"""Shared Blender helpers for the G2 strategic buildings of Champions of Luneraria.

Every G2 generator (Ancient, towers, boss grotto, Schlundkrone) builds its geometry from
these primitives, so the pieces share one design language: bevelled hard-surface stone and
metal, faceted crystals, rune bands with UVs for the glyph shader and rock masses from
noise-displaced spheres. After building, `finalize` sets split normals by angle and bakes an
ambient-occlusion term into the vertex colour `Col` (exported as COLOR_0); the Godot shaders
multiply it into stone and metal and use it for wear.

Material names (LN_*) are the contract with scripts/luneraria/view/lune_materials.gd; the
Blender colours only serve the .blend preview. Godot coordinates are written through
G(x, y, z) (x right, y up, z towards the viewer); Blender is Z-up.
"""
from pathlib import Path
import bpy, bmesh, json, hashlib, struct
from math import sin, cos, pi, sqrt, atan2
from mathutils import Vector, Matrix, noise
from mathutils.bvhtree import BVHTree

P = Path(__file__).resolve().parents[3]
SRC = Path(__file__).resolve().parent
OUT = P / 'assets/luneraria/g2'
V = Vector


def reset():
    _materials.clear()
    bpy.ops.wm.read_factory_settings(use_empty=True)
    bpy.context.preferences.filepaths.save_version = 0
    bpy.context.scene.render.fps = 30
    OUT.mkdir(parents=True, exist_ok=True)


def G(x, y, z):
    return V((x, -z, y))


def to_godot(v):
    return (v.x, v.z, -v.y)


def lin(c):
    return tuple(x ** 2.2 for x in c)


# Display colour (sRGB), roughness, metallic, emission strength.
PALETTE = {
    'LN_Stone_Pale': ((.80, .76, .68), .88, 0.0, 0.0),
    'LN_Stone_Dark': ((.26, .26, .29), .9, 0.0, 0.0),
    'LN_Stone_Grotto': ((.46, .43, .47), .92, 0.0, 0.0),
    'LN_Rock': ((.40, .39, .37), .95, 0.0, 0.0),
    'LN_Metal_Team': ((.74, .76, .80), .34, .9, 0.0),
    'LN_Metal_Iron': ((.22, .22, .24), .55, .8, 0.0),
    'LN_Metal_Bronze': ((.62, .44, .22), .42, .9, 0.0),
    'LN_Crystal_Team': ((.55, .80, 1.0), .08, 0.0, 3.0),
    'LN_Crystal_Grotto': ((.70, .50, 1.0), .08, 0.0, 3.0),
    'LN_Rune_Team': ((.55, .80, 1.0), .5, 0.0, 2.0),
    'LN_Rune_Grotto': ((.70, .50, 1.0), .5, 0.0, 2.0),
    'LN_Cloth_Team': ((.20, .40, .80), .85, 0.0, 0.0),
    'LN_Wood': ((.36, .25, .16), .8, 0.0, 0.0),
    'LN_Cave': ((.03, .02, .05), 1.0, 0.0, 0.0),
    'LN_Water_Glow': ((.45, .35, .80), .1, 0.0, 1.2),
    'LN_Boss_Hide': ((.24, .25, .29), .84, 0.0, 0.0),
    'LN_Boss_Bone': ((.80, .77, .69), .62, 0.0, 0.0),
    'LN_Boss_Bronze': ((.60, .44, .24), .42, .85, 0.0),
    'LN_Crystal_Boss': ((.70, .50, 1.0), .08, 0.0, 3.0),
}
_materials = {}


