//! Atlas data-delivery proxy (T-949) — two thin, independent endpoints
//! alongside the per-body layer-stream proxy ([`crate::atlas::layer_proxy`]):
//!
//! - **Star map** ([`StarMapRequest`]/[`StarMapResponse`]): a session-scoped,
//!   non-per-body proxy over the static `client/data/star_map_data.json`
//!   dataset (produced by `tooling/generate-star-map-data.py`). Reads the file
//!   fresh on every request — no caching, no staleness handling — because the
//!   client only asks once per session when the Atlas star-map view opens.
//!   The parsed JSON is passed through as an opaque `serde_json::Value` rather
//!   than a hand-mirrored Rust struct: the server has no reason to understand
//!   `_meta`/`nodes`/`edges`, so this stays a genuinely thin proxy that never
//!   needs a code change when the generator's JSON shape evolves.
//!
//! - **City names** ([`CityNamesRequest`]/[`CityNamesResponse`]): a per-body
//!   names-only settlement list read straight from `atlas_city_names`
//!   (replaces the client's legacy `markers.json` names-only read, D-223, for
//!   every body except Sol). Available immediately — it does not wait on the
//!   generation cascade the way `AtlasLayerResponse.settlements` does.
//!
//! **Sol exclusion (D-236):** Sol (system `GJ-0`) is permanently out of the
//! generation cascade. `handle_city_names_request` checks
//! [`CityContextReader::is_sol_body`] first and returns
//! [`CityNamesStatus::SolExcluded`] with an empty city list — the client keeps
//! its legacy authored `markers.json` read for Sol; this proxy never runs Sol
//! through any cascade or DB-derived path.
//!
//! **Inbound demux (D-225 extension):** the existing array-vs-map trick
//! (`Vec<PlayerInput>` vs. `AtlasLayerRequest`) is preserved byte-for-byte —
//! neither request type gained fields. The two new map shapes each carry a
//! **mandatory boolean discriminator field** (`star_map` / `city_names`)
//! instead of relying on "which optional field is missing" trial-order
//! fragility: `CityNamesRequest{city_names: bool, body_id: String}` and
//! `AtlasLayerRequest{body_id: String, up_to: CascadeLayer}` both key on
//! `body_id`, and serde's derived `Deserialize` silently ignores unknown
//! fields by default — so a payload carrying every field either shape wants
//! would ambiguously satisfy both if disambiguation relied on "does this
//! parse at all". Requiring a field the *other* shapes don't have at all
//! (missing required field ⇒ hard deserialize failure, not silent ignore)
//! keeps every shape mutually exclusive without adding `#[serde(deny_unknown_fields)]`
//! to `AtlasLayerRequest` (which would risk breaking any already-deployed
//! client encoder that harmlessly sends extra fields). See
//! `crate::bridge::decode_inbound` for the trial order + full rationale.

use std::path::{Path, PathBuf};

use bevy_ecs::prelude::Resource;
use serde::{Deserialize, Serialize};

use crate::atlas::city_context_reader::CityContextReader;

// ---------------------------------------------------------------------------
// Star map proxy
// ---------------------------------------------------------------------------

/// A client request for the star-map dataset (T-949a). Non-per-body — the
/// map contains every system in the Reach.
///
/// `star_map` is the Inbound discriminator (see module doc): always `true`.
/// Its presence, not its value, is what disambiguates this map shape.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct StarMapRequest {
    pub star_map: bool,
}

/// Status of a [`StarMapResponse`].
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub enum StarMapStatus {
    /// The dataset was read and parsed (`data` is populated).
    Ready,
    /// IO or JSON-parse failure (message for the client log). The client
    /// should keep using whatever it already has (or its own bundled copy)
    /// rather than treat this as fatal.
    Error(String),
}

/// A star-map response: the parsed `star_map_data.json` contents verbatim, or
/// an error status (T-949a).
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct StarMapResponse {
    pub status: StarMapStatus,
    /// Verbatim parsed JSON (`_meta`, `nodes`, `edges` — see
    /// `tooling/generate-star-map-data.py`), re-serialized as MessagePack.
    /// `None` unless `status == Ready`.
    pub data: Option<serde_json::Value>,
}

