//! Eurocontrol RAD (Route Availability Document) parsing.
//!
//! The RAD is a public per-AIRAC Excel workbook (see the `rad-data-source`
//! reference). This crate reads it with `calamine` and turns the annexes into a
//! restriction model the routing/validation engine can apply.

use anyhow::Result;
use calamine::{open_workbook, Data, Reader, Xlsx};

// The RAD data model lives in `core` (so routing/validation can use it without
// pulling in `calamine`); this crate produces those types.
pub use flightplanner_core::rad::{Area, DctKind, DctRestriction, FraEdge, FraPoint, LevelCap, RadData};

/// Parse the official EUROCONTROL "FRA Points" list (a separate `.xlsx` — see the
/// `fra-points-official` note). Sheet `"FRA Points"`, one row per point.
pub fn parse_fra_points(path: &str) -> Result<Vec<FraPoint>> {
    let rows = rows(path, "FRA Points")?;
    Ok(rows
        .iter()
        .skip(1) // header
        .filter_map(|r| {
            let name = cell(r, 2);
            let lat = parse_lat(&cell(r, 3));
            let lon = parse_lon(&cell(r, 4));
            let (name, lat, lon) = match (name.is_empty(), lat, lon) {
                (false, Some(la), Some(lo)) => (name, la, lo),
                _ => return None,
            };
            let (level_lo, level_hi) = parse_levels(&cell(r, 11));
            Some(FraPoint {
                name,
                lat,
                lon,
                areas: split_amp(&cell(r, 5)),
                enroute: cell(r, 6).trim_matches('-').trim().to_string(),
                arrdep: cell(r, 7).trim_matches('-').trim().to_string(),
                arr_airports: split_ws(&cell(r, 8)),
                dep_airports: split_ws(&cell(r, 9)),
                flos: cell(r, 10).trim_matches('-').trim().to_string(),
                level_lo,
                level_hi,
                loc_ind: split_ws(&cell(r, 13)),
            })
        })
        .collect())
}

/// Latitude `XDDMMSS` (X = N/S) → signed decimal degrees.
fn parse_lat(s: &str) -> Option<f64> {
    let s = s.trim();
    let b = s.as_bytes();
    if b.len() < 7 {
        return None;
    }
    let sign = match b[0] {
        b'N' => 1.0,
        b'S' => -1.0,
        _ => return None,
    };
    let d: f64 = s[1..3].parse().ok()?;
    let m: f64 = s[3..5].parse().ok()?;
    let sec: f64 = s[5..7].parse().ok()?;
    Some(sign * (d + m / 60.0 + sec / 3600.0))
}

/// Longitude `XDDDMMSS` (X = E/W) → signed decimal degrees.
fn parse_lon(s: &str) -> Option<f64> {
    let s = s.trim();
    let b = s.as_bytes();
    if b.len() < 8 {
        return None;
    }
    let sign = match b[0] {
        b'E' => 1.0,
        b'W' => -1.0,
        _ => return None,
    };
    let d: f64 = s[1..4].parse().ok()?;
    let m: f64 = s[4..6].parse().ok()?;
    let sec: f64 = s[6..8].parse().ok()?;
    Some(sign * (d + m / 60.0 + sec / 3600.0))
}

/// "FL195 / FL660" → (Some(195), Some(660)); "GND / FL245" → (Some(0), Some(245)).
fn parse_levels(s: &str) -> (Option<i32>, Option<i32>) {
    let up = s.to_uppercase();
    let mut fls: Vec<i32> = Vec::new();
    let mut rest = up.as_str();
    while let Some(p) = rest.find("FL") {
        rest = &rest[p + 2..];
        let num: String = rest.chars().take_while(char::is_ascii_digit).collect();
        rest = &rest[num.len()..];
        if let Ok(n) = num.parse::<i32>() {
            fls.push(n);
        }
    }
    let lo = fls.first().copied().or_else(|| up.contains("GND").then_some(0));
    let hi = fls.get(1).copied().or_else(|| if fls.len() == 1 { None } else { fls.first().copied() });
    (lo, hi)
}

fn split_amp(s: &str) -> Vec<String> {
    s.split('&').map(|x| x.trim().to_string()).filter(|x| !x.is_empty()).collect()
}

fn split_ws(s: &str) -> Vec<String> {
    s.split([' ', ',', '\n']).map(|x| x.trim().to_string()).filter(|x| !x.is_empty()).collect()
}

