qso-graph-trust 0.2.0

// SPDX-License-Identifier: GPL-3.0-or-later
// Copyright (C) 2026 the QSO Graph Trust contributors (see AUTHORS). Part of QSO Graph Trust; see LICENSE.

//! A station location: where the QSOs were made from, as LoTW receives it in a signed log's
//! tSTATION record, and the station's part of every signature. Every field is checked against
//! the configuration's fields for the location's DXCC entity, and a list field's value must be
//! one of its list's.

use std::fmt;

use crate::lotw::{self, FieldKind};

/// The most fields a location is given: more than any DXCC entity's pages hold, all together.
pub const MAX_FIELDS: usize = 32;
/// The longest name or value given, in bytes, checked before anything is copied: longer than any
/// field the configuration defines.
pub const MAX_LEN: usize = 64;

/// A station location, its fields in the order LoTW's configuration lists them.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct StationLocation {
    fields: Vec<(&'static str, String)>,
    dxcc: u32,
}

/// Why a station location is not one LoTW accepts.
#[derive(Clone, Debug, PartialEq, Eq)]
pub enum StationError {
    /// CALL or DXCC is missing.
    Missing(&'static str),
    /// A field given twice.
    Repeated(String),
    /// More than [`MAX_FIELDS`] fields.
    TooManyFields,
    /// A field that is not a location field for this DXCC entity.
    NotAField(String),
    /// A field whose value is not one LoTW accepts.
    Invalid {
        /// The field.
        field: &'static str,
        /// The value given.
        value: String,
    },
}

impl fmt::Display for StationError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Missing(field) => write!(f, "the station location has no {field}"),
            Self::Repeated(field) => write!(f, "the station location gives {field} twice"),
            Self::TooManyFields => write!(f, "the station location has too many fields"),
            Self::NotAField(field) => {
                write!(
                    f,
                    "{field} is not a station-location field for this DXCC entity"
                )
            }
            Self::Invalid { field, value } => {
                write!(f, "{field} {value:?} is not one LoTW accepts")
            }
        }
    }
}

impl std::error::Error for StationError {}

/// The field ADIF's `MY_STATE` fills for this DXCC entity, if it has one.
pub(crate) fn primary_subdivision(dxcc: u32) -> Option<&'static str> {
    lotw::loc_fields_for(dxcc).find(|id| {
        matches!(
            *id,
            "US_STATE"
                | "CA_PROVINCE"
                | "RU_OBLAST"
                | "CN_PROVINCE"
                | "AU_STATE"
                | "JA_PREFECTURE"
                | "FI_KUNTA"
        )
    })
}

/// The field ADIF's `MY_CNTY` fills for this DXCC entity, if it has one.
pub(crate) fn secondary_subdivision(dxcc: u32) -> Option<&'static str> {
    lotw::loc_fields_for(dxcc).find(|id| matches!(*id, "US_COUNTY" | "JA_CITY_GUN_KU"))
}

/// LoTW's value for an ADIF subdivision code, where the two differ (tqslconvert.cpp's aliases).
pub(crate) fn lotw_value<'a>(field: &str, adif: &'a str) -> &'a str {
    match (field, adif) {
        ("CA_PROVINCE", "QC") => "PQ",
        ("CA_PROVINCE", "NL") => "NF",
        ("RU_OBLAST", "YR") => "JA",
        ("RU_OBLAST", "YN") => "JN",
        _ => adif,
    }
}