def material(name):
    if name in _materials:
        return _materials[name]
    color, rough, metal, emission = PALETTE[name]
    m = bpy.data.materials.new(name)
    c = lin(color)
    m.diffuse_color = (*c, 1)
    m.use_nodes = True
    nodes, links = m.node_tree.nodes, m.node_tree.links
    bsdf = nodes.get('Principled BSDF')
    bsdf.inputs['Roughness'].default_value = rough
    bsdf.inputs['Metallic'].default_value = metal
    # Baked occlusion (vertex colour Col) darkens the preview like it does in Godot.
    attribute = nodes.new('ShaderNodeVertexColor')
    attribute.layer_name = 'Col'
    mix = nodes.new('ShaderNodeMix')
    mix.data_type = 'RGBA'
    mix.blend_type = 'MULTIPLY'
    mix.inputs['Factor'].default_value = 1.0
    mix.inputs['A'].default_value = (*c, 1)
    links.new(attribute.outputs['Color'], mix.inputs['B'])
    links.new(mix.outputs['Result'], bsdf.inputs['Base Color'])
    if emission:
        bsdf.inputs['Emission Color'].default_value = (*c, 1)
        bsdf.inputs['Emission Strength'].default_value = emission
    _materials[name] = m
    return m


# ---------------------------------------------------------------- objects
def make(name, verts, faces, mat, uvs=None, smooth=False):
    """Object from Godot-space vertices (tuples or Vectors) and faces; uvs per vertex."""
    me = bpy.data.meshes.new(name)
    me.from_pydata([tuple(G(*v)) for v in verts], [], faces)
    me.update()
    me.materials.append(material(mat))
    if uvs is not None:
        layer = me.uv_layers.new(name='UVMap')
        for poly in me.polygons:
            for li in poly.loop_indices:
                layer.data[li].uv = uvs[me.loops[li].vertex_index]
    for poly in me.polygons:
        poly.use_smooth = smooth
    ob = bpy.data.objects.new(name, me)
    bpy.context.collection.objects.link(ob)
    return ob


def bevel(ob, offset=.03, segments=2, angle=35.0, profile=.5):
    """Bevels every edge sharper than `angle` degrees (hard-surface highlight edges)."""
    bm = bmesh.new()
    bm.from_mesh(ob.data)
    bmesh.ops.remove_doubles(bm, verts=list(bm.verts), dist=1e-6)
    bm.normal_update()
    limit = angle * pi / 180.0
    edges = [e for e in bm.edges if len(e.link_faces) == 2 and e.calc_face_angle(0.0) > limit]
    if edges:
        bmesh.ops.bevel(bm, geom=edges, offset=offset, offset_type='OFFSET', segments=segments, profile=profile,
                        affect='EDGES', clamp_overlap=True)
    bm.to_mesh(ob.data)
    bm.free()
    ob.data.update()
    return ob


def join(objects, name, origin=(0, 0, 0)):
    """Joins objects into one named object whose origin sits at the Godot point `origin`."""
    objects = [o for o in objects if o is not None]
    bpy.ops.object.select_all(action='DESELECT')
    for o in objects:
        o.select_set(True)
    bpy.context.view_layer.objects.active = objects[0]
    if len(objects) > 1:
        bpy.ops.object.join()
    ob = bpy.context.view_layer.objects.active
    ob.name = name
    ob.data.name = name
    pivot = G(*origin)
    ob.data.transform(Matrix.Translation(-pivot))
    ob.location = pivot
    return ob


