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

use std::collections::HashMap;

use crate::config::{get_config, parse, Role};
use crate::constants::{OID_INT4, OID_NUMERIC, OID_TEXT};
use crate::errors::Error;
use crate::messages::{custom_protocol_response_ok, error_response, write_all_half};
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("SET ") {
        trace!("SET");
        ignore_set(stream).await
    } else {
        error_response(stream, "Unsupported query against the admin database").await
    }
}

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

    let columns = [
        "name",
        "host",
        "port",
        "database",
        "force_user",
        "pool_size",
        "min_pool_size",
        "reserve_pool",
        "pool_mode",
        "max_connections",
        "current_connections",
        "paused",
        "disabled",
    ];

    let types = [
        OID_TEXT, OID_TEXT, OID_TEXT, OID_TEXT, OID_TEXT, OID_INT4, OID_INT4, OID_INT4, OID_TEXT,
        OID_INT4, OID_INT4, OID_INT4, OID_INT4,
    ];

    let mut res = BytesMut::new();
    let mut row_desc = BytesMut::new();
    row_desc.put_i16(columns.len() as i16);

    for (i, column) in columns.iter().enumerate() {
        row_desc.put_slice(&format!("{}\0", column).as_bytes());

        // Doesn't belong to any table
        row_desc.put_i32(0);

        // Doesn't belong to any table
        row_desc.put_i16(0);

        // Data type
        row_desc.put_i32(types[i]);

        // text size = variable (-1)
        row_desc.put_i16(if types[i] == OID_TEXT { -1 } else { 4 });

        // Type modifier: none that I know
        row_desc.put_i32(-1);

        // Format being used: text (0), binary (1)
        row_desc.put_i16(0);
    }

    res.put_u8(b'T');
    res.put_i32(row_desc.len() as i32 + 4);
    res.put(row_desc);

    for shard in 0..pool.shards() {
        let database_name = &config.shards[&shard.to_string()].database;
        let mut replica_count = 0;
        for server in 0..pool.servers(shard) {
            // DataRow
            let mut data_row = BytesMut::new();
            data_row.put_i16(columns.len() as i16);

            let address = pool.address(shard, server);
            let role = address.role.to_string();
            let name = match role.as_ref() {
                "primary" => format!("shard_{}_primary", shard),
                "replica" => format!("shard_{}_replica_{}", shard, replica_count),
                _ => unreachable!(),
            };
            let connections = pool.connections(shard, server);

            let data = HashMap::from([
                ("host", address.host.to_string()),
                ("port", address.port.to_string()),
                ("role", role),
                ("name", name),
                ("database", database_name.to_string()),
                ("force_user", config.user.name.to_string()),
                ("pool_size", config.general.pool_size.to_string()),
                ("min_pool_size", "0".to_string()),
                ("reserve_pool", "0".to_string()),
                ("pool_mode", config.general.pool_mode.to_string()),
                // There is only one user support at the moment,
                // so max_connections = num of users * pool_size = 1 * pool_size.
                ("max_connections", config.general.pool_size.to_string()),
                ("current_connections", connections.connections.to_string()),
                ("paused", "0".to_string()),
                ("disabled", "0".to_string()),
            ]);

            for column in &columns {
                let value = data[column].as_bytes();

                data_row.put_i32(value.len() as i32);
                data_row.put_slice(&value);
            }

            res.put_u8(b'D');
            res.put_i32(data_row.len() as i32 + 4);
            res.put(data_row);

            if address.role == Role::Replica {
                replica_count += 1;
            }
        }
    }

    let command_complete = BytesMut::from(&"SHOW\0"[..]);
    res.put_u8(b'C');
    res.put_i32(command_complete.len() as i32 + 4);
    res.put(command_complete);

    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
    let command_complete = BytesMut::from(&"RELOAD\0"[..]);
    res.put_u8(b'C');
    res.put_i32(command_complete.len() as i32 + 4);
    res.put(command_complete);

    // 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 = ["key", "value", "default", "changeable"];

