//! RID station mapping: report column number (1..16) -> station metadata.
//! Same precedence as the Python scraper: the runtime file
//! (STATION_CONFIG_PATH, edited through the station CRUD API) if it exists,
//! else the defaults bundled in src/data/stations.json.

use anyhow::{Context, Result};
use serde::Deserialize;
use std::collections::BTreeMap;
use std::path::Path;

const BUNDLED: &str = include_str!("../../../src/data/stations.json");

#[derive(Clone, Debug, Deserialize)]
pub struct StationInfo {
    pub code: String,
    pub thai_name: String,
    pub english_name: String,
    pub latitude: Option<f64>,
    pub longitude: Option<f64>,
    pub geohash: Option<String>,
}

#[derive(Clone, Debug)]
pub struct Stations(BTreeMap<u32, StationInfo>);

impl Stations {
    pub fn load(runtime_path: &Path) -> Result<Self> {
        if runtime_path.exists() {
            let text = std::fs::read_to_string(runtime_path)
                .with_context(|| format!("reading {}", runtime_path.display()))?;
            let stations = Self::parse(&text)
                .with_context(|| format!("parsing {}", runtime_path.display()))?;
            tracing::info!(
                "loaded {} stations from {}",
                stations.0.len(),
                runtime_path.display()
            );
            return Ok(stations);
        }
        let stations = Self::bundled();
        tracing::info!("loaded {} bundled default stations", stations.0.len());
        Ok(stations)
    }

    pub fn bundled() -> Self {
        Self::parse(BUNDLED).expect("bundled stations.json is valid")
    }

    fn parse(text: &str) -> Result<Self> {
        let raw: BTreeMap<String, StationInfo> = serde_json::from_str(text)?;
        let map = raw
            .into_iter()
            .map(|(k, v)| Ok((k.trim().parse::<u32>()?, v)))
            .collect::<Result<BTreeMap<_, _>>>()?;
        Ok(Stations(map))
    }

    /// Metadata for report column `n`, with the Python fallback for unknown
    /// columns (`P.{19+n}` / `Station n`).
    pub fn get(&self, n: u32) -> StationInfo {
        self.0.get(&n).cloned().unwrap_or_else(|| StationInfo {
            code: format!("P.{}", 19 + n),
            thai_name: format!("Station {n}"),
            english_name: format!("Station {n}"),
            latitude: None,
            longitude: None,
            geohash: None,
        })
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn bundled_mapping_has_the_16_rid_gauges() {
        let s = Stations::bundled();
        assert_eq!(s.0.len(), 16);
        assert_eq!(s.get(1).code, "P.20");
        assert_eq!(s.get(8).code, "P.1");
        assert_eq!(s.get(99).code, "P.118"); // Python fallback
    }
}