# ---------------------------------------------------------------- primitives
def lathe(name, profile, sides, mat, center=(0, 0, 0), rotation=0.0, cap_top=True, cap_bottom=True, jitter=0.0, seed=0.0,
          smooth=False, uv_band=None):
    """Revolves a (radius, height) profile. uv_band=(cell_length) gives UVs u along the
    circumference in cells and v along the profile (0..1) for rune bands."""
    cx, cy, cz = center
    verts, faces, uvs = [], [], []
    n = len(profile)
    total = 0.0
    lengths = [0.0]
    for j in range(1, n):
        total += ((profile[j][0] - profile[j - 1][0]) ** 2 + (profile[j][1] - profile[j - 1][1]) ** 2) ** .5
        lengths.append(total)
    for j, (r, y) in enumerate(profile):
        for k in range(sides + (1 if uv_band else 0)):
            a = 2 * pi * (k % sides) / sides + rotation
            rr = r * (1 + jitter * noise.noise(V((cos(a) * 2.3, y * 1.7, sin(a) * 2.3 + seed)))) if jitter else r
            verts.append((cx + cos(a) * rr, cy + y, cz + sin(a) * rr))
            if uv_band:
                circumference = 2 * pi * max(r, .01)
                cells = max(1, round(circumference / uv_band))
                uvs.append((cells * k / sides, lengths[j] / max(total, 1e-6)))
    ring = sides + (1 if uv_band else 0)
    for j in range(n - 1):
        for k in range(sides):
            a0, b0 = j * ring + k, j * ring + (k + 1) % ring if not uv_band else j * ring + k + 1
            faces.append((a0, b0, b0 + ring, a0 + ring))
    if cap_bottom:
        faces.append(tuple(reversed(range(sides))))
    if cap_top:
        faces.append(tuple(range((n - 1) * ring, (n - 1) * ring + sides)))
    ob = make(name, verts, faces, mat, uvs if uv_band else None, smooth)
    # Faces must point outwards whatever the profile direction was.
    bm = bmesh.new()
    bm.from_mesh(ob.data)
    bmesh.ops.remove_doubles(bm, verts=list(bm.verts), dist=1e-6)
    bmesh.ops.recalc_face_normals(bm, faces=list(bm.faces))
    bm.to_mesh(ob.data)
    bm.free()
    return ob


def box(name, center, size, mat, yaw=0.0, pitch=0.0, roll=0.0, bev=.025, segments=1):
    hx, hy, hz = size[0] / 2, size[1] / 2, size[2] / 2
    rot = Matrix.Rotation(yaw, 3, 'Y') @ Matrix.Rotation(pitch, 3, 'X') @ Matrix.Rotation(roll, 3, 'Z')
    c = V(center)
    verts = []
    for dy in (-1, 1):
        for dz in (-1, 1):
            for dx in (-1, 1):
                verts.append(tuple(c + rot @ V((dx * hx, dy * hy, dz * hz))))
    faces = [(0, 1, 3, 2), (4, 6, 7, 5), (0, 4, 5, 1), (2, 3, 7, 6), (0, 2, 6, 4), (1, 5, 7, 3)]
    ob = make(name, verts, faces, mat)
    _outward(ob)
    if bev > 0:
        bevel(ob, bev, segments, 30.0)
    return ob


def _outward(ob):
    bm = bmesh.new()
    bm.from_mesh(ob.data)
    bmesh.ops.recalc_face_normals(bm, faces=list(bm.faces))
    bm.to_mesh(ob.data)
    bm.free()


def prism(name, outline, y0, y1, mat, bev=.02, segments=1, top_scale=1.0):
    """Extrudes a closed Godot-xz outline from y0 to y1 (top optionally scaled around its centre)."""
    n = len(outline)
    cx = sum(p[0] for p in outline) / n
    cz = sum(p[1] for p in outline) / n
    verts = [(x, y0, z) for x, z in outline]
    verts += [(cx + (x - cx) * top_scale, y1, cz + (z - cz) * top_scale) for x, z in outline]
    faces = [(i, (i + 1) % n, n + (i + 1) % n, n + i) for i in range(n)]
    faces += [tuple(reversed(range(n))), tuple(range(n, 2 * n))]
    ob = make(name, verts, faces, mat)
    _outward(ob)
    if bev > 0:
        bevel(ob, bev, segments, 30.0)
    return ob


def sweep(name, points, widths, thicknesses, mat, up_hint=(0, 1, 0), steps=24, lens=0.0, closed_ends=True, uv_cells=None,
          smooth=True, twist=0.0):
    """Sweeps a rectangle (optionally lens-shaped) along a Catmull-Rom path through Godot points.
    widths/thicknesses are sampled along the path. uv_cells gives rune UVs (u along, v across)."""
    pts = [V(p) for p in points]

