use crate::config::LauncherConfig;
use serde::{Deserialize, Serialize};
use std::io::{Read, Write};
use std::net::{TcpStream, ToSocketAddrs};
use std::time::Duration;

const ACCOUNT_SYNC_PATH: &str = "/openfut/account/sync";
const TIMEOUT: Duration = Duration::from_secs(3);

/// The launcher's view of the account, sent on every sync.
///
/// `persona_id`/`persona_name` are `Option` because omitting them is meaningful:
/// the server then answers with the persona *it* is configured for, which is how
/// first-run account creation learns an identity instead of inventing one.
#[derive(Debug, Serialize)]
#[serde(rename_all = "camelCase")]
struct AccountSyncRequest<'a> {
    #[serde(skip_serializing_if = "Option::is_none")]
    persona_id: Option<u64>,
    #[serde(skip_serializing_if = "Option::is_none")]
    persona_name: Option<&'a str>,
    level: u32,
    experience: u32,
    experience_max: u32,
    account_funds: u32,
    account_funds_cap: u32,
}

#[derive(Debug, Deserialize)]
pub struct AccountSyncResult {
    pub account: AccountSummary,
}

#[derive(Debug, Clone, Deserialize)]
#[serde(rename_all = "camelCase")]
pub struct AccountSummary {
    pub persona_id: u64,
    pub persona_name: String,
    /// Club identity for the account bar. Optional in older envelopes.
    #[serde(default)]
    pub club_name: String,
    #[serde(default)]
    pub club_abbr: String,
    pub level: u32,
    pub experience: u32,
    /// XP required for the next level. Optional; 0 means "unknown".
    #[serde(default)]
    pub experience_max: u32,
    pub account_funds: u32,
    /// EASFC funds ceiling. Optional; 0 means "unknown".
    #[serde(default)]
    pub account_funds_cap: u32,
    pub coins: i64,
    pub unopened_packs: usize,
}

/// Select the persistent EA/FUT account before LSX and FIFA start.
///
/// This deliberately uses a tiny stdlib HTTP client so the launcher does not
/// acquire an async runtime solely for one bounded control-plane request.
pub fn sync(config: &LauncherConfig) -> Result<AccountSummary, String> {
    config.validate_server()?;
    config.validate_account()?;
    let account = post(
        config,
        &AccountSyncRequest {
            persona_id: Some(config.fut_persona_id),
            persona_name: Some(config.fut_persona_name.trim()),
            level: config.fut_account_level,
            experience: config.fut_account_experience,
            experience_max: config.fut_account_experience_max,
            account_funds: config.fut_account_funds,
            account_funds_cap: config.fut_account_funds_cap,
        },
    )?;
    // The server echoes the persona it selected. A different one means the two
    // sides disagree about who is playing, which must never pass silently.
    if account.persona_id != config.fut_persona_id {
        return Err(format!(
            "account server selected persona {} instead of {}",
            account.persona_id, config.fut_persona_id
        ));
    }
    Ok(account)
}

/// Ask the server which account it serves, for first-run account creation.
///
/// Sending no persona makes the server fall back to the one it was started with
/// and answer with its real club and Core coin balance. That is the whole reason
/// the launcher never has to invent a persona id: the identity that matters is
/// the server's, and this is how it is claimed.
pub fn discover(config: &LauncherConfig) -> Result<AccountSummary, String> {
    config.validate_server()?;
    let account = post(
        config,
        &AccountSyncRequest {
            persona_id: None,
            persona_name: None,
            level: config.fut_account_level.max(1),
            experience: config.fut_account_experience,
            experience_max: config.fut_account_experience_max.max(1),
            account_funds: config.fut_account_funds,
            account_funds_cap: config.fut_account_funds_cap,
        },
    )?;
    if account.persona_id == 0 {
        return Err(
            "account server returned no persona — is it configured with \
                    a persona id?"
                .to_string(),
        );
    }
    if account.persona_name.trim().is_empty() {
        return Err("account server returned an empty persona name".to_string());
    }
    Ok(account)
}