/// Resolved path to `client/data/star_map_data.json` (T-949a). A thin resource
/// holding just the path — the file is re-read fresh on every request (no
/// caching, per the ticket: this is a one-shot-per-session read from the
/// client, so staleness handling would be pure complexity for no benefit).
#[derive(Resource, Debug, Clone)]
pub struct StarMapDataPath(pub PathBuf);

/// Serve one star-map request (T-949a): read + parse the file fresh.
pub fn handle_star_map_request(_req: &StarMapRequest, path: &Path) -> StarMapResponse {
    match std::fs::read_to_string(path) {
        Ok(text) => match serde_json::from_str::<serde_json::Value>(&text) {
            Ok(data) => StarMapResponse {
                status: StarMapStatus::Ready,
                data: Some(data),
            },
            Err(e) => StarMapResponse {
                status: StarMapStatus::Error(format!("star_map_data.json parse error: {e}")),
                data: None,
            },
        },
        Err(e) => StarMapResponse {
            status: StarMapStatus::Error(format!(
                "star_map_data.json read error ({}): {e}",
                path.display()
            )),
            data: None,
        },
    }
}

// ---------------------------------------------------------------------------
// City names proxy
// ---------------------------------------------------------------------------

/// A client request for a body's authored settlement names (T-949b).
///
/// `city_names` is the Inbound discriminator (see module doc): always `true`.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct CityNamesRequest {
    pub city_names: bool,
    pub body_id: String,
}

/// Status of a [`CityNamesResponse`].
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub enum CityNamesStatus {
    /// Names are ready (`cities` is populated; legitimately empty for a body
    /// with no authored settlements).
    Ready,
    /// D-236: `body_id` is a Sol body. Sol is permanently out of the
    /// generation cascade and every DB-derived Atlas path — the client must
    /// keep its legacy authored `markers.json` read for Sol. `cities` is empty.
    SolExcluded,
    /// DB/IO failure reading `atlas_city_names` (message for the client log).
    Error(String),
}

/// One settlement name entry (T-949b) — see
/// [`crate::atlas::city_context_reader::CityNameRow`] for the reader-side row
/// this is built from.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct CityNameEntry {
    pub city_id: u64,
    pub name: String,
    pub is_capital: bool,
}

/// A city-names response: the body's authored settlements, or a non-ready
/// status (T-949b).
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct CityNamesResponse {
    pub body_id: String,
    pub status: CityNamesStatus,
    pub cities: Vec<CityNameEntry>,
}

/// Serve one city-names request (T-949b): D-236 Sol check first, then the
/// names-only `atlas_city_names` read. `city_reader` absent (no DB opened at
/// startup) is reported as `Error`, matching `layer_proxy`'s "no body source
/// resolver" convention.
pub fn handle_city_names_request(
    req: &CityNamesRequest,
    city_reader: Option<&CityContextReader>,
) -> CityNamesResponse {
    let Some(reader) = city_reader else {
        return CityNamesResponse {
            body_id: req.body_id.clone(),
            status: CityNamesStatus::Error("city context reader unavailable".to_string()),
            cities: Vec::new(),
        };
    };

    match reader.is_sol_body(&req.body_id) {
        Ok(true) => {
            return CityNamesResponse {
                body_id: req.body_id.clone(),
                status: CityNamesStatus::SolExcluded,
                cities: Vec::new(),
            };
        }
        Ok(false) => {}
        Err(e) => {
            return CityNamesResponse {
                body_id: req.body_id.clone(),
                status: CityNamesStatus::Error(e.to_string()),
                cities: Vec::new(),
            };
        }
    }

    match reader.read_body_city_names(&req.body_id) {
        Ok(rows) => CityNamesResponse {
            body_id: req.body_id.clone(),
            status: CityNamesStatus::Ready,
            cities: rows
                .into_iter()
                .map(|r| CityNameEntry {
                    city_id: r.city_id,
                    name: r.name,
                    is_capital: r.is_capital,
                })
                .collect(),
        },
        Err(e) => CityNamesResponse {
            body_id: req.body_id.clone(),
            status: CityNamesStatus::Error(e.to_string()),
            cities: Vec::new(),
        },
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use rusqlite::Connection;
    use std::sync::atomic::{AtomicU32, Ordering};

    static SEQ: AtomicU32 = AtomicU32::new(0);