    def cat(t):
        seg = min(len(pts) - 2, int(t * (len(pts) - 1)))
        u = t * (len(pts) - 1) - seg
        a, b, c, d = [pts[max(0, min(len(pts) - 1, q))] for q in (seg - 1, seg, seg + 1, seg + 2)]
        return .5 * ((2 * b) + (-a + c) * u + (2 * a - 5 * b + 4 * c - d) * u * u + (-a + 3 * b - 3 * c + d) * u * u * u)

    def sample(values, t):
        f = t * (len(values) - 1)
        i = min(len(values) - 2, int(f))
        return values[i] * (1 - (f - i)) + values[i + 1] * (f - i)

    # Rectangle corners with optional lens bulge: 8 points around the section.
    section = [(-1, -1), (0, -1 - lens), (1, -1), (1, 0), (1, 1), (0, 1 + lens), (-1, 1), (-1, 0)]
    verts, faces, uvs = [], [], []
    along = 0.0
    previous = None
    for j in range(steps + 1):
        t = j / steps
        p = cat(t)
        tangent = (cat(min(1, t + .01)) - cat(max(0, t - .01))).normalized()
        hint = V(up_hint)
        side = tangent.cross(hint)
        if side.length < 1e-4:
            side = tangent.cross(V((1, 0, 0)))
        side.normalize()
        normal = side.cross(tangent).normalized()
        if twist:
            ang = twist * t
            side, normal = side * cos(ang) + normal * sin(ang), normal * cos(ang) - side * sin(ang)
        if previous is not None:
            along += (p - previous).length
        previous = p
        w, th = sample(widths, t) * .5, sample(thicknesses, t) * .5
        for k, (sx, sy) in enumerate(section):
            verts.append(tuple(p + side * sx * w + normal * sy * th))
            uvs.append(((along / uv_cells) if uv_cells else t, k / 8.0))
        if j:
            base = (j - 1) * 8
            for k in range(8):
                a0, b0 = base + k, base + (k + 1) % 8
                faces.append((a0, b0, b0 + 8, a0 + 8))
    if closed_ends:
        faces.append(tuple(reversed(range(8))))
        faces.append(tuple(range(steps * 8, steps * 8 + 8)))
    ob = make(name, verts, faces, mat, uvs, smooth)
    _outward(ob)
    return ob


def crystal(name, center, radius, top, bottom, mat, sides=6, tilt=(0.0, 0.0), twist=0.0, seed=0, shoulder=.62):
    """Faceted crystal: a prism with a pointed crown and a shorter pointed foot. Facet radii
    vary slightly per side so the highlights break up."""
    c = V(center)
    rot = Matrix.Rotation(tilt[0], 3, 'X') @ Matrix.Rotation(tilt[1], 3, 'Z')
    verts = [tuple(c + rot @ V((0, top, 0)))]
    rings = [(shoulder * top, 1.0), (-shoulder * bottom * .5, 1.0)]
    for y, scale in rings:
        for k in range(sides):
            a = 2 * pi * k / sides + twist
            rr = radius * scale * (1 + .12 * noise.noise(V((k * 1.7, y, seed))))
            verts.append(tuple(c + rot @ V((cos(a) * rr, y, sin(a) * rr))))
    verts.append(tuple(c + rot @ V((0, -bottom, 0))))
    faces = [(0, 1 + (k + 1) % sides, 1 + k) for k in range(sides)]
    for k in range(sides):
        faces.append((1 + k, 1 + (k + 1) % sides, 1 + sides + (k + 1) % sides, 1 + sides + k))
    last = 1 + 2 * sides
    faces += [(last, 1 + sides + k, 1 + sides + (k + 1) % sides) for k in range(sides)]
    ob = make(name, verts, faces, mat)
    _outward(ob)
    return ob


