/// Gum Catalogue of Southern HII Regions (Gum 1955).
/// Fetched from VizieR XI/75. Mostly Dec < -30° but ~20-30 entries are in range.
use anyhow::Context;
use chrono::Utc;

use crate::catalog::filter::{CatalogEntry, guide_star_density_from_coords};
use crate::catalog::fetch::{format_ra_hms, format_dec_dms};
use crate::catalog::popular_names::popular_names;
use crate::config::{FOV_ARCMIN_H, FOV_ARCMIN_W};

const VIZIER_GUM_URL: &str =
    "https://vizier.cds.unistra.fr/viz-bin/asu-tsv\
?-source=XI/75\
&-out=Gum\
&-out=_RA\
&-out=_DE\
&-out=Diam\
&-out.max=200\
&-oc.form=dec";

#[derive(Debug, Clone)]
struct GumRow {
    id: u32,
    ra_deg: f64,
    dec_deg: f64,
    diam_arcmin: f64,
}

pub async fn fetch_gum() -> anyhow::Result<Vec<CatalogEntry>> {
    match fetch_from_vizier().await {
        Ok(entries) if !entries.is_empty() => {
            tracing::info!("Gum: loaded {} entries from VizieR XI/75", entries.len());
            Ok(entries)
        }
        Ok(_) => {
            tracing::warn!("Gum: VizieR returned 0 rows — using hardcoded fallback");
            Ok(build_entries_from_rows(get_prominent_gum()))
        }
        Err(e) => {
            tracing::warn!("Gum fetch from VizieR failed ({}) — using hardcoded fallback", e);
            Ok(build_entries_from_rows(get_prominent_gum()))
        }
    }
}

async fn fetch_from_vizier() -> anyhow::Result<Vec<CatalogEntry>> {
    let client = reqwest::Client::builder()
        .timeout(std::time::Duration::from_secs(60))
        .user_agent("astronome/1.0")
        .build()?;

    let text = client
        .get(VIZIER_GUM_URL)
        .send()
        .await
        .context("Gum fetch request failed")?
        .text()
        .await
        .context("Gum response read failed")?;

    let rows = parse_vizier_tsv(&text);
    tracing::info!("Gum: parsed {} rows from VizieR XI/75", rows.len());

    if rows.is_empty() {
        anyhow::bail!("no rows parsed from VizieR Gum response");
    }

    let filtered: Vec<GumRow> = rows
        .into_iter()
        .filter(|r| r.dec_deg >= -30.0 && r.dec_deg <= 75.0 && r.diam_arcmin >= 2.0)
        .collect();

    tracing::info!("Gum: {} rows pass filters (Dec >= -30°)", filtered.len());
    Ok(build_entries_from_rows(filtered))
}

fn parse_vizier_tsv(text: &str) -> Vec<GumRow> {
    let mut rows = Vec::new();
    let mut header: Vec<String> = Vec::new();
    let mut past_separator = false;

    for line in text.lines() {
        if line.starts_with('#') {
            continue;
        }
        let trimmed = line.trim();
        if trimmed.is_empty() {
            continue;
        }
        if header.is_empty() {
            header = trimmed.split('\t').map(|s| s.trim().to_string()).collect();
            if header.len() < 2 {
                header = trimmed.split_whitespace().map(|s| s.to_string()).collect();
            }
            continue;
        }
        if !past_separator {
            if trimmed.starts_with("---") || trimmed.chars().all(|c| c == '-' || c == '\t' || c == ' ') {
                past_separator = true;
            }
            continue;
        }

        let cols: Vec<&str> = if line.contains('\t') {
            line.split('\t').map(|s| s.trim()).collect()
        } else {
            line.split_whitespace().collect()
        };

        if cols.len() < 3 {
            continue;
        }

        let col_idx = |name: &str| -> Option<usize> {
            header.iter().position(|h| h.eq_ignore_ascii_case(name))
        };

        let id = col_idx("Gum")
            .and_then(|i| cols.get(i))
            .and_then(|s| s.parse::<u32>().ok());

        let ra = col_idx("_RA")
            .and_then(|i| cols.get(i))
            .and_then(|s| s.parse::<f64>().ok());

        let dec = col_idx("_DE")
            .and_then(|i| cols.get(i))
            .and_then(|s| s.parse::<f64>().ok());

        let diam = col_idx("Diam")
            .and_then(|i| cols.get(i))
            .and_then(|s| s.parse::<f64>().ok())
            .unwrap_or(15.0);

        if let (Some(id), Some(ra), Some(dec)) = (id, ra, dec) {
            rows.push(GumRow { id, ra_deg: ra, dec_deg: dec, diam_arcmin: diam });
        }
    }
    rows
}

fn build_entries_from_rows(rows: Vec<GumRow>) -> Vec<CatalogEntry> {
    let now = Utc::now().timestamp();
    let names = popular_names();
    rows.into_iter()
        .filter(|r| r.dec_deg >= -30.0 && r.dec_deg <= 75.0 && r.diam_arcmin >= 2.0)
        .map(|r| build_entry(r, now, &names))
        .collect()
}

fn build_entry(
    r: GumRow,
    now: i64,
    names: &std::collections::HashMap<&'static str, &'static str>,
) -> CatalogEntry {
    let id = format!("Gum{}", r.id);
    let fov_fill = (r.diam_arcmin / FOV_ARCMIN_H).min(1.0) * 100.0;
    let panels_w = ((r.diam_arcmin / FOV_ARCMIN_W).ceil() as i32).max(1);
    let panels_h = ((r.diam_arcmin / FOV_ARCMIN_H).ceil() as i32).max(1);
    let mosaic = panels_w > 1 || panels_h > 1;
    let density = guide_star_density_from_coords(r.ra_deg, r.dec_deg);
    let common_name = names.get(id.as_str()).map(|s| s.to_string());
    let is_highlight = common_name.is_some();

    CatalogEntry {
        id: id.clone(),
        name: id,
        common_name,
        obj_type: "emission_nebula".to_string(),
        ra_deg: r.ra_deg,
        dec_deg: r.dec_deg,
        ra_h: format_ra_hms(r.ra_deg),
        dec_dms: format_dec_dms(r.dec_deg),
        constellation: None,
        size_arcmin_maj: Some(r.diam_arcmin),
        size_arcmin_min: Some(r.diam_arcmin * 0.7),
        pos_angle_deg: None,
        mag_v: None,
        surface_brightness: None,
        hubble_type: None,
        messier_num: None,
        is_highlight,
        fov_fill_pct: Some(fov_fill),
        mosaic_flag: mosaic,
        mosaic_panels_w: panels_w,
        mosaic_panels_h: panels_h,
        difficulty: Some(3),
        guide_star_density: Some(density.to_string()),
        fetched_at: now,
    }
}

fn get_prominent_gum() -> Vec<GumRow> {
    // Small fallback — most Gum objects are far south, these are in range
    vec![
        GumRow { id: 12, ra_deg: 126.0, dec_deg: -47.5, diam_arcmin: 36.0 },
        GumRow { id: 17, ra_deg: 131.0, dec_deg: -43.0, diam_arcmin: 20.0 },
    ]
}