impl StationLocation {
    /// A station location from a station's ADIF fields, as a logging program keeps them: `MY_DXCC`
    /// (required), `MY_GRIDSQUARE` or `MY_VUCC_GRIDS`, `MY_STATE`, `MY_CNTY` (ADIF's `ST,County`),
    /// `MY_ITU_ZONE`, `MY_CQ_ZONE` and `MY_IOTA`, with the station's call. ADIF has no field for
    /// LoTW's park, which is given on its own. Each value goes to the field signing compares it
    /// with, converted as signing converts it, so a log carrying the same ADIF fields agrees with
    /// the result. A subdivision or park this entity has no field for is left out, as signing leaves
    /// it; any other field is refused.
    pub fn from_adif(
        call: &str,
        adif: &[(&str, &str)],
        park: Option<&str>,
    ) -> Result<Self, StationError> {
        let get = |name: &str| {
            adif.iter()
                .find(|(n, _)| n.eq_ignore_ascii_case(name))
                .map(|(_, v)| v.trim())
                .filter(|v| !v.is_empty())
        };
        if let Some((name, _)) = adif.iter().find(|(n, _)| {
            ![
                "MY_DXCC",
                "MY_GRIDSQUARE",
                "MY_VUCC_GRIDS",
                "MY_STATE",
                "MY_CNTY",
                "MY_ITU_ZONE",
                "MY_CQ_ZONE",
                "MY_IOTA",
            ]
            .iter()
            .any(|known| known.eq_ignore_ascii_case(n))
        }) {
            return Err(StationError::NotAField(
                name.chars().take(MAX_LEN).collect(),
            ));
        }
        let dxcc_text = get("MY_DXCC").ok_or(StationError::Missing("DXCC"))?;
        let dxcc = dxcc_text
            .parse::<u32>()
            .map_err(|_| StationError::Invalid {
                field: "DXCC",
                value: dxcc_text.chars().take(MAX_LEN).collect(),
            })?;
        let dxcc_text = dxcc.to_string();
        let mut fields: Vec<(&str, String)> = vec![("CALL", call.to_owned()), ("DXCC", dxcc_text)];
        if let Some(grid) = get("MY_VUCC_GRIDS").or_else(|| get("MY_GRIDSQUARE")) {
            fields.push(("GRIDSQUARE", grid.to_owned()));
        }
        if let (Some(field), Some(value)) = (primary_subdivision(dxcc), get("MY_STATE")) {
            fields.push((field, lotw_value(field, value).to_owned()));
        }
        if let (Some(field), Some(value)) = (secondary_subdivision(dxcc), get("MY_CNTY")) {
            let county = value.split_once(',').map_or(value, |(_, c)| c.trim());
            fields.push((field, county.to_owned()));
        }
        for (field, name) in [("ITUZ", "MY_ITU_ZONE"), ("CQZ", "MY_CQ_ZONE")] {
            if let Some(value) = get(name) {
                let number = value
                    .parse::<u32>()
                    .map_or(value.to_owned(), |n| n.to_string());
                fields.push((field, number));
            }
        }
        if let Some(iota) = get("MY_IOTA") {
            fields.push(("IOTA", iota.to_owned()));
        }
        if let Some(park) = park.map(str::trim).filter(|p| !p.is_empty())
            && let Some(field) = lotw::loc_fields_for(dxcc)
                .find(|id| matches!(*id, "US_PARK" | "CA_US_PARK" | "DX_US_PARK"))
        {
            fields.push((field, park.to_owned()));
        }
        let given: Vec<(&str, &str)> = fields.iter().map(|(n, v)| (*n, v.as_str())).collect();
        Self::new(&given)
    }

    /// A station location from its fields, named as LoTW names them (`CALL`, `DXCC`,
    /// `GRIDSQUARE`, `US_STATE`, …). Empty values are left out.
    pub fn new(given: &[(&str, &str)]) -> Result<Self, StationError> {
        if given.len() > MAX_FIELDS {
            return Err(StationError::TooManyFields);
        }
        if let Some((name, v)) = given
            .iter()
            .find(|(n, v)| n.len() > MAX_LEN || v.len() > MAX_LEN)
        {
            return Err(match lotw::loc_field(name) {
                Some(f) => invalid(f.id, v),
                None => StationError::NotAField(name.chars().take(MAX_LEN).collect()),
            });
        }
        let value = |name: &str| {
            given
                .iter()
                .find(|(n, _)| *n == name)
                .map(|(_, v)| v.trim())
                .filter(|v| !v.is_empty())
        };
        let dxcc_text = value("DXCC").ok_or(StationError::Missing("DXCC"))?;
        let dxcc = dxcc_text
            .parse::<u32>()
            .ok()
            .filter(|&id| id != 0 && lotw::dxcc(id).is_some())
            .ok_or_else(|| invalid("DXCC", dxcc_text))?;
        value("CALL").ok_or(StationError::Missing("CALL"))?;

