use bytes::{Buf, BufMut, BytesMut};
use log::{info, trace};
use tokio::net::tcp::OwnedWriteHalf;

use std::collections::HashMap;

use crate::config::{get_config, parse};
use crate::errors::Error;
use crate::messages::*;
use crate::pool::ConnectionPool;
use crate::stats::get_stats;

/// Handle admin client
pub async fn handle_admin(
    stream: &mut OwnedWriteHalf,
    mut query: BytesMut,
    pool: ConnectionPool,
) -> Result<(), Error> {
    let code = query.get_u8() as char;

    if code != 'Q' {
        return Err(Error::ProtocolSyncError);
    }

    let len = query.get_i32() as usize;
    let query = String::from_utf8_lossy(&query[..len - 5])
        .to_string()
        .to_ascii_uppercase();

    trace!("Admin query: {}", query);

    if query.starts_with("SHOW STATS") {
        trace!("SHOW STATS");
        show_stats(stream).await
    } else if query.starts_with("RELOAD") {
        trace!("RELOAD");
        reload(stream).await
    } else if query.starts_with("SHOW CONFIG") {
        trace!("SHOW CONFIG");
        show_config(stream).await
    } else if query.starts_with("SHOW DATABASES") {
        trace!("SHOW DATABASES");
        show_databases(stream, &pool).await
    } else if query.starts_with("SHOW POOLS") {
        trace!("SHOW POOLS");
        show_pools(stream, &pool).await
    } else if query.starts_with("SHOW LISTS") {
        trace!("SHOW LISTS");
        show_lists(stream, &pool).await
    } else if query.starts_with("SHOW VERSION") {
        trace!("SHOW VERSION");
        show_version(stream).await
    } else if query.starts_with("SET ") {
        trace!("SET");
        ignore_set(stream).await
    } else {
        error_response(stream, "Unsupported query against the admin database").await
    }
}

/// SHOW LISTS
async fn show_lists(stream: &mut OwnedWriteHalf, pool: &ConnectionPool) -> Result<(), Error> {
    let stats = get_stats();

    let columns = vec![("list", DataType::Text), ("items", DataType::Int4)];

    let mut res = BytesMut::new();
    res.put(row_description(&columns));
    res.put(data_row(&vec![
        "databases".to_string(),
        (pool.databases() + 1).to_string(), // see comment below
    ]));
    res.put(data_row(&vec!["users".to_string(), "1".to_string()]));
    res.put(data_row(&vec![
        "pools".to_string(),
        (pool.databases() + 1).to_string(), // +1 for the pgbouncer admin db pool which isn't real
    ])); // but admin tools that work with pgbouncer want this
    res.put(data_row(&vec![
        "free_clients".to_string(),
        stats["cl_idle"].to_string(),
    ]));
    res.put(data_row(&vec![
        "used_clients".to_string(),
        stats["cl_active"].to_string(),
    ]));
    res.put(data_row(&vec![
        "login_clients".to_string(),
        "0".to_string(),
    ]));
    res.put(data_row(&vec![
        "free_servers".to_string(),
        stats["sv_idle"].to_string(),
    ]));
    res.put(data_row(&vec![
        "used_servers".to_string(),
        stats["sv_active"].to_string(),
    ]));
    res.put(data_row(&vec!["dns_names".to_string(), "0".to_string()]));
    res.put(data_row(&vec!["dns_zones".to_string(), "0".to_string()]));
    res.put(data_row(&vec!["dns_queries".to_string(), "0".to_string()]));
    res.put(data_row(&vec!["dns_pending".to_string(), "0".to_string()]));

    res.put(command_complete("SHOW"));

    res.put_u8(b'Z');
    res.put_i32(5);
    res.put_u8(b'I');

    write_all_half(stream, res).await
}

/// SHOW VERSION
async fn show_version(stream: &mut OwnedWriteHalf) -> Result<(), Error> {
    let mut res = BytesMut::new();

    res.put(row_description(&vec![("version", DataType::Text)]));
    res.put(data_row(&vec!["PgCat 0.1.0".to_string()]));
    res.put(command_complete("SHOW"));

    res.put_u8(b'Z');
    res.put_i32(5);
    res.put_u8(b'I');

    write_all_half(stream, res).await
}

/// SHOW POOLS
async fn show_pools(stream: &mut OwnedWriteHalf, _pool: &ConnectionPool) -> Result<(), Error> {
    let stats = get_stats();
    let config = {
        let guard = get_config();
        &*guard.clone()
    };

    let columns = vec![
        ("database", DataType::Text),
        ("user", DataType::Text),
        ("cl_active", DataType::Numeric),
        ("cl_waiting", DataType::Numeric),
        ("cl_cancel_req", DataType::Numeric),
        ("sv_active", DataType::Numeric),
        ("sv_idle", DataType::Numeric),
        ("sv_used", DataType::Numeric),
        ("sv_tested", DataType::Numeric),
        ("sv_login", DataType::Numeric),
        ("maxwait", DataType::Numeric),
        ("maxwait_us", DataType::Numeric),
        ("pool_mode", DataType::Text),
    ];

    let mut res = BytesMut::new();
    res.put(row_description(&columns));

    let mut row = vec![String::from("all"), config.user.name.clone()];

    for column in &columns[2..columns.len() - 1] {
        let value = stats.get(column.0).unwrap_or(&0).to_string();
        row.push(value);
    }

    row.push(config.general.pool_mode.to_string());

    res.put(data_row(&row));
    res.put(command_complete("SHOW"));

    res.put_u8(b'Z');
    res.put_i32(5);
    res.put_u8(b'I');

    write_all_half(stream, res).await
}

/// SHOW DATABASES
async fn show_databases(stream: &mut OwnedWriteHalf, pool: &ConnectionPool) -> Result<(), Error> {
    let guard = get_config();
    let config = &*guard.clone();
    drop(guard);