/// One bounded POST to `/openfut/account/sync`, returning the account summary.
fn post(config: &LauncherConfig, body: &AccountSyncRequest<'_>) -> Result<AccountSummary, String> {
    let host = config.openfut_server_host.trim();
    let port = config.openfut_account_sync_port;
    let address = (host, port)
        .to_socket_addrs()
        .map_err(|error| format!("cannot resolve account server {host}:{port}: {error}"))?
        .next()
        .ok_or_else(|| format!("account server {host}:{port} resolved to no addresses"))?;
    let mut stream = TcpStream::connect_timeout(&address, TIMEOUT)
        .map_err(|error| format!("cannot connect to account server {host}:{port}: {error}"))?;
    stream
        .set_read_timeout(Some(TIMEOUT))
        .map_err(|error| format!("cannot set account sync timeout: {error}"))?;
    stream
        .set_write_timeout(Some(TIMEOUT))
        .map_err(|error| format!("cannot set account sync timeout: {error}"))?;

    let payload = serde_json::to_vec(body)
        .map_err(|error| format!("cannot encode account sync request: {error}"))?;

    let request = format!(
        "POST {ACCOUNT_SYNC_PATH} HTTP/1.1\r\nHost: {host}:{port}\r\nContent-Type: application/json\r\nContent-Length: {}\r\nConnection: close\r\n\r\n",
        payload.len()
    );
    stream
        .write_all(request.as_bytes())
        .and_then(|()| stream.write_all(&payload))
        .map_err(|error| format!("cannot send account sync request: {error}"))?;

    let mut response = Vec::new();
    stream
        .read_to_end(&mut response)
        .map_err(|error| format!("cannot read account sync response: {error}"))?;
    let separator = response
        .windows(4)
        .position(|window| window == b"\r\n\r\n")
        .ok_or_else(|| "account server returned a malformed HTTP response".to_string())?;
    let headers = std::str::from_utf8(&response[..separator])
        .map_err(|_| "account server returned non-UTF-8 headers".to_string())?;
    let status = headers
        .lines()
        .next()
        .and_then(|line| line.split_whitespace().nth(1))
        .and_then(|value| value.parse::<u16>().ok())
        .ok_or_else(|| "account server returned a malformed status line".to_string())?;
    let response_body = &response[separator + 4..];
    if !(200..300).contains(&status) {
        let detail = String::from_utf8_lossy(response_body);
        return Err(format!(
            "account server rejected sync (HTTP {status}): {detail}"
        ));
    }
    let envelope: AccountSyncResult = serde_json::from_slice(response_body)
        .map_err(|error| format!("account server returned invalid JSON: {error}"))?;
    Ok(envelope.account)
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::net::TcpListener;
    use std::thread;

    #[test]
    fn sync_posts_account_and_reads_selected_profile() {
        let listener = TcpListener::bind("127.0.0.1:0").unwrap();
        let port = listener.local_addr().unwrap().port();
        let server = thread::spawn(move || {
            let (mut socket, _) = listener.accept().unwrap();
            let mut request = Vec::new();
            loop {
                let mut chunk = [0; 1024];
                let count = socket.read(&mut chunk).unwrap();
                assert!(count > 0);
                request.extend_from_slice(&chunk[..count]);
                if let Some(separator) = request.windows(4).position(|w| w == b"\r\n\r\n") {
                    let headers = String::from_utf8_lossy(&request[..separator]);
                    let length = headers
                        .lines()
                        .find_map(|line| line.strip_prefix("Content-Length: "))
                        .unwrap()
                        .parse::<usize>()
                        .unwrap();
                    if request.len() >= separator + 4 + length {
                        break;
                    }
                }
            }
            let request = String::from_utf8_lossy(&request);
            assert!(request.starts_with("POST /openfut/account/sync HTTP/1.1"));
            assert!(request.contains("\"personaId\":12345678"));
            assert!(request.contains("\"personaName\":\"TEST_USER\""));
            let body = r#"{"status":"OK","account":{"personaId":12345678,"personaName":"TEST_USER","level":7,"experience":200,"accountFunds":50,"coins":15000,"unopenedPacks":1}}"#;
            write!(
                socket,
                "HTTP/1.1 200 OK\r\nContent-Type: application/json\r\nContent-Length: {}\r\nConnection: close\r\n\r\n{}",
                body.len(),
                body
            )
            .unwrap();
        });

        let config = LauncherConfig {
            openfut_server_host: "127.0.0.1".into(),
            openfut_account_sync_port: port,
            fut_persona_id: 12345678,
            fut_persona_name: "TEST_USER".into(),
            fut_account_level: 7,
            fut_account_experience: 200,
            ..LauncherConfig::default()
        };
        let selected = sync(&config).unwrap();
        assert_eq!(selected.persona_name, "TEST_USER");
        assert_eq!(selected.coins, 15000);
        assert_eq!(selected.unopened_packs, 1);
        server.join().unwrap();
    }