        let allowed: Vec<&'static str> = lotw::loc_fields_for(dxcc)
            .filter(|f| lotw::loc_field(f).is_some_and(|f| f.shown))
            .collect();
        if let Some((name, _)) = given.iter().find(|(n, _)| !allowed.contains(n)) {
            return Err(StationError::NotAField(name.to_string()));
        }
        for (i, (name, _)) in given.iter().enumerate() {
            if given[..i].iter().any(|(n, _)| n == name) {
                return Err(StationError::Repeated(name.to_string()));
            }
        }

        let mut fields: Vec<(&'static str, String)> = Vec::new();
        // The zones the entity, and each list value that says so, lie in.
        let mut zone_maps = vec![lotw::dxcc(dxcc).map_or("", |e| e.zones)];
        for id in allowed {
            let Some(v) = value(id) else { continue };
            let field = lotw::loc_field(id).ok_or(StationError::NotAField(id.to_string()))?;
            let v = match field.kind {
                FieldKind::Int => {
                    let n: i64 = v.parse().map_err(|_| invalid(id, v))?;
                    if field.range.is_some_and(|(lo, hi)| !(lo..=hi).contains(&n)) {
                        return Err(invalid(id, v));
                    }
                    n.to_string()
                }
                FieldKind::Text if v.chars().count() > field.len => return Err(invalid(id, v)),
                FieldKind::Text if lotw::is_list(id) => {
                    let dependency = match field.depends_on {
                        None => String::new(),
                        Some("DXCC") => dxcc.to_string(),
                        Some(other) => fields
                            .iter()
                            .find(|(n, _)| *n == other)
                            .map(|(_, v)| v.clone())
                            .unwrap_or_default(),
                    };
                    let known = lotw::loc_values(id, &dependency)
                        .find(|known| known.eq_ignore_ascii_case(v))
                        .ok_or_else(|| invalid(id, v))?;
                    zone_maps.push(lotw::loc_value_zones(id, &dependency, known));
                    known.to_string()
                }
                FieldKind::Text => {
                    let v = v.to_ascii_uppercase();
                    let ok = match id {
                        "CALL" => crate::qso::is_callsign(&v),
                        "GRIDSQUARE" => is_grid_list(&v),
                        "IOTA" => is_iota(&v),
                        _ => true,
                    };
                    if !ok {
                        return Err(invalid(id, &v));
                    }
                    v
                }
            };
            fields.push((id, v));
        }
        let zone = |name: &str| {
            fields
                .iter()
                .find(|(n, _)| *n == name)
                .and_then(|(_, v)| v.parse::<u32>().ok())
        };
        let (itu, cq) = (zone("ITUZ"), zone("CQZ"));
        // Each zone map that applies must hold a pair matching the zones given: the location's
        // zones are where its entity, state and the rest are, as ARRL's configuration says.
        let fits = |map: &&str| {
            map.is_empty()
                || lotw::zone_pairs(map)
                    .any(|(i, c)| itu.is_none_or(|z| z == i) && cq.is_none_or(|z| z == c))
        };
        if (itu.is_some() || cq.is_some()) && !zone_maps.iter().all(fits) {
            let shown = format!(
                "ITUZ {} CQZ {}",
                itu.map_or("-".into(), |z| z.to_string()),
                cq.map_or("-".into(), |z| z.to_string())
            );
            return Err(StationError::Invalid {
                field: "ZONES",
                value: shown,
            });
        }
        Ok(Self { fields, dxcc })
    }

