"""
Venus (GJ0c) terrain builder.

Data source:
  - Elevation: Magellan radar altimetry from USGS Astrogeology
    Global topography at ~4.6 km/px, PDS format.

Venus properties:
  - Surface: volcanic, extremely hot (~735K), dense CO2 atmosphere
  - No liquid water, thick clouds
  - Min elevation: ~-2000 m (lowlands)
  - Max elevation: ~11000 m (Maxwell Montes on Ishtar Terra)
  - planet_class: "volcanic", atmosphere: "toxic"
"""

import numpy as np
from pathlib import Path

from sol_data.download import ensure_cached
from sol_data.shared import (
    GRID_W, GRID_H,
    load_tiff_as_array, load_raw_binary, resample_to_grid, normalize_01,
    compute_hillshade, assemble_terrain,
    temperature_grid_analytical,
)

# Magellan topography — USGS GeoTIFF (reliable, PIL-loadable)
MAGELLAN_TIFF_URL = "https://planetarymaps.usgs.gov/mosaic/Venus_Magellan_Topography_Global_4641m_v02.tif"
MAGELLAN_TIFF_FILE = "Venus_Magellan_Topography_Global_4641m_v02.tif"

# PDS fallback (raw binary, dimensions may vary)
MAGELLAN_PDS_URL = "https://pds-geosciences.wustl.edu/mgn/mgn-v-rdrs-5-dim-v1/mg_3002/gedr/gtdr/gtdr_shtplt.img"
MAGELLAN_PDS_FILE = "venus_magellan_gtdr.img"

VENUS_MIN_ELEV_M = -2000.0
VENUS_MAX_ELEV_M = 11000.0
VENUS_SURFACE_TEMP_K = 735.0  # nearly uniform due to dense atmosphere


def _load_magellan() -> np.ndarray:
    """Load Magellan topography data."""
    # Try USGS GeoTIFF first (reliable, well-defined format)
    try:
        path = ensure_cached(MAGELLAN_TIFF_URL, MAGELLAN_TIFF_FILE)
        print(f"    loading Magellan GeoTIFF: {path}")
        arr = load_tiff_as_array(str(path))
        # Handle nodata
        arr[arr < -20000] = 0.0
        arr[arr > 20000] = 0.0
        print(f"    Magellan shape: {arr.shape}, "
              f"range: [{arr.min():.0f}, {arr.max():.0f}] m")
        return arr
    except Exception as e:
        print(f"    GeoTIFF failed ({e}), trying PDS binary...")

    # PDS fallback — try common dimension/format combinations
    try:
        path = ensure_cached(MAGELLAN_PDS_URL, MAGELLAN_PDS_FILE)
        print(f"    loading Magellan PDS: {path}")
        for w, h in [(4096, 2048), (2048, 1024), (8192, 4096)]:
            try:
                arr = load_raw_binary(str(path), w, h, dtype=">i2", offset=0)
                arr[arr > 20000] = 0.0
                arr[arr < -20000] = 0.0
                print(f"    Magellan PDS: {w}x{h}, range: [{arr.min():.0f}, {arr.max():.0f}]")
                return arr
            except ValueError:
                continue
    except Exception as e3:
        print(f"    PDS also failed ({e3})")

    # All sources failed — fall through to procedural generation
    print("    WARNING: all Magellan sources failed, using procedural")
    return None


def build_terrain(body_def: dict) -> dict:
    """Build Venus terrain dict from Magellan data."""
    import sys
    sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
    from planet_simulation import compute_biome

    print("  Venus: loading Magellan data...")

    # ── 1. Elevation ────────────────────────────────────────────────────
    raw = _load_magellan()
    if raw is None:
        # Fall back to procedural simulation
        import sys
        sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
        from planet_simulation import simulate
        return simulate(body_def)

    from sol_data.shared import greenwich_to_dateline
    shifted = greenwich_to_dateline(raw)
    elevation_m = resample_to_grid(shifted, GRID_H, GRID_W, order=1)
    elevation = normalize_01(elevation_m, VENUS_MIN_ELEV_M, VENUS_MAX_ELEV_M)

    sea_level = 0.0
    surface_water = np.zeros((GRID_H, GRID_W), dtype=bool)

    # ── 2. Temperature ──────────────────────────────────────────────────
    # Venus has nearly uniform surface temperature due to dense atmosphere
    temperature_K = temperature_grid_analytical(
        base_T_K=VENUS_SURFACE_TEMP_K,
        elevation=elevation,
        lapse_rate_K_per_unit=50.0,  # slight cooling at altitude
        lat_gradient_K=5.0,          # almost no lat variation (thick atmo)
    )

    # ── 3. Moisture ─────────────────────────────────────────────────────
    moisture = np.zeros((GRID_H, GRID_W), dtype=np.float32)

    # ── 4. Biome ────────────────────────────────────────────────────────
    biome = compute_biome(body_def, elevation, sea_level, surface_water,
                          temperature_K, moisture)

    # ── 5. Hillshade ────────────────────────────────────────────────────
    hillshade = compute_hillshade(elevation)

    return assemble_terrain(
        elevation=elevation, temperature_K=temperature_K,
        moisture=moisture, biome=biome,
        surface_water=surface_water, hillshade=hillshade,
        rivers=[], sea_level=sea_level,
    )