    // Columns
    let columns = vec![
        ("name", DataType::Text),
        ("host", DataType::Text),
        ("port", DataType::Text),
        ("database", DataType::Text),
        ("force_user", DataType::Text),
        ("pool_size", DataType::Int4),
        ("min_pool_size", DataType::Int4),
        ("reserve_pool", DataType::Int4),
        ("pool_mode", DataType::Text),
        ("max_connections", DataType::Int4),
        ("current_connections", DataType::Int4),
        ("paused", DataType::Int4),
        ("disabled", DataType::Int4),
    ];

    let mut res = BytesMut::new();

    // RowDescription
    res.put(row_description(&columns));

    for shard in 0..pool.shards() {
        let database_name = &config.shards[&shard.to_string()].database;

        for server in 0..pool.servers(shard) {
            let address = pool.address(shard, server);
            let pool_state = pool.pool_state(shard, server);

            res.put(data_row(&vec![
                address.name(),                       // name
                address.host.to_string(),             // host
                address.port.to_string(),             // port
                database_name.to_string(),            // database
                config.user.name.to_string(),         // force_user
                config.general.pool_size.to_string(), // pool_size
                "0".to_string(),                      // min_pool_size
                "0".to_string(),                      // reserve_pool
                config.general.pool_mode.to_string(), // pool_mode
                config.general.pool_size.to_string(), // max_connections
                pool_state.connections.to_string(),   // current_connections
                "0".to_string(),                      // paused
                "0".to_string(),                      // disabled
            ]));
        }
    }

    res.put(command_complete("SHOW"));

    // ReadyForQuery
    res.put_u8(b'Z');
    res.put_i32(5);
    res.put_u8(b'I');

    write_all_half(stream, res).await
}

/// Ignore any SET commands the client sends.
/// This is common initialization done by ORMs.
async fn ignore_set(stream: &mut OwnedWriteHalf) -> Result<(), Error> {
    custom_protocol_response_ok(stream, "SET").await
}

/// RELOAD
async fn reload(stream: &mut OwnedWriteHalf) -> Result<(), Error> {
    info!("Reloading config");

    let config = get_config();
    let path = config.path.clone().unwrap();

    parse(&path).await?;

    let config = get_config();

    config.show();

    let mut res = BytesMut::new();

    // CommandComplete
    res.put(command_complete("RELOAD"));

    // ReadyForQuery
    res.put_u8(b'Z');
    res.put_i32(5);
    res.put_u8(b'I');

    write_all_half(stream, res).await
}

async fn show_config(stream: &mut OwnedWriteHalf) -> Result<(), Error> {
    let guard = get_config();
    let config = &*guard.clone();
    let config: HashMap<String, String> = config.into();
    drop(guard);

    // Configs that cannot be changed dynamically.
    let immutables = ["host", "port", "connect_timeout"];

    // Columns
    let columns = vec![
        ("key", DataType::Text),
        ("value", DataType::Text),
        ("default", DataType::Text),
        ("changeable", DataType::Text),
    ];

    // Response data
    let mut res = BytesMut::new();
    res.put(row_description(&columns));

    // DataRow rows
    for (key, value) in config {
        let changeable = if immutables.iter().filter(|col| *col == &key).count() == 1 {
            "no".to_string()
        } else {
            "yes".to_string()
        };

        let row = vec![key, value, "-".to_string(), changeable];

        res.put(data_row(&row));
    }

    res.put(command_complete("SHOW"));

    res.put_u8(b'Z');
    res.put_i32(5);
    res.put_u8(b'I');

    write_all_half(stream, res).await
}

/// SHOW STATS
async fn show_stats(stream: &mut OwnedWriteHalf) -> Result<(), Error> {
    let columns = vec![
        ("database", DataType::Text),
        ("total_xact_count", DataType::Numeric),
        ("total_query_count", DataType::Numeric),
        ("total_received", DataType::Numeric),
        ("total_sent", DataType::Numeric),
        ("total_xact_time", DataType::Numeric),
        ("total_query_time", DataType::Numeric),
        ("total_wait_time", DataType::Numeric),
        ("avg_xact_count", DataType::Numeric),
        ("avg_query_count", DataType::Numeric),
        ("avg_recv", DataType::Numeric),
        ("avg_sent", DataType::Numeric),
        ("avg_xact_time", DataType::Numeric),
        ("avg_query_time", DataType::Numeric),
        ("avg_wait_time", DataType::Numeric),
    ];

    let stats = get_stats();
    let mut res = BytesMut::new();
    res.put(row_description(&columns));

    let mut row = vec![
        String::from("all"), // TODO: per-database stats,
    ];

    for column in &columns[1..] {
        row.push(stats.get(column.0).unwrap_or(&0).to_string());
    }

    res.put(data_row(&row));
    res.put(command_complete("SHOW"));

    res.put_u8(b'Z');
    res.put_i32(5);
    res.put_u8(b'I');

    write_all_half(stream, res).await
}