import hashlib
import math

from shapely.geometry import Point, Polygon

DISTRICT_RANGES = {
    "Downtown": (20.0, 60.0),
    "Ocean Beach": (8.0, 25.0),
    "default": (6.0, 15.0),
}
LANDMARK_SNAP = 20.0      # Meter: so weit darf ein Wahrzeichenpunkt vom Grundriss entfernt liegen


def _seeded_unit(seed: int, key: str) -> float:
    digest = hashlib.sha256(f"{seed}:{key}".encode()).digest()
    return int.from_bytes(digest[:8], "big") / 2 ** 64


def assign_heights(polys: list[Polygon], landmarks: list[dict],
                   districts: list[dict], seed: int) -> list[dict]:
    out = []
    for poly in polys:
        centroid = poly.centroid
        key = f"{centroid.x:.1f},{centroid.y:.1f}"
        hit = None
        for lm in landmarks:
            p = Point(lm["xyz"][0], lm["xyz"][1])
            if poly.contains(p) or poly.distance(p) <= LANDMARK_SNAP:
                if hit is None or lm["height"] > hit["height"]:
                    hit = lm
        if hit is not None:
            out.append({"height": float(hit["height"]), "source": "skyline"})
            continue
        name = "default"
        best = math.inf
        for d in districts:
            dist = math.dist((centroid.x, centroid.y), (d["x"], d["y"]))
            if dist < best:
                best, name = dist, d["name"] if d["name"] in DISTRICT_RANGES else "default"
        lo, hi = DISTRICT_RANGES[name]
        # Kleine Grundrisse bleiben niedriger: Fläche skaliert den oberen Rand.
        area_factor = min(1.0, poly.area / 400.0)
        height = lo + (hi - lo) * _seeded_unit(seed, key) * (0.4 + 0.6 * area_factor)
        out.append({"height": round(height, 1), "source": "district"})
    return out


PALM_SPACING = 12.0        # Meter entlang der Mittellinie
PALM_BEACH_RANGE = 40.0    # Meter Abstand zur nächsten Sandfläche
PALM_CLEARANCE = 6.0       # Meter Abstand zu Gebäuden
PALM_KERB = 1.5            # Meter Abstand zum Fahrbahnrand
# Versatzkandidaten von innen nach außen; genommen wird der erste, der Fahrbahn und
# Gebäude freihält. Ein fester Wert geht nicht: die Fahrbahn ist an den Mittellinien-
# punkten p50 5,4 m, p90 11,7 m, p95 14,0 m halbbreit (am echten Mosaik gemessen).
PALM_VERGE = (6.0, 8.0, 10.0, 12.0, 14.0, 16.0)


def _verge_point(line, p, side: str, roads, buildings, land):
    """Erster Versatz von innen nach außen, der Fahrbahn und Gebäude freihält und
    auf Land bleibt (Ruling 26: sonst schiebt der Versatz Küstenpalmen ins Wasser)."""
    for dist in PALM_VERGE:
        off = line.parallel_offset(dist, side)
        if off.is_empty:
            continue
        q = off.interpolate(off.project(p))
        if roads is not None and q.distance(roads) < PALM_KERB:
            continue
        if buildings is not None and q.distance(buildings) < PALM_CLEARANCE:
            continue
        if land is not None and not land.contains(q):
            continue
        return [(round(q.x, 2), round(q.y, 2))]
    return []


def palm_points(sand_polys, park_polys, road_lines, building_polys, road_polys,
                 land_polys, seed: int):
    """Palmen entlang strandnaher Mittellinien und verstreut in Parks."""
    from shapely.ops import unary_union
    sand = unary_union(sand_polys) if sand_polys else None
    roads = unary_union(list(road_polys)) if road_polys else None
    buildings = unary_union(list(building_polys)) if building_polys else None
    land = unary_union(land_polys) if land_polys else None
    blocked = unary_union([g for g in (roads, buildings) if g is not None]) \
        if (roads is not None or buildings is not None) else None
    points = []
    for line in road_lines:
        if sand is None or line.distance(sand) > PALM_BEACH_RANGE:
            continue
        # Start bei halber Teilung: die Mittellinien sind an Kreuzungen getrennt, ein
        # Start bei 0 setzt je Ast eine Palme in denselben Punkt.
        pos = min(PALM_SPACING / 2, line.length / 2)
        while pos <= line.length:
            p = line.interpolate(pos)
            for side in ("left", "right"):
                points.extend(_verge_point(line, p, side, roads, buildings, land))
            pos += PALM_SPACING
    for park in park_polys:
        minx, miny, maxx, maxy = park.bounds
        n = int(park.area // 250)
        for k in range(n):
            u = _seeded_unit(seed, f"park:{minx:.0f}:{k}:x")
            v = _seeded_unit(seed, f"park:{miny:.0f}:{k}:y")
            q = Point(minx + u * (maxx - minx), miny + v * (maxy - miny))
            if park.contains(q) and (blocked is None or q.distance(blocked) > PALM_CLEARANCE):
                points.append((round(q.x, 2), round(q.y, 2)))
    return list(dict.fromkeys(points))