use std::fmt::{Debug, Display};

use anyhow::{Context, Result};
use chrono::{DateTime, Local, TimeZone, Utc};
use serde::{de, Deserialize, Deserializer};

#[derive(Deserialize, Debug)]
#[serde(rename_all = "PascalCase")]
pub struct Departure {
    line_name: String,
    direction: String,
    #[serde(default, deserialize_with = "deserialize_realtime")]
    real_time: Option<DateTime<Local>>,
    #[serde(deserialize_with = "deserialize_timestamp")]
    scheduled_time: DateTime<Local>,
}

#[derive(Deserialize, Debug)]
#[serde(rename_all = "PascalCase")]
pub struct Response {
    pub departures: Vec<Departure>,
}

/// Deserialize a timestamp in the form of '/Date(1671713820000-0000)/'
fn deserialize_timestamp<'de, D>(deserializer: D) -> Result<DateTime<Local>, D::Error>
where
    D: Deserializer<'de>,
{
    let s = String::deserialize(deserializer)?;
    let timestamp: i64 = s
        .trim_start_matches("/Date(")
        .trim_end_matches(")/")
        .split('-')
        .next()
        .ok_or_else(|| de::Error::custom("Invalid timestamp format"))?
        .parse()
        .map_err(de::Error::custom)?;
    let result = Utc.timestamp_millis_opt(timestamp).unwrap();

    let local_tz = chrono::offset::Local::now().timezone();
    Ok(result.with_timezone(&local_tz))
}

fn deserialize_realtime<'de, D>(deserializer: D) -> Result<Option<DateTime<Local>>, D::Error>
where
    D: Deserializer<'de>,
{
    match deserialize_timestamp(deserializer) {
        Ok(inner) => Ok(Some(inner)),
        Err(_) => Ok(None),
    }
}

impl Display for Departure {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(&format!("{} {}\n", &self.line_name, &self.direction))?;

        let scheduled_time = self.scheduled_time.format("%H:%M");
        f.write_str(&format!("departure: {}", &scheduled_time))?;

        if let Some(real_time) = self.real_time {
            let actual_time = real_time.format("%H:%M");
            if real_time != self.scheduled_time {
                f.write_str(&format!(" | delayed: {actual_time} "))?;
            }
        }
        Ok(())
    }
}

pub fn format_departures(response: Response) -> String {
    let departures: Vec<String> = response.departures.iter().map(|d| d.to_string()).collect();
    departures.join("\n\n")
}

#[derive(Deserialize, Debug)]
#[serde(rename_all = "PascalCase")]
pub struct PointFinderResponse {
    #[serde(deserialize_with = "deserialize_points", rename = "Points")]
    pub point: Point,
}

#[derive(Deserialize, Debug)]
#[serde(rename_all = "PascalCase")]
pub struct Point {
    pub stopid: String,
    pub name: String,
    pub area: String,
}

impl From<(&str, &str, &str)> for Point {
    fn from(value: (&str, &str, &str)) -> Self {
        Self {
            stopid: value.0.into(),
            name: value.1.into(),
            area: value.2.into(),
        }
    }
}

/// Deserialize a Point Response in the form of
/// '\"33000742|||Helmholtzstraße|5655904|4621157|0||\"'
fn extract_data_from_response(line: &str) -> Result<Point> {
    let mut iter = line.trim_start_matches("\\\"").split_terminator('|');

    let stopid = iter.next().context("getting stopid from line")?;
    let area = iter.nth(1).context("getting area from line")?;
    let name = iter.next().context("getting stop name from line")?;
    Ok((stopid, name, area).into())
}

fn deserialize_points<'de, D>(deserializer: D) -> Result<Point, D::Error>
where
    D: Deserializer<'de>,
{
    let stops: Vec<String> = Vec::deserialize(deserializer)?;
    let first_stop_line = stops
        .first()
        .ok_or_else(|| de::Error::custom("could not get first stop"))?;
    let point = extract_data_from_response(first_stop_line).map_err(de::Error::custom)?;
    Ok(point)
}