/// Parse the annexes we currently model from the workbook at `path`.
pub fn parse(path: &str) -> Result<RadData> {
    Ok(RadData {
        areas: parse_areas(path)?,
        dct: parse_dct(path)?,
        fra_edges: parse_fra_edges(path)?,
        level_caps: parse_level_caps(path)?,
        fra_points: Vec::new(), // loaded separately via parse_fra_points
    })
}

/// Annex 2A — city-pair flight-level caps.
pub fn parse_level_caps(path: &str) -> Result<Vec<LevelCap>> {
    let rows = rows(path, "Annex 2A")?;
    Ok(rows
        .iter()
        .skip(1) // header
        .filter_map(|r| {
            let from = parse_idents(&cell(r, 4));
            let to = parse_idents(&cell(r, 6));
            let cap_fl = min_fl(&cell(r, 8));
            if from.is_empty() || to.is_empty() || cap_fl.is_none() {
                return None;
            }
            Some(LevelCap {
                id: cell(r, 3),
                from,
                to,
                condition: cell(r, 7),
                cap_fl,
            })
        })
        .collect())
}

/// Lowest flight level mentioned in a capping cell like `FL345` or `FL355FL375`.
fn min_fl(s: &str) -> Option<i32> {
    let up = s.to_uppercase();
    let mut out: Option<i32> = None;
    let mut rest = up.as_str();
    while let Some(pos) = rest.find("FL") {
        rest = &rest[pos + 2..];
        let num: String = rest.chars().take_while(char::is_ascii_digit).collect();
        rest = &rest[num.len()..];
        if let Ok(fl) = num.parse::<i32>() {
            out = Some(out.map_or(fl, |m| m.min(fl)));
        }
    }
    out
}

/// Annex 1 — area definitions.
pub fn parse_areas(path: &str) -> Result<Vec<Area>> {
    let rows = rows(path, "Annex 1")?;
    Ok(rows
        .iter()
        .skip(1) // header
        .filter_map(|r| {
            let id = cell(r, 3);
            let def = cell(r, 4);
            if id.is_empty() {
                return None;
            }
            Some(Area {
                id,
                airports: parse_idents(&def),
                region: cell(r, 6),
            })
        })
        .collect())
}

/// Annex 3B — DCT restrictions.
pub fn parse_dct(path: &str) -> Result<Vec<DctRestriction>> {
    let rows = rows(path, "Annex 3B DCT")?;
    Ok(rows
        .iter()
        .skip(1) // header
        .filter_map(|r| {
            let from = cell(r, 4);
            let to = cell(r, 5);
            if from.is_empty() || to.is_empty() {
                return None;
            }
            let avail = cell(r, 8).to_uppercase();
            Some(DctRestriction {
                id: cell(r, 3),
                from,
                to,
                lower_fl: parse_fl(&cell(r, 6)),
                upper_fl: parse_fl(&cell(r, 7)),
                available: avail.starts_with('Y'),
                utilization: cell(r, 9),
                direction: cell(r, 13),
            })
        })
        .collect())
}

/// Scan Annex 2A/2B/2C for `A DCT B` fix pairs and return the de-duplicated set
/// of allowed FRA direct edges. This is our FRA connectivity catalog: routing
/// through these points/edges is what IFPS accepts in Free Route Airspace.
pub fn parse_fra_edges(path: &str) -> Result<Vec<FraEdge>> {
    use std::collections::HashSet;
    let mut seen: HashSet<FraEdge> = HashSet::new();
    let mut out = Vec::new();
    // Annex 2A/2B/2C hold the enroute FRA routings; Annex 3A DEP/ARR hold the
    // compulsory departure/arrival routings (e.g. LF7352: LFPG deps via
    // `OPALE DCT KESAX DCT DIMAL DCT ALESO`) — both are needed for the graph.
    for sheet in ["Annex 2A", "Annex 2B", "Annex 2C", "Annex 3A DEP", "Annex 3A ARR"] {
        let Ok(rows) = rows(path, sheet) else { continue };
        for row in rows {
            // Normalise separators so `DCT` always stands alone as a token.
            let text = row.join(" ").replace(['(', ')', ',', '\n'], " ");
            let toks: Vec<&str> = text.split_whitespace().collect();
            for w in toks.windows(3) {
                if w[1] == "DCT" && is_fix(w[0]) && is_fix(w[2]) {
                    let e = FraEdge { from: w[0].to_string(), to: w[2].to_string() };
                    if seen.insert(e.clone()) {
                        out.push(e);
                    }
                }
            }
        }
    }
    Ok(out)
}