    // RowDescription
    let mut row_desc = BytesMut::new();
    row_desc.put_i16(4 as i16); // key, value, default, changeable

    for column in columns {
        row_desc.put_slice(&format!("{}\0", column).as_bytes());

        // Doesn't belong to any table
        row_desc.put_i32(0);

        // Doesn't belong to any table
        row_desc.put_i16(0);

        // Data type
        row_desc.put_i32(OID_TEXT);

        // text size = variable (-1)
        row_desc.put_i16(-1);

        // Type modifier: none that I know
        row_desc.put_i32(-1);

        // Format being used: text (0), binary (1)
        row_desc.put_i16(0);
    }

    // Response data
    let mut res = BytesMut::new();
    res.put_u8(b'T');
    res.put_i32(row_desc.len() as i32 + 4);
    res.put(row_desc);

    // DataRow rows
    for (key, value) in config {
        let mut data_row = BytesMut::new();

        data_row.put_i16(4 as i16); // key, value, default, changeable

        let key_bytes = key.as_bytes();
        let value = value.as_bytes();

        data_row.put_i32(key_bytes.len() as i32);
        data_row.put_slice(&key_bytes);

        data_row.put_i32(value.len() as i32);
        data_row.put_slice(&value);

        data_row.put_i32(1 as i32);
        data_row.put_slice(&"-".as_bytes());

        let changeable = if immutables.iter().filter(|col| *col == &key).count() == 1 {
            "no".as_bytes()
        } else {
            "yes".as_bytes()
        };
        data_row.put_i32(changeable.len() as i32);
        data_row.put_slice(&changeable);

        res.put_u8(b'D');
        res.put_i32(data_row.len() as i32 + 4);
        res.put(data_row);
    }

    res.put_u8(b'C');
    res.put_i32("SHOW CONFIG\0".as_bytes().len() as i32 + 4);
    res.put_slice(&"SHOW CONFIG\0".as_bytes());

    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 = [
        "database",
        "total_xact_count",
        "total_query_count",
        "total_received",
        "total_sent",
        "total_xact_time",
        "total_query_time",
        "total_wait_time",
        "avg_xact_count",
        "avg_query_count",
        "avg_recv",
        "avg_sent",
        "avg_xact_time",
        "avg_query_time",
        "avg_wait_time",
    ];

    let stats = get_stats();
    let mut res = BytesMut::new();
    let mut row_desc = BytesMut::new();
    let mut data_row = BytesMut::new();

    // Number of columns: 1
    row_desc.put_i16(columns.len() as i16);
    data_row.put_i16(columns.len() as i16);

    for (i, column) in columns.iter().enumerate() {
        // RowDescription

        // Column name
        row_desc.put_slice(&format!("{}\0", column).as_bytes());

        // Doesn't belong to any table
        row_desc.put_i32(0);

        // Doesn't belong to any table
        row_desc.put_i16(0);

        // Data type
        row_desc.put_i32(if i == 0 { OID_TEXT } else { OID_NUMERIC });

        // Numeric/text size = variable (-1)
        row_desc.put_i16(-1);

        // Type modifier: none that I know
        row_desc.put_i32(-1);

        // Format being used: text (0), binary (1)
        row_desc.put_i16(0);

        // DataRow
        let value = if i == 0 {
            String::from("all shards")
        } else {
            stats.get(&column.to_string()).unwrap_or(&0).to_string()
        };

        data_row.put_i32(value.len() as i32);
        data_row.put_slice(value.as_bytes());
    }

    let command_complete = BytesMut::from(&"SHOW\0"[..]);

    res.put_u8(b'T');
    res.put_i32(row_desc.len() as i32 + 4);
    res.put(row_desc);

    res.put_u8(b'D');
    res.put_i32(data_row.len() as i32 + 4);
    res.put(data_row);

    res.put_u8(b'C');
    res.put_i32(command_complete.len() as i32 + 4);
    res.put(command_complete);

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

    write_all_half(stream, res).await
}