    // ─── StarMapRequest/Response ─────────────────────────────────────────────

    #[test]
    fn star_map_request_round_trips_msgpack() {
        let req = StarMapRequest { star_map: true };
        let bytes = rmp_serde::to_vec_named(&req).expect("encode");
        let decoded: StarMapRequest = rmp_serde::from_slice(&bytes).expect("decode");
        assert!(decoded.star_map);
    }

    #[test]
    fn handle_star_map_request_reads_and_parses_file() {
        let n = SEQ.fetch_add(1, Ordering::Relaxed);
        let path = std::env::temp_dir().join(format!("sr_starmap_{}_{n}.json", std::process::id()));
        std::fs::write(
            &path,
            r#"{"_meta": {"v": 1}, "nodes": [1, 2], "edges": []}"#,
        )
        .expect("write fixture json");

        let resp = handle_star_map_request(&StarMapRequest { star_map: true }, &path);
        assert_eq!(resp.status, StarMapStatus::Ready);
        let data = resp.data.as_ref().expect("data present on Ready");
        assert_eq!(data["nodes"][0], 1);

        // Round trip the whole response through MessagePack too (the actual
        // wire path).
        let bytes = rmp_serde::to_vec_named(&resp).expect("encode");
        let decoded: StarMapResponse = rmp_serde::from_slice(&bytes).expect("decode");
        assert_eq!(decoded.status, StarMapStatus::Ready);
        assert_eq!(decoded.data.unwrap()["nodes"][1], 2);

        let _ = std::fs::remove_file(&path);
    }

    #[test]
    fn handle_star_map_request_missing_file_is_error_not_panic() {
        let path = PathBuf::from("/nonexistent/sr-test/star_map_data.json");
        let resp = handle_star_map_request(&StarMapRequest { star_map: true }, &path);
        assert!(matches!(resp.status, StarMapStatus::Error(_)));
        assert!(resp.data.is_none());
    }

    #[test]
    fn handle_star_map_request_malformed_json_is_error() {
        let n = SEQ.fetch_add(1, Ordering::Relaxed);
        let path =
            std::env::temp_dir().join(format!("sr_starmap_bad_{}_{n}.json", std::process::id()));
        std::fs::write(&path, "{ not valid json").expect("write fixture json");

        let resp = handle_star_map_request(&StarMapRequest { star_map: true }, &path);
        assert!(matches!(resp.status, StarMapStatus::Error(_)));
        assert!(resp.data.is_none());

        let _ = std::fs::remove_file(&path);
    }

    // ─── CityNamesRequest/Response ───────────────────────────────────────────

    #[test]
    fn city_names_request_round_trips_msgpack() {
        let req = CityNamesRequest {
            city_names: true,
            body_id: "GJ1c".into(),
        };
        let bytes = rmp_serde::to_vec_named(&req).expect("encode");
        let decoded: CityNamesRequest = rmp_serde::from_slice(&bytes).expect("decode");
        assert!(decoded.city_names);
        assert_eq!(decoded.body_id, "GJ1c");
    }

    #[test]
    fn city_names_response_round_trips_msgpack() {
        let resp = CityNamesResponse {
            body_id: "GJ1c".into(),
            status: CityNamesStatus::Ready,
            cities: vec![CityNameEntry {
                city_id: 1,
                name: "Port Aldren".into(),
                is_capital: true,
            }],
        };
        let bytes = rmp_serde::to_vec_named(&resp).expect("encode");
        let decoded: CityNamesResponse = rmp_serde::from_slice(&bytes).expect("decode");
        assert_eq!(decoded.status, CityNamesStatus::Ready);
        assert_eq!(decoded.cities[0].name, "Port Aldren");
        assert!(decoded.cities[0].is_capital);
    }

