//! Aircraft performance profile, loaded from `data/aircraft/<icao>.json`.

use std::path::Path;

use serde::{Deserialize, Serialize};

use crate::error::{CoreError, Result};
use crate::perf::openap::PerfModel;

/// Per-phase speeds and fuel flow plus regulatory reserves for one aircraft type.
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub struct AircraftProfile {
    pub icao: String,
    pub name: String,
    pub default_cruise_fl: i32,
    pub phases: Phases,
    pub reserves: Reserves,
    /// Optional physics-based (OpenAP) coefficients. When present, fuel flow is
    /// computed from drag at the actual mass/altitude instead of the fixed
    /// per-phase `fuel_flow_kgph` figures.
    #[serde(default)]
    pub openap: Option<OpenApParams>,
}

/// OpenAP-derived aerodynamic and engine coefficients plus mass envelope.
#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub struct OpenApParams {
    pub wing_area_m2: f64,
    pub cd0: f64,
    pub induced_k: f64,
    pub n_engines: u32,
    pub engine: String,
    pub max_thrust_n: f64,
    pub tsfc_cruise_g_per_ns: f64,
    pub ff_idle_kgs: f64,
    pub ref_cruise_alt_ft: f64,
    pub oew_kg: f64,
    pub mtow_kg: f64,
    pub mlw_kg: f64,
    pub max_fuel_kg: f64,
    pub cruise_mach: f64,
}

impl OpenApParams {
    /// Build the runtime physics model from these coefficients.
    pub fn model(&self) -> PerfModel {
        PerfModel {
            wing_area_m2: self.wing_area_m2,
            cd0: self.cd0,
            induced_k: self.induced_k,
            n_engines: self.n_engines,
            max_thrust_n: self.max_thrust_n,
            tsfc_cruise_g_per_ns: self.tsfc_cruise_g_per_ns,
            ff_idle_kgs: self.ff_idle_kgs,
            ref_cruise_alt_ft: self.ref_cruise_alt_ft,
        }
    }

    /// Default payload (kg) when the caller gives none: 70 % of a max-payload
    /// proxy (MLW − OEW). A stand-in until real max-zero-fuel-weight data is
    /// added; yields a realistic ~medium load factor.
    pub fn default_payload_kg(&self) -> f64 {
        0.70 * (self.mlw_kg - self.oew_kg)
    }
}

#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub struct Phases {
    pub climb: ClimbPhase,
    pub cruise: CruisePhase,
    pub descent: DescentPhase,
}

#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub struct ClimbPhase {
    pub ias_kt: f64,
    pub mach: f64,
    pub tas_kt: f64,
    pub fuel_flow_kgph: f64,
    pub roc_fpm: f64,
}

#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub struct CruisePhase {
    pub mach: f64,
    pub tas_kt: f64,
    pub fuel_flow_kgph: f64,
}

#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub struct DescentPhase {
    pub ias_kt: f64,
    pub mach: f64,
    pub tas_kt: f64,
    pub fuel_flow_kgph: f64,
    pub rod_fpm: f64,
}

#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
pub struct Reserves {
    pub final_reserve_min: f64,
    pub contingency_pct: f64,
    pub taxi_kg: f64,
}

impl AircraftProfile {
    /// Deserialize a profile from a JSON string.
    pub fn from_json_str(json: &str) -> Result<Self> {
        Ok(serde_json::from_str(json)?)
    }

    /// Load `<dir>/<icao lowercased>.json`.
    pub fn load(dir: &Path, icao: &str) -> Result<Self> {
        let path = dir.join(format!("{}.json", icao.to_lowercase()));
        let json = std::fs::read_to_string(&path).map_err(|e| {
            if e.kind() == std::io::ErrorKind::NotFound {
                CoreError::NotFound(format!("aircraft profile '{icao}' ({})", path.display()))
            } else {
                CoreError::Io(e)
            }
        })?;
        Self::from_json_str(&json)
    }
}

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

    #[test]
    fn loads_bundled_a320_profile() {
        // data/aircraft lives at the workspace root, two levels up from this crate.
        let dir = Path::new(env!("CARGO_MANIFEST_DIR")).join("../../data/aircraft");
        let p = AircraftProfile::load(&dir, "A320").unwrap();
        assert_eq!(p.icao, "A320");
        assert_eq!(p.default_cruise_fl, 360);
        assert!(p.phases.cruise.tas_kt > 400.0);
        assert_eq!(p.reserves.final_reserve_min, 30.0);
    }

    #[test]
    fn missing_profile_is_not_found() {
        let dir = Path::new(env!("CARGO_MANIFEST_DIR")).join("../../data/aircraft");
        let err = AircraftProfile::load(&dir, "ZZZZ").unwrap_err();
        assert!(err.to_string().contains("ZZZZ"), "{err}");
    }
}