// SPDX-FileCopyrightText: 2025 Tomasz Kramkowski <tomasz@kramkow.ski>
// SPDX-License-Identifier: GPL-3.0-or-later

use std::{
    collections::HashMap, fmt, fs::File, io::Read, os::unix::fs::PermissionsExt, path::Path,
    process, time::Duration,
};

use anyhow::bail;
use rumqttc::{AsyncClient, EventLoop, MqttOptions, QoS};
use serde::{
    de::{self, Visitor},
    Deserialize, Deserializer,
};

use crate::PROGRAM;

#[derive(Deserialize, Debug)]
pub struct Credentials {
    pub username: String,
    pub password: String,
}

fn default_host() -> String {
    "localhost".to_string()
}

fn default_port() -> u16 {
    1883
}

fn default_qos() -> QoS {
    QoS::ExactlyOnce
}

fn default_id() -> String {
    PROGRAM.to_string()
}

fn default_timeout() -> Duration {
    Duration::from_secs(60)
}

#[allow(clippy::enum_variant_names)]
#[derive(Deserialize, Debug)]
#[serde(remote = "QoS", rename_all = "kebab-case")]
#[repr(u8)]
pub enum QoSDef {
    AtMostOnce = 0,
    AtLeastOnce = 1,
    ExactlyOnce = 2,
}

pub fn deserialize_qos_opt<'de, D>(deserializer: D) -> Result<Option<QoS>, D::Error>
where
    D: Deserializer<'de>,
{
    #[derive(Deserialize)]
    struct Helper(#[serde(with = "QoSDef")] QoS);

    let helper = Option::deserialize(deserializer)?;
    Ok(helper.map(|Helper(external)| external))
}

#[derive(Debug, PartialEq, Clone)]
pub struct Program {
    // TODO: Figure out a way to allow arbitrary unix paths (arbitrary
    // non-unicode) without base64
    pub command: Box<[String]>,
    pub timeout: Option<Duration>,
}

impl<'de> Deserialize<'de> for Program {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: Deserializer<'de>,
    {
        struct VecOrProgram;

        impl<'de> Visitor<'de> for VecOrProgram {
            type Value = Program;

            fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
                formatter.write_str("map or seq")
            }

            fn visit_seq<A>(self, seq: A) -> Result<Self::Value, A::Error>
            where
                A: serde::de::SeqAccess<'de>,
            {
                let vec: Box<[String]> =
                    Deserialize::deserialize(de::value::SeqAccessDeserializer::new(seq))?;
                Ok(Program {
                    command: vec,
                    timeout: None,
                })
            }

            fn visit_map<A>(self, map: A) -> Result<Self::Value, A::Error>
            where
                A: serde::de::MapAccess<'de>,
            {
                #[derive(Deserialize)]
                struct Helper {
                    command: Box<[String]>,
                    #[serde(default, deserialize_with = "deserialize_timeout_opt")]
                    timeout: Option<Duration>,
                }

                let helper: Helper =
                    Deserialize::deserialize(de::value::MapAccessDeserializer::new(map))?;
                Ok(Program {
                    command: helper.command,
                    timeout: helper.timeout,
                })
            }
        }

        deserializer.deserialize_any(VecOrProgram)
    }
}

#[derive(Debug)]
pub struct Route {
    pub programs: Box<[Program]>,
    pub qos: Option<QoS>,
}

impl<'de> Deserialize<'de> for Route {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: Deserializer<'de>,
    {
        struct VecOrRoute;

        impl<'de> Visitor<'de> for VecOrRoute {
            type Value = Route;

            fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
                formatter.write_str("map or seq")
            }

            fn visit_seq<A>(self, seq: A) -> Result<Self::Value, A::Error>
            where
                A: serde::de::SeqAccess<'de>,
            {
                let vec: Box<[Program]> =
                    Deserialize::deserialize(de::value::SeqAccessDeserializer::new(seq))?;
                Ok(Route {
                    programs: vec,
                    qos: None,
                })
            }

            fn visit_map<A>(self, map: A) -> Result<Self::Value, A::Error>
            where
                A: serde::de::MapAccess<'de>,
            {
                #[derive(Deserialize)]
                struct Helper {
                    programs: Box<[Program]>,
                    #[serde(default, deserialize_with = "deserialize_qos_opt")]
                    qos: Option<QoS>,
                }

                let helper: Helper =
                    Deserialize::deserialize(de::value::MapAccessDeserializer::new(map))?;
                Ok(Route {
                    programs: helper.programs,
                    qos: helper.qos,
                })
            }
        }

