use std::{fmt::Display, sync::LazyLock, time::Duration};

use axum::http::status::StatusCode;
use serde::{Deserialize, Serialize};
use url::Url;

use crate::status::Sender;

use super::IntoService;

static CLIENT: LazyLock<reqwest::Client> = LazyLock::new(reqwest::Client::new);

#[derive(Debug, thiserror::Error)]
pub enum Error {
    #[error("Request error: {0}")]
    Reqwest(#[from] reqwest::Error),
    #[error("Bad status code: {0}")]
    StatusCode(u16),
}

#[derive(Debug, Clone, Deserialize, Serialize)]
pub struct Http {
    pub url: Url,
    #[serde(default)]
    pub method: Method,
    #[serde(default, with = "status_code")]
    pub status_code: StatusCode,
    #[serde(default = "super::default_interval")]
    pub interval: Duration,
}

impl Http {
    async fn check(&self) -> Result<(), Error> {
        let client = CLIENT.clone();
        let req = client
            .request(self.method.into(), self.url.clone())
            .build()?;
        let status_code = client.execute(req).await?.status().as_u16();
        (status_code == self.status_code)
            .then_some(())
            .ok_or_else(|| Error::StatusCode(status_code))
    }
}

impl IntoService for Http {
    async fn into_service(self, tx: Sender) {
        let mut interval = tokio::time::interval(self.interval);
        loop {
            interval.tick().await;
            let res = self.check().await;
            tx.send_if_modified(|s| s.update(res.into()));
        }
    }
}

#[derive(Debug, Clone, Copy, Default, Deserialize, Serialize)]
pub enum Method {
    #[serde(alias = "get", alias = "GET")]
    #[default]
    Get,
    #[serde(alias = "post", alias = "POST")]
    Post,
}

impl From<Method> for reqwest::Method {
    fn from(value: Method) -> Self {
        match value {
            Method::Get => reqwest::Method::GET,
            Method::Post => reqwest::Method::POST,
        }
    }
}

impl Display for Method {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Method::Get => write!(f, "GET"),
            Method::Post => write!(f, "POST"),
        }
    }
}

pub mod status_code {
    use axum::http::StatusCode;
    use serde::{
        de::{self, Unexpected, Visitor},
        Deserializer, Serializer,
    };
    use std::fmt;

    /// Implementation detail. Use derive annotations instead.
    #[inline]
    pub fn serialize<S: Serializer>(status: &StatusCode, ser: S) -> Result<S::Ok, S::Error> {
        ser.serialize_u16(status.as_u16())
    }

    pub(crate) struct StatusVisitor;

    impl StatusVisitor {
        #[inline(never)]
        fn make<E: de::Error>(&self, val: u64) -> Result<StatusCode, E> {
            if (100..1000).contains(&val) {
                if let Ok(s) = StatusCode::from_u16(val as u16) {
                    return Ok(s);
                }
            }
            Err(de::Error::invalid_value(Unexpected::Unsigned(val), self))
        }
    }

    impl<'de> Visitor<'de> for StatusVisitor {
        type Value = StatusCode;

        #[inline]
        fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
            formatter.write_str("status code")
        }

        #[inline]
        fn visit_some<D: Deserializer<'de>>(
            self,
            deserializer: D,
        ) -> Result<Self::Value, D::Error> {
            deserializer.deserialize_u16(self)
        }

        #[inline]
        fn visit_i64<E: de::Error>(self, val: i64) -> Result<Self::Value, E> {
            self.make(val as _)
        }

        #[inline]
        fn visit_u64<E: de::Error>(self, val: u64) -> Result<Self::Value, E> {
            self.make(val)
        }
    }

    /// Implementation detail.
    #[inline]
    pub fn deserialize<'de, D>(de: D) -> Result<StatusCode, D::Error>
    where
        D: Deserializer<'de>,
    {
        de.deserialize_u16(StatusVisitor)
    }
}