    /// Serve exactly one `/openfut/account/sync` POST, handing the decoded
    /// request text to `inspect` and replying with `body`.
    fn serve_once(
        inspect: impl FnOnce(&str) + Send + 'static,
        body: &'static str,
    ) -> (u16, thread::JoinHandle<()>) {
        let listener = TcpListener::bind("127.0.0.1:0").unwrap();
        let port = listener.local_addr().unwrap().port();
        let handle = thread::spawn(move || {
            let (mut socket, _) = listener.accept().unwrap();
            let mut request = Vec::new();
            loop {
                let mut chunk = [0; 1024];
                let count = socket.read(&mut chunk).unwrap();
                assert!(count > 0);
                request.extend_from_slice(&chunk[..count]);
                if let Some(separator) = request.windows(4).position(|w| w == b"\r\n\r\n") {
                    let headers = String::from_utf8_lossy(&request[..separator]);
                    let length = headers
                        .lines()
                        .find_map(|line| line.strip_prefix("Content-Length: "))
                        .unwrap()
                        .parse::<usize>()
                        .unwrap();
                    if request.len() >= separator + 4 + length {
                        break;
                    }
                }
            }
            inspect(&String::from_utf8_lossy(&request));
            write!(
                socket,
                "HTTP/1.1 200 OK\r\nContent-Type: application/json\r\nContent-Length: {}\r\nConnection: close\r\n\r\n{}",
                body.len(),
                body
            )
            .unwrap();
        });
        (port, handle)
    }

    #[test]
    fn discover_omits_the_persona_so_the_server_names_its_own() {
        // The point of first-run discovery: the launcher must not send a guessed
        // persona, because the server would echo the guess straight back.
        let (port, server) = serve_once(
            |request| {
                assert!(!request.contains("personaId"), "{request}");
                assert!(!request.contains("personaName"), "{request}");
            },
            r#"{"status":"OK","account":{"personaId":33068179,"personaName":"CAGE","clubName":"OpenFUT","clubAbbr":"OFC","level":1,"experience":0,"accountFunds":0,"coins":29876776,"unopenedPacks":0}}"#,
        );
        let config = LauncherConfig {
            openfut_server_host: "127.0.0.1".into(),
            openfut_account_sync_port: port,
            ..LauncherConfig::default()
        };
        // Deliberately an unconfigured account: discovery must work before one
        // exists, which is the whole reason it does not call `validate_account`.
        assert_eq!(config.fut_persona_id, 0);
        let found = discover(&config).unwrap();
        assert_eq!(found.persona_id, 33_068_179);
        assert_eq!(found.persona_name, "CAGE");
        assert_eq!(found.club_name, "OpenFUT");
        assert_eq!(found.coins, 29_876_776);
        server.join().unwrap();
    }

    #[test]
    fn discover_rejects_a_server_that_names_no_persona() {
        // A zero persona would otherwise be written into the config as a real
        // account and fail much later, at launch, as a mismatch.
        let (port, server) = serve_once(
            |_| {},
            r#"{"status":"OK","account":{"personaId":0,"personaName":"","level":1,"experience":0,"accountFunds":0,"coins":0,"unopenedPacks":0}}"#,
        );
        let config = LauncherConfig {
            openfut_server_host: "127.0.0.1".into(),
            openfut_account_sync_port: port,
            ..LauncherConfig::default()
        };
        let error = discover(&config).unwrap_err();
        assert!(error.contains("no persona"), "{error}");
        server.join().unwrap();
    }

    #[test]
    fn sync_refuses_a_server_that_selects_a_different_persona() {
        let (port, server) = serve_once(
            |_| {},
            r#"{"status":"OK","account":{"personaId":999,"personaName":"OTHER","level":1,"experience":0,"accountFunds":0,"coins":0,"unopenedPacks":0}}"#,
        );
        let config = LauncherConfig {
            openfut_server_host: "127.0.0.1".into(),
            openfut_account_sync_port: port,
            fut_persona_id: 12345678,
            fut_persona_name: "TEST_USER".into(),
            ..LauncherConfig::default()
        };
        let error = sync(&config).unwrap_err();
        assert!(error.contains("999"), "{error}");
        server.join().unwrap();
    }
}