def blob(name, center, radii, mat, seed=0.0, subdiv=3, amp=.25, flatten_below=None, yaw=0.0, crag=0.0):
    """Rock mass: icosphere displaced by fractal noise (and optional terraced crags)."""
    bm = bmesh.new()
    bmesh.ops.create_icosphere(bm, subdivisions=subdiv, radius=1.0)
    c = V(center)
    rot = Matrix.Rotation(yaw, 3, 'Y')
    for v in bm.verts:
        d = v.co.normalized()
        n = noise.fractal(d * 1.6 + V((seed, seed * .7, seed * .3)), 1.0, 2.0, 4)
        r = 1.0 + amp * n
        if crag:
            r += crag * abs(noise.noise(d * 3.1 + V((seed * 1.3, 0, 0))))
        p = V((d.x * radii[0] * r, d.y * radii[1] * r, d.z * radii[2] * r))
        if flatten_below is not None and p.y < flatten_below:
            p.y = flatten_below + (p.y - flatten_below) * .15
        v.co = G(*(c + rot @ p))
    me = bpy.data.meshes.new(name)
    bm.to_mesh(me)
    bm.free()
    me.materials.append(material(mat))
    ob = bpy.data.objects.new(name, me)
    bpy.context.collection.objects.link(ob)
    return ob


def chunk(name, center, size, mat, seed=0.0, yaw=0.0, tilt=0.0, sink=.25):
    """Broken masonry fragment: a low-poly displaced icosphere with a flat bed, irregular and
    angular (rubble, debris, ruins). `sink` buries the bottom into the ground."""
    bm = bmesh.new()
    bmesh.ops.create_icosphere(bm, subdivisions=1, radius=1.0)
    c = V(center)
    rot = Matrix.Rotation(yaw, 3, 'Y') @ Matrix.Rotation(tilt, 3, 'X')
    sx, sy, sz = size
    for v in bm.verts:
        d = v.co.normalized()
        r = 1.0 + .28 * noise.noise(d * 2.1 + V((seed, seed * 1.9, seed * .4)))
        p = V((d.x * sx * r, d.y * sy * r, d.z * sz * r))
        # Flatten faces into cut planes so fragments look split, not rounded.
        p.x = max(-sx * .82, min(sx * .82, p.x))
        p.z = max(-sz * .82, min(sz * .82, p.z))
        p.y = max(-sy * (1 - sink), min(sy * .9, p.y))
        v.co = G(*(c + rot @ p))
    me = bpy.data.meshes.new(name)
    bm.to_mesh(me)
    bm.free()
    me.materials.append(material(mat))
    ob = bpy.data.objects.new(name, me)
    bpy.context.collection.objects.link(ob)
    return ob


def cliff(name, center, radii, mat, seed=0.0, cuts=7, subdiv=2, amp=.16, yaw=0.0, lean=(0.0, 0.0), flat_bottom=None):
    """Faceted cliff rock in the low-poly language of the map rocks: a displaced icosphere cut
    by a few random planes (split faces), leaning optionally. Flat shading comes from
    finalize()'s angle split. flat_bottom (Godot y, absolute) flattens everything below it."""
    bm = bmesh.new()
    bmesh.ops.create_icosphere(bm, subdivisions=subdiv, radius=1.0)
    rng = seed * 7.31
    planes = []
    for k in range(cuts):
        # Cut normals biased sideways and up, so faces read as cleft rock, not as a gem.
        a = 2 * pi * ((k * .618 + seed * .17) % 1.0)
        tilt = .25 + .9 * ((k * .377 + seed * .29) % 1.0)
        n = V((cos(a) * sin(tilt * 1.2), cos(tilt * 1.2) * .6, sin(a) * sin(tilt * 1.2))).normalized()
        planes.append((n, .6 + .26 * ((k * .731 + rng) % 1.0)))
    c = V(center)
    rot = Matrix.Rotation(yaw, 3, 'Y') @ Matrix.Rotation(lean[0], 3, 'X') @ Matrix.Rotation(lean[1], 3, 'Z')
    for v in bm.verts:
        d = v.co.normalized()
        r = 1.0 + amp * noise.fractal(d * 1.9 + V((seed, seed * .7, seed * .3)), 1.0, 2.0, 3)
        q = d * r
        for n, off in planes:
            over = q.dot(n) - off
            if over > 0:
                q -= n * over
        p = V((q.x * radii[0], q.y * radii[1], q.z * radii[2]))
        w = c + rot @ p
        if flat_bottom is not None and w.y < flat_bottom:
            w.y = flat_bottom
        v.co = G(*w)
    me = bpy.data.meshes.new(name)
    bm.to_mesh(me)
    bm.free()
    me.materials.append(material(mat))
    ob = bpy.data.objects.new(name, me)
    bpy.context.collection.objects.link(ob)
    return ob