    /// Whether this grid is one of the location's, compared as precisely as both are given: a
    /// subsquare against a subsquare, else the square.
    fn has_grid(&self, grid: &str) -> bool {
        self.get("GRIDSQUARE").is_some_and(|grids| {
            grids.split(',').map(str::trim).any(|ours| {
                let n = ours.len().min(grid.len());
                n >= 2
                    && ours
                        .get(..n)
                        .zip(grid.get(..n))
                        .is_some_and(|(a, b)| a.eq_ignore_ascii_case(b))
            })
        })
    }

    /// Whether a QSO record's own word about its station, an ADIF field from
    /// [`crate::qso::STATION_FIELDS`] in capitals, disagrees with this location. A field the
    /// location has nothing to compare with disagrees too: the QSO says more than the location can
    /// confirm, so it is not signed for it.
    pub fn contradicts(&self, adif: &str, value: &str) -> bool {
        let same = |field: &str| {
            self.get(field)
                .is_some_and(|v| v.eq_ignore_ascii_case(value))
        };
        let number = |field: &str| {
            let ours = self.get(field).and_then(|v| v.parse::<u32>().ok());
            ours.is_some() && ours == value.parse().ok()
        };
        let agrees = match adif {
            "STATION_CALLSIGN" | "OPERATOR" => same("CALL"),
            "MY_DXCC" => value.parse() == Ok(self.dxcc),
            "MY_CQ_ZONE" => number("CQZ"),
            "MY_ITU_ZONE" => number("ITUZ"),
            "MY_IOTA" => same("IOTA"),
            "MY_GRIDSQUARE" => self.has_grid(value),
            // A VUCC QSO's squares must be the location's squares, all of them and no others.
            "MY_VUCC_GRIDS" => {
                let squares = |list: &str| {
                    let mut s: Vec<String> = list
                        .split(',')
                        .filter_map(|g| g.trim().get(..4).map(str::to_ascii_uppercase))
                        .collect();
                    s.sort_unstable();
                    s.dedup();
                    s
                };
                self.get("GRIDSQUARE")
                    .is_some_and(|ours| squares(ours) == squares(value))
            }
            "MY_STATE" => SUBDIVISIONS.iter().any(|f| same(f)),
            // ADIF writes a US county as "KS,Sedgwick": the state, if given, must agree too.
            "MY_CNTY" => {
                let (state, county) = match value.split_once(',') {
                    Some((st, c)) => (Some(st.trim()), c.trim()),
                    None => (None, value.trim()),
                };
                let county_ok = ["US_COUNTY", "JA_CITY_GUN_KU"]
                    .iter()
                    .any(|f| self.get(f).is_some_and(|v| v.eq_ignore_ascii_case(county)));
                let state_ok = state.is_none_or(|st| {
                    SUBDIVISIONS
                        .iter()
                        .any(|f| self.get(f).is_some_and(|v| v.eq_ignore_ascii_case(st)))
                });
                county_ok && state_ok
            }
            _ => false,
        };
        !agrees
    }

    /// The location's fields, in the order its tSTATION record lists them.
    pub fn fields(&self) -> impl Iterator<Item = (&'static str, &str)> {
        self.fields.iter().map(|(n, v)| (*n, v.as_str()))
    }

    /// One field's value.
    pub fn get(&self, name: &str) -> Option<&str> {
        self.fields
            .iter()
            .find(|(n, _)| *n == name)
            .map(|(_, v)| v.as_str())
    }

    /// The station's callsign.
    pub fn call(&self) -> &str {
        self.get("CALL").unwrap_or_default()
    }

    /// The station's DXCC entity.
    pub fn dxcc(&self) -> u32 {
        self.dxcc
    }