/// A plausible navaid/waypoint ident: 2–6 chars, letters+digits, ≥1 letter, not
/// a RAD keyword. Excludes airway designators would be nice but they rarely sit
/// on both sides of a literal `DCT`, so the DCT-pair test already filters them.
fn is_fix(s: &str) -> bool {
    let s = s.trim();
    let len = s.len();
    if !(2..=6).contains(&len) {
        return false;
    }
    if !s.chars().all(|c| c.is_ascii_uppercase() || c.is_ascii_digit()) {
        return false;
    }
    if !s.chars().any(|c| c.is_ascii_uppercase()) {
        return false;
    }
    !matches!(
        s,
        "DCT" | "VIA" | "AND" | "THEN" | "ARR" | "DEP" | "EXC" | "RFL" | "BLW"
            | "ABV" | "BTN" | "IAW" | "LOA" | "TFC" | "AVBL" | "NOT" | "ONLY"
            | "H24" | "UFN" | "FL" | "AT" | "IN" | "OR" | "TO" | "VItoken"
    )
}

// ── low-level helpers ──────────────────────────────────────────────────────

/// List the sheet (annex) names in the workbook.
pub fn sheets(path: &str) -> Result<Vec<String>> {
    let wb: Xlsx<_> = open_workbook(path)?;
    Ok(wb.sheet_names().to_vec())
}

/// Dimensions (rows, cols) of a sheet.
pub fn dims(path: &str, sheet: &str) -> Result<(usize, usize)> {
    let mut wb: Xlsx<_> = open_workbook(path)?;
    Ok(wb.worksheet_range(sheet)?.get_size())
}

/// All rows of `sheet` as trimmed strings.
pub fn rows(path: &str, sheet: &str) -> Result<Vec<Vec<String>>> {
    let mut wb: Xlsx<_> = open_workbook(path)?;
    Ok(wb
        .worksheet_range(sheet)?
        .rows()
        .map(|r| r.iter().map(cell_str).collect())
        .collect())
}

/// First `n` rows of `sheet` (for exploration).
pub fn dump(path: &str, sheet: &str, n: usize) -> Result<Vec<Vec<String>>> {
    Ok(rows(path, sheet)?.into_iter().take(n).collect())
}

fn cell(row: &[String], i: usize) -> String {
    row.get(i).cloned().unwrap_or_default().trim().to_string()
}

fn cell_str(c: &Data) -> String {
    match c {
        Data::Empty => String::new(),
        Data::String(s) => s.trim().to_string(),
        Data::Float(f) => f.to_string(),
        Data::Int(i) => i.to_string(),
        Data::Bool(b) => b.to_string(),
        other => other.to_string(),
    }
}

/// First flight level found in a cell like `FL245`, `MEAFL025`, `FL195FL315`.
fn parse_fl(s: &str) -> Option<i32> {
    let up = s.to_uppercase();
    let pos = up.find("FL")?;
    let num: String = up[pos + 2..].chars().take_while(char::is_ascii_digit).collect();
    num.parse().ok()
}

/// Split an Annex-1 definition like `(EGBB, EGBE, EGNX)` into idents.
fn parse_idents(def: &str) -> Vec<String> {
    def.trim()
        .trim_matches(|c| c == '(' || c == ')')
        .split([',', '\n'])
        .map(|s| s.trim().trim_matches(|c| c == '(' || c == ')').to_string())
        .filter(|s| !s.is_empty())
        .collect()
}

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

    /// Parses the real RAD workbook when it's present (CWD = crate dir in tests).
    /// Skips (passes) otherwise so the test stays portable.
    #[test]
    fn parses_real_rad_when_present() {
        let f = "../../rad/RAD_current.xlsx";
        if !std::path::Path::new(f).exists() {
            return;
        }
        let rad = parse(f).unwrap();
        assert!(rad.areas.len() > 50, "areas = {}", rad.areas.len());
        assert!(rad.dct.len() > 1000, "dct = {}", rad.dct.len());
        assert!(rad.dct.iter().any(|d| d.kind() == DctKind::Forbidden));
        assert!(rad.dct.iter().any(|d| d.kind() == DctKind::Compulsory));
        // FL bands parse to plausible values.
        assert!(rad
            .dct
            .iter()
            .filter_map(|d| d.upper_fl)
            .all(|fl| (0..=700).contains(&fl)));
    }

    #[test]
    fn parses_fl_variants() {
        assert_eq!(parse_fl("FL245"), Some(245));
        assert_eq!(parse_fl("MEAFL025"), Some(25));
        assert_eq!(parse_fl("FL195FL315"), Some(195));
        assert_eq!(parse_fl(""), None);
    }
}