def ring(name, center, radius, width, thickness, mat, sides=48, axis_tilt=(0.0, 0.0), uv_cell=None, bev=.02):
    """Flat ring (rectangular section) around the Godot y axis, tilted by (x, z) angles.
    The outer band carries rune UVs when uv_cell is given."""
    c = V(center)
    rot = Matrix.Rotation(axis_tilt[0], 3, 'X') @ Matrix.Rotation(axis_tilt[1], 3, 'Z')
    section = [(radius - width / 2, -thickness / 2), (radius + width / 2, -thickness / 2),
               (radius + width / 2, thickness / 2), (radius - width / 2, thickness / 2)]
    verts, faces, uvs = [], [], []
    cells = max(1, round(2 * pi * radius / uv_cell)) if uv_cell else 1
    for k in range(sides + 1):
        a = 2 * pi * k / sides
        for s, (r, y) in enumerate(section):
            verts.append(tuple(c + rot @ V((cos(a) * r, y, sin(a) * r))))
            uvs.append((cells * k / sides, 0.0 if s in (0, 1) else 1.0))
    for k in range(sides):
        for s in range(4):
            a0, b0 = k * 4 + s, k * 4 + (s + 1) % 4
            faces.append((a0, b0, b0 + 4, a0 + 4))
    ob = make(name, verts, faces, mat, uvs)
    _outward(ob)
    if bev > 0:
        bevel(ob, bev, 1, 30.0)
    return ob


def band(name, center, radius, y0, y1, mat, sides=48, uv_cell=.35, inset=0.0):
    """Vertical cylindrical band (rune frieze) with UVs: u in glyph cells, v across."""
    c = V(center)
    verts, faces, uvs = [], [], []
    cells = max(1, round(2 * pi * radius / uv_cell))
    for k in range(sides + 1):
        a = 2 * pi * k / sides
        for s, y in enumerate((y0, y1)):
            verts.append((c.x + cos(a) * (radius + inset), c.y + y, c.z + sin(a) * (radius + inset)))
            uvs.append((cells * k / sides, float(s)))
    for k in range(sides):
        faces.append((k * 2, k * 2 + 2, k * 2 + 3, k * 2 + 1))
    ob = make(name, verts, faces, mat, uvs)
    _outward(ob)
    return ob


def panel(name, center, width, height, normal_yaw, mat, depth=.02, uv_cells=(1, 1)):
    """Thin rectangular inlay facing the Godot direction normal_yaw (for rune panels)."""
    c = V(center)
    right = V((cos(normal_yaw), 0, -sin(normal_yaw)))
    out = V((sin(normal_yaw), 0, cos(normal_yaw)))
    up = V((0, 1, 0))
    verts, uvs = [], []
    for sy in (-1, 1):
        for sx in (-1, 1):
            verts.append(tuple(c + right * sx * width / 2 + up * sy * height / 2 + out * depth))
            uvs.append(((sx + 1) / 2 * uv_cells[0], (sy + 1) / 2 * uv_cells[1]))
    faces = [(0, 1, 3, 2)]
    ob = make(name, verts, faces, mat, uvs)
    return ob


def disc_grid(name, center, radius, mat, rings=6, sides=48, y=0.0, uv_scale