| v.iter_mut().map(|x| &mut x.1).collect())
            .collect(),
        results.winner,
    );
    update_ratings(connection, dataset, elos)
}