    /// Minimal db mirroring what `is_sol_body` + `read_body_city_names` need:
    /// `bodies`, `system_history`, `atlas_city_names`.
    fn make_db(body_id: &str, system_id: &str, settlement_wave: Option<&str>) -> PathBuf {
        let n = SEQ.fetch_add(1, Ordering::Relaxed);
        let path = std::env::temp_dir().join(format!("sr_adp_{}_{n}.db", std::process::id()));
        let _ = std::fs::remove_file(&path);
        let conn = Connection::open(&path).expect("create db");
        conn.execute_batch(
            "CREATE TABLE bodies (body_id TEXT PRIMARY KEY, system_id TEXT NOT NULL);
             CREATE TABLE system_history (
                 system_id TEXT PRIMARY KEY,
                 settlement_wave TEXT
             );
             CREATE TABLE atlas_city_names (
                 id INTEGER PRIMARY KEY AUTOINCREMENT,
                 body_id TEXT NOT NULL,
                 name TEXT NOT NULL,
                 kind TEXT NOT NULL DEFAULT 'city'
             );",
        )
        .expect("create tables");
        conn.execute(
            "INSERT INTO bodies (body_id, system_id) VALUES (?1, ?2)",
            rusqlite::params![body_id, system_id],
        )
        .expect("insert body");
        if let Some(wave) = settlement_wave {
            conn.execute(
                "INSERT INTO system_history (system_id, settlement_wave) VALUES (?1, ?2)",
                rusqlite::params![system_id, wave],
            )
            .expect("insert system_history");
        }
        drop(conn);
        path
    }

    fn insert_city(db: &Path, body_id: &str, name: &str, kind: &str) {
        let conn = Connection::open(db).expect("reopen");
        conn.execute(
            "INSERT INTO atlas_city_names (body_id, name, kind) VALUES (?1, ?2, ?3)",
            rusqlite::params![body_id, name, kind],
        )
        .expect("insert city");
    }

    #[test]
    fn handle_city_names_request_no_reader_is_error() {
        let resp = handle_city_names_request(
            &CityNamesRequest {
                city_names: true,
                body_id: "GJ1c".into(),
            },
            None,
        );
        assert!(matches!(resp.status, CityNamesStatus::Error(_)));
        assert!(resp.cities.is_empty());
    }

    #[test]
    fn handle_city_names_request_sol_body_is_excluded() {
        // D-236: system_id = GJ-0 → SolExcluded, no DB row read for cities.
        let db = make_db("Earth", "GJ-0", None);
        insert_city(&db, "Earth", "London", "capital");
        let reader = CityContextReader::open(&db).expect("open");

        let resp = handle_city_names_request(
            &CityNamesRequest {
                city_names: true,
                body_id: "Earth".into(),
            },
            Some(&reader),
        );
        assert_eq!(resp.status, CityNamesStatus::SolExcluded);
        assert!(
            resp.cities.is_empty(),
            "Sol-excluded response must carry no cities even though the row exists"
        );
    }

    #[test]
    fn handle_city_names_request_sol_body_via_settlement_wave_is_excluded() {
        // D-236's second signal: settlement_wave = 'origin' excludes even a
        // non-GJ-0 system_id.
        let db = make_db("Weirdbody", "GJ-999", Some("origin"));
        let reader = CityContextReader::open(&db).expect("open");

        let resp = handle_city_names_request(
            &CityNamesRequest {
                city_names: true,
                body_id: "Weirdbody".into(),
            },
            Some(&reader),
        );
        assert_eq!(resp.status, CityNamesStatus::SolExcluded);
    }

    #[test]
    fn handle_city_names_request_ordinary_body_returns_names() {
        let db = make_db("GJ1c", "GJ-1", Some("first_wave"));
        insert_city(&db, "GJ1c", "Port Aldren", "capital");
        insert_city(&db, "GJ1c", "Millbrook", "city");
        let reader = CityContextReader::open(&db).expect("open");

        let resp = handle_city_names_request(
            &CityNamesRequest {
                city_names: true,
                body_id: "GJ1c".into(),
            },
            Some(&reader),
        );
        assert_eq!(resp.status, CityNamesStatus::Ready);
        assert_eq!(resp.cities.len(), 2);
        assert_eq!(resp.cities[0].name, "Port Aldren");
        assert!(resp.cities[0].is_capital);
        assert_eq!(resp.cities[1].name, "Millbrook");
        assert!(!resp.cities[1].is_capital);
    }

    #[test]
    fn handle_city_names_request_unknown_body_is_ready_with_empty_list() {
        // Matches read_body_settlements' existing convention: unknown body →
        // empty list under Ready, not a distinct NotFound status.
        let db = make_db("GJ1c", "GJ-1", Some("first_wave"));
        let reader = CityContextReader::open(&db).expect("open");

        let resp = handle_city_names_request(
            &CityNamesRequest {
                city_names: true,
                body_id: "ghost".into(),
            },
            Some(&reader),
        );
        assert_eq!(resp.status, CityNamesStatus::Ready);
        assert!(resp.cities.is_empty());
    }
}