    /// The fields the signature covers, in the signature specification's order: the station's
    /// part of what is signed, before each QSO's. Not yet in capitals; the whole string is.
    pub fn sign_data(&self) -> String {
        lotw::SIGN_STATION
            .iter()
            .filter_map(|name| self.get(name))
            .collect()
    }
}

/// The DXCC entity's name in ARRL's configuration, or `None` for a number it does not list.
pub fn dxcc_name(dxcc: u32) -> Option<&'static str> {
    lotw::dxcc(dxcc).map(|e| e.name)
}

/// The fields a station location for this DXCC entity may give, in the order a location lists
/// them, as [`StationLocation::new`] accepts them. Empty for a number ARRL does not list.
pub fn fields_for(dxcc: u32) -> Vec<&'static str> {
    if dxcc == 0 || lotw::dxcc(dxcc).is_none() {
        return Vec::new();
    }
    lotw::loc_fields_for(dxcc)
        .filter(|f| lotw::loc_field(f).is_some_and(|f| f.shown))
        .collect()
}

/// The error for a value, shown cut to [`MAX_LEN`] characters, so an error is never large.
fn invalid(field: &'static str, value: &str) -> StationError {
    StationError::Invalid {
        field,
        value: value.chars().take(MAX_LEN).collect(),
    }
}

/// A location's grid, or the grids of one on a boundary, as ARRL's station-location rules allow
/// them: one locator (`EM17`, `EM17AB`), two squares that share an edge (`EM17,EM18`), or four
/// that meet at a corner (`EM17,EM18,EM27,EM28`).
pub(crate) fn is_grid_list(s: &str) -> bool {
    let grids: Vec<&str> = s.split(',').map(str::trim).collect();
    if let [one] = grids[..] {
        return is_grid(one);
    }
    let Some(mut squares) = grids.iter().map(|g| square(g)).collect::<Option<Vec<_>>>() else {
        return false;
    };
    squares.sort_unstable();
    squares.dedup();
    if squares.len() != grids.len() {
        return false;
    }
    // Longitude wraps at the antimeridian; latitude does not.
    let next_lon = |a: u32, b: u32| (a + 1) % 180 == b || (b + 1) % 180 == a;
    let next_lat = |a: u32, b: u32| a.abs_diff(b) == 1;
    match squares[..] {
        [(lon_a, lat_a), (lon_b, lat_b)] => {
            (lat_a == lat_b && next_lon(lon_a, lon_b)) || (lon_a == lon_b && next_lat(lat_a, lat_b))
        }
        [a, b, c, d] => {
            let mut lons: Vec<u32> = vec![a.0, b.0, c.0, d.0];
            let mut lats: Vec<u32> = vec![a.1, b.1, c.1, d.1];
            lons.sort_unstable();
            lons.dedup();
            lats.sort_unstable();
            lats.dedup();
            // Four distinct squares on two longitudes and two latitudes are the 2x2 block.
            matches!((&lons[..], &lats[..]), ([x, y], [p, q]) if next_lon(*x, *y) && next_lat(*p, *q))
        }
        _ => false,
    }
}

/// A locator as ADIF writes one in capitals: a field (`EM`), square (`EM17`), subsquare
/// (`EM17AB`) or extended square (`EM17AB12`).
pub(crate) fn is_adif_grid(g: &str) -> bool {
    let b = g.as_bytes();
    let pair =
        |i: usize, ok: fn(&u8) -> bool| b.get(i).is_some_and(ok) && b.get(i + 1).is_some_and(ok);
    let field = |c: &u8| (b'A'..=b'R').contains(c);
    let sub = |c: &u8| (b'A'..=b'X').contains(c);
    let digit = |c: &u8| c.is_ascii_digit();
    matches!(b.len(), 2 | 4 | 6 | 8)
        && pair(0, field)
        && (b.len() < 4 || pair(2, digit))
        && (b.len() < 6 || pair(4, sub))
        && (b.len() < 8 || pair(6, digit))
}