        deserializer.deserialize_any(VecOrRoute)
    }
}

pub fn deserialize_timeout<'de, D>(deserializer: D) -> Result<Duration, D::Error>
where
    D: Deserializer<'de>,
{
    struct DurationVisitor;

    impl<'de> de::Visitor<'de> for DurationVisitor {
        type Value = Duration;

        fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
            formatter.write_str("a positive number")
        }

        fn visit_i64<E>(self, v: i64) -> Result<Self::Value, E>
        where
            E: de::Error,
        {
            if v < 0 {
                return Err(de::Error::invalid_value(
                    de::Unexpected::Signed(v),
                    &"a non-negative number",
                ));
            }
            if v == 0 {
                Ok(Duration::MAX)
            } else {
                Ok(Duration::from_secs(v as u64))
            }
        }

        fn visit_f64<E>(self, v: f64) -> Result<Self::Value, E>
        where
            E: de::Error,
        {
            if v < 0.0 {
                return Err(de::Error::invalid_value(
                    de::Unexpected::Float(v),
                    &"a non-negative number",
                ));
            }
            if v == 0.0 {
                Ok(Duration::MAX)
            } else {
                Ok(Duration::from_secs_f64(v))
            }
        }
    }

    deserializer.deserialize_any(DurationVisitor)
}

pub fn deserialize_timeout_opt<'de, D>(deserializer: D) -> Result<Option<Duration>, D::Error>
where
    D: Deserializer<'de>,
{
    #[derive(Deserialize)]
    struct Helper(#[serde(deserialize_with = "deserialize_timeout")] Duration);

    let helper = Option::deserialize(deserializer)?;
    Ok(helper.map(|Helper(external)| external))
}

#[derive(Deserialize, Debug)]
pub struct Config {
    #[serde(default = "default_host")]
    pub host: String,
    #[serde(default = "default_port")]
    pub port: u16,
    #[serde(with = "QoSDef", default = "default_qos")]
    pub qos: QoS,
    #[serde(default = "default_timeout", deserialize_with = "deserialize_timeout")]
    pub timeout: Duration,
    pub credentials: Option<Credentials>,
    #[serde(default = "default_id")]
    pub id: String,
    pub routes: HashMap<String, Route>,
}

impl Config {
    pub fn mqtt_client(&self) -> (AsyncClient, EventLoop) {
        let client_id = format!("{}_{}", self.id, process::id());
        let mut options = MqttOptions::new(client_id, &self.host, self.port);
        if let Some(credentials) = &self.credentials {
            options.set_credentials(&credentials.username, &credentials.password);
        }
        // TODO: Make configurable
        options.set_keep_alive(Duration::from_secs(5));
        options.set_max_packet_size(10 * 1024 * 1024, 10 * 1024 * 1024);
        AsyncClient::new(options, 10)
    }
}

pub fn load<P: AsRef<Path>>(path: P) -> anyhow::Result<Config> {
    let mut f = File::open(path)?;
    let mut config = String::new();
    f.read_to_string(&mut config)?;
    let config: Config = toml::from_str(&config)?;
    if config.credentials.is_some() {
        let mode = f.metadata()?.permissions().mode();
        if mode & 0o044 != 0o000 {
            bail!("Config file contains credentials while being group or world readable.");
        }
    }
    Ok(config)
}

#[cfg(test)]
mod tests {
    use super::*;
    use rumqttc::QoS;
    use std::time::Duration;

    impl Program {
        fn new(command: Vec<&str>) -> Self {
            Program {
                command: command.into_iter().map(str::to_string).collect(),
                timeout: None,
            }
        }

        fn new_with_timeout(command: Vec<&str>, timeout: Duration) -> Self {
            Program {
                command: command.into_iter().map(str::to_string).collect(),
                timeout: Some(timeout),
            }
        }
    }

    #[test]
    fn load_full_config() {
        let toml_str = r#"
            host = "foo.bar.baz"
            port = 1234
            qos = "at-most-once"
            id = "custom-id"
            timeout = 15.5

            [credentials]
            username = "testuser"
            password = "testpassword"

            [routes]
            "topic/map" = { programs = [
                    ["/bin/program1"],
                    ["/bin/program2", "arg"],
                    { command = ["/bin/program3", "arg"]},
                ], qos = "exactly-once" }
            "topic/seq" = [
                ["/bin/program4", "arg"],
                { command = ["/bin/program5"], timeout = 1.2 },
            ]
        "#;

        let config: Config = toml::from_str(toml_str).expect("Failed to parse full config");

        assert_eq!(config.host, "foo.bar.baz");
        assert_eq!(config.port, 1234);
        assert_eq!(config.qos, QoS::AtMostOnce);
        assert_eq!(config.id, "custom-id");
        assert_eq!(config.timeout, Duration::from_secs_f64(15.5));

        let creds = config.credentials.expect("Credentials should be present");
        assert_eq!(creds.username, "testuser");
        assert_eq!(creds.password, "testpassword");

        assert_eq!(config.routes.len(), 2);

        let route_map = config.routes.get("topic/map").unwrap();
        assert_eq!(
            route_map.programs,
            vec![
                Program::new(vec!["/bin/program1"]),
                Program::new(vec!["/bin/program2", "arg"]),
                Program::new(vec!["/bin/program3", "arg"]),
            ]
        );
        assert_eq!(route_map.qos, Some(QoS::ExactlyOnce));

        let route_seq = config.routes.get("topic/seq").unwrap();
        assert_eq!(
            route_seq.programs,
            vec![
                Program::new(vec!["/bin/program4", "arg"]),
                Program::new_with_timeout(vec!["/bin/program5"], Duration::from_secs_f64(1.2)),
            ]
        );
        assert_eq!(route_seq.qos, None);
    }

    #[test]
    fn load_minimal_config() {
        let config: Config = toml::from_str("[routes]").expect("Failed to parse minimal config");

        assert_eq!(config.host, default_host());
        assert_eq!(config.port, default_port());
        assert_eq!(config.qos, default_qos());
        assert_eq!(config.id, default_id());
        assert_eq!(config.timeout, default_timeout());
        assert!(config.credentials.is_none());
        assert!(config.routes.is_empty());
    }

    #[test]
    fn load_route_seq() {
        let toml_str = r#"
            [routes]
            "some/topic" = [["/foo/bar"], ["/baz/qux", "arg"]]
        "#;

        let config: Config = toml::from_str(toml_str).unwrap();
        let route = config.routes.get("some/topic").unwrap();

        assert_eq!(
            route.programs,
            vec![
                Program::new(vec!["/foo/bar"]),
                Program::new(vec!["/baz/qux", "arg"])
            ]
        );
        assert_eq!(route.qos, None);
    }

    #[test]
    fn load_route_map() {
        let toml_str = r#"
            [routes]
            "topic/with_qos" = { programs = [["/foo/bar", "arg"]], qos = "at-least-once" }
            "topic/without_qos" = { programs = [["/baz/qux"]] }
        "#;

        let config: Config = toml::from_str(toml_str).unwrap();

        let route_with_qos = config.routes.get("topic/with_qos").unwrap();
        assert_eq!(
            route_with_qos.programs,
            vec![Program::new(vec!["/foo/bar", "arg"])]
        );
        assert_eq!(route_with_qos.qos, Some(QoS::AtLeastOnce));

        let route_without_qos = config.routes.get("topic/without_qos").unwrap();
        assert_eq!(
            route_without_qos.programs,
            vec![Program::new(vec!["/baz/qux"])]
        );
        assert_eq!(route_without_qos.qos, None);
    }

    #[test]
    fn load_timeout() {
        let config_int: Config = toml::from_str("timeout = 10\n[routes]").unwrap();
        assert_eq!(config_int.timeout, Duration::from_secs(10));

        let config_float: Config = toml::from_str("timeout = 2.5\n[routes]").unwrap();
        assert_eq!(config_float.timeout, Duration::from_secs_f64(2.5));

        let config_zero: Config = toml::from_str("timeout = 0\n[routes]").unwrap();
        assert_eq!(config_zero.timeout, Duration::MAX);

        let config_zero: Config = toml::from_str("timeout = 0.0\n[routes]").unwrap();
        assert_eq!(config_zero.timeout, Duration::MAX);
    }

    #[test]
    fn load_timeout_negative() {
        let result = toml::from_str::<Config>("timeout = -10\n[routes]");
        assert!(result.is_err());

        let result = toml::from_str::<Config>("timeout = -1.0\n[routes]");
        assert!(result.is_err());
    }

    #[test]
    fn load_qos() {
        let toml_str = r#"
            [routes]
            "at-most-once" = { programs = [], qos = "at-most-once" }
            "at-least-once" = { programs = [], qos = "at-least-once" }
            "exactly-once" = { programs = [], qos = "exactly-once" }
        "#;
        let config: Config = toml::from_str(toml_str).unwrap();
        assert_eq!(
            config.routes.get("at-most-once").unwrap().qos.unwrap(),
            QoS::AtMostOnce
        );
        assert_eq!(
            config.routes.get("at-least-once").unwrap().qos.unwrap(),
            QoS::AtLeastOnce
        );
        assert_eq!(
            config.routes.get("exactly-once").unwrap().qos.unwrap(),
            QoS::ExactlyOnce
        );
    }
}