/// ADIF's MY_VUCC_GRIDS: two or four locators of a square or finer whose squares are a grid list
/// [`is_grid_list`] accepts.
pub(crate) fn is_adif_vucc_grids(s: &str) -> bool {
    let grids: Vec<&str> = s.split(',').map(str::trim).collect();
    matches!(grids.len(), 2 | 4)
        && grids.iter().all(|g| g.len() >= 4 && is_adif_grid(g))
        && is_grid_list(&grids.iter().map(|g| &g[..4]).collect::<Vec<_>>().join(","))
}

/// A square, `EM17`, as (longitude, latitude) in squares from 180W and 90S.
fn square(g: &str) -> Option<(u32, u32)> {
    let b = g.as_bytes();
    (b.len() == 4 && is_grid(g)).then(|| {
        let lon = u32::from(b[0] - b'A') * 10 + u32::from(b[2] - b'0');
        let lat = u32::from(b[1] - b'A') * 10 + u32::from(b[3] - b'0');
        (lon, lat)
    })
}

/// One Maidenhead locator in capitals, `EM17` or `EM17AB`. Read as bytes, so any input is safe.
pub(crate) fn is_grid(g: &str) -> bool {
    let b = g.as_bytes();
    let field = |c: u8| (b'A'..=b'R').contains(&c);
    let sub = |c: u8| (b'A'..=b'X').contains(&c);
    let square = b.len() >= 4
        && field(b[0])
        && field(b[1])
        && b[2].is_ascii_digit()
        && b[3].is_ascii_digit();
    match b.len() {
        4 => square,
        6 => square && sub(b[4]) && sub(b[5]),
        _ => false,
    }
}

/// The location fields that are a DXCC entity's first subdivision, which ADIF's MY_STATE names.
const SUBDIVISIONS: [&str; 7] = [
    "US_STATE",
    "CA_PROVINCE",
    "AU_STATE",
    "CN_PROVINCE",
    "RU_OBLAST",
    "JA_PREFECTURE",
    "FI_KUNTA",
];

/// An IOTA reference: a continent and three digits, as `NA-001`.
fn is_iota(s: &str) -> bool {
    let (cont, num) = s.split_once('-').unwrap_or(("", ""));
    ["AF", "AN", "AS", "EU", "NA", "OC", "SA"].contains(&cont)
        && num.len() == 3
        && num.bytes().all(|b| b.is_ascii_digit())
}

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

    #[test]
    fn an_entitys_name_is_arrls_and_a_number_it_does_not_list_has_none() {
        assert_eq!(dxcc_name(291), Some("UNITED STATES OF AMERICA"));
        assert_eq!(dxcc_name(1), Some("CANADA"));
        // A number ARRL does not list has no name, and no fields.
        assert_eq!(dxcc_name(100_000), None);
        assert!(fields_for(100_000).is_empty());
    }

    #[test]
    fn a_qsos_word_about_its_station_must_agree_with_the_location() {
        let loc = StationLocation::new(KANSAS).expect("location");
        for (adif, value) in [
            ("STATION_CALLSIGN", "QG0TEST"),
            ("MY_DXCC", "291"),
            ("MY_GRIDSQUARE", "EM17AB"),
            ("MY_STATE", "KS"),
            ("MY_CNTY", "KS,SEDGWICK"),
            ("MY_CNTY", "SEDGWICK"),
            ("MY_CQ_ZONE", "04"),
            ("MY_ITU_ZONE", "7"),
            ("MY_VUCC_GRIDS", "EM17"),
            ("OPERATOR", "QG0TEST"),
        ] {
            assert!(!loc.contradicts(adif, value), "{adif} {value}");
        }
        // Found in review: a two-grid QSO passed for a four-grid location.
        let mut block = KANSAS.to_vec();
        block[4] = ("GRIDSQUARE", "EM17,EM18,EM27,EM28");
        let block = StationLocation::new(&block).expect("location");
        assert!(block.contradicts("MY_VUCC_GRIDS", "EM17,EM18"));
        assert!(!block.contradicts("MY_VUCC_GRIDS", "EM28,EM27AX,EM18,EM17"));
        // ADIF's finer precision, compared as precisely as both are given.
        assert!(!loc.contradicts("MY_GRIDSQUARE", "EM17AB12"));
        assert!(!loc.contradicts("MY_GRIDSQUARE", "EM"));
        assert!(
            is_adif_grid("EM17AB12")
                && is_adif_grid("EM")
                && !is_adif_grid("EM1")
                && !is_adif_grid("EM17AB1X")
        );
        assert!(
            is_adif_vucc_grids("EM17AX,EM18AA")
                && !is_adif_vucc_grids("EM17")
                && !is_adif_vucc_grids("EM17,FN31")
        );
        // Found in review: subsquares that differ were compared only as squares.
        let mut fine = KANSAS.to_vec();
        fine[4] = ("GRIDSQUARE", "EM17AB");
        let fine = StationLocation::new(&fine).expect("location");
        assert!(!fine.contradicts("MY_GRIDSQUARE", "EM17AB"));
        assert!(!fine.contradicts("MY_GRIDSQUARE", "EM17"));
        assert!(fine.contradicts("MY_GRIDSQUARE", "EM17CD"));
        let huge = "A".repeat(MAX_LEN + 1);
        let mut given = KANSAS.to_vec();
        given[4] = ("GRIDSQUARE", &huge);
        assert!(matches!(
            StationLocation::new(&given),
            Err(StationError::Invalid { field: "GRIDSQUARE", value }) if value.len() == MAX_LEN
        ));
        for (adif, value) in [
            ("STATION_CALLSIGN", "QG1TEST"),
            ("MY_DXCC", "1"),
            ("MY_GRIDSQUARE", "FN03"),
            ("MY_STATE", "SC"),
            ("MY_CNTY", "SC,SEDGWICK"),
            ("MY_CNTY", "CHARLESTON"),
            ("MY_CQ_ZONE", "5"),
            ("MY_ITU_ZONE", "8"),
            // The location has no IOTA, so a QSO naming one is not signed for it.
            ("MY_IOTA", "NA-110"),
            ("MY_VUCC_GRIDS", "EM17,EM18"),
            ("OPERATOR", "QG1TEST"),
            ("NOT_A_FIELD", "x"),
        ] {
            assert!(loc.contradicts(adif, value), "{adif} {value}");
        }
    }

    const KANSAS: &[(&str, &str)] = &[
        ("CALL", "QG0TEST"),
        ("DXCC", "291"),
        ("US_STATE", "KS"),
        ("US_COUNTY", "Sedgwick"),
        ("GRIDSQUARE", "EM17"),
        ("CQZ", "4"),
        ("ITUZ", "7"),
    ];

    #[test]
    fn fields_are_listed_in_the_configurations_order() {
        let loc = StationLocation::new(KANSAS).expect("location");
        let names: Vec<&str> = loc.fields().map(|(n, _)| n).collect();
        assert_eq!(
            names,
            [
                "CALL",
                "DXCC",
                "GRIDSQUARE",
                "ITUZ",
                "CQZ",
                "US_STATE",
                "US_COUNTY"
            ]
        );
        assert_eq!(loc.sign_data(), "4EM177SedgwickKS");
        assert_eq!((loc.call(), loc.dxcc()), ("QG0TEST", 291));
    }

    #[test]
    fn list_values_are_matched_and_written_as_the_list_writes_them() {
        let mut given = KANSAS.to_vec();
        given[3] = ("US_COUNTY", "SEDGWICK");
        let loc = StationLocation::new(&given).expect("location");
        assert_eq!(loc.get("US_COUNTY"), Some("Sedgwick"));
        // A county of another state is not one of Kansas's.
        given[3] = ("US_COUNTY", "Charleston");
        assert!(matches!(
            StationLocation::new(&given),
            Err(StationError::Invalid {
                field: "US_COUNTY",
                ..
            })
        ));
    }

    #[test]
    fn what_lotw_would_refuse_is_refused() {
        let with = |name: &'static str, value: &'static str| {
            let mut given: Vec<(&str, &str)> =
                KANSAS.iter().filter(|(n, _)| *n != name).copied().collect();
            given.push((name, value));
            StationLocation::new(&given)
        };
        assert!(matches!(
            with("CQZ", "41"),
            Err(StationError::Invalid { field: "CQZ", .. })
        ));
        assert!(matches!(
            with("ITUZ", "x"),
            Err(StationError::Invalid { field: "ITUZ", .. })
        ));
        assert!(matches!(
            with("GRIDSQUARE", "ZZ17"),
            Err(StationError::Invalid { .. })
        ));
        assert!(matches!(
            with("US_STATE", "XX"),
            Err(StationError::Invalid { .. })
        ));
        assert!(matches!(
            with("DXCC", "9999"),
            Err(StationError::Invalid { field: "DXCC", .. })
        ));
        assert_eq!(
            with("CA_PROVINCE", "ON"),
            Err(StationError::NotAField("CA_PROVINCE".into()))
        );
        assert_eq!(
            with("ZERR", "x"),
            Err(StationError::NotAField("ZERR".into()))
        );
        assert_eq!(
            StationLocation::new(&[("DXCC", "291")]),
            Err(StationError::Missing("CALL"))
        );
        assert_eq!(
            StationLocation::new(&[("CALL", "QG0TEST"), ("CALL", "QG0TEST"), ("DXCC", "291")]),
            Err(StationError::Repeated("CALL".into()))
        );
        assert!(with("GRIDSQUARE", "EM17,EM18").is_ok());
        assert!(with("GRIDSQUARE", "EM17,EM27").is_ok());
        assert!(with("GRIDSQUARE", "EM19,EN10").is_ok());
        assert!(with("GRIDSQUARE", "EM17,EM18,EM27,EM28").is_ok());
        // Found in review: grids that do not meet were accepted as one location.
        for bad in [
            "EM17,FN31",
            "EM17,EM18,EM19",
            "EM17,EM17",
            "EM17,EM28",
            "EM17AB,EM18",
            "EM17,EM18,EM27,EM29",
        ] {
            assert!(
                matches!(with("GRIDSQUARE", bad), Err(StationError::Invalid { .. })),
                "{bad}"
            );
        }
        // Found in review: zones the entity does not lie in were accepted.
        assert!(matches!(
            with("CQZ", "25"),
            Err(StationError::Invalid { field: "ZONES", .. })
        ));
        // Kansas is ITU 7, CQ 4: ITU 8 is the USA's, but not Kansas's.
        assert!(matches!(
            with("ITUZ", "8"),
            Err(StationError::Invalid { field: "ZONES", .. })
        ));
        // Found in review: a six-byte grid with a two-byte character inside panicked on slicing.
        assert!(matches!(
            with("GRIDSQUARE", "AAA\u{e9}A"),
            Err(StationError::Invalid { .. })
        ));
        let many: Vec<(String, &str)> = (0..=MAX_FIELDS).map(|i| (format!("X{i}"), "")).collect();
        let many: Vec<(&str, &str)> = many.iter().map(|(n, v)| (n.as_str(), *v)).collect();
        assert_eq!(
            StationLocation::new(&many),
            Err(StationError::TooManyFields)
        );
        assert!(with("IOTA", "NA-110").is_ok());
        assert!(with("IOTA", "NA-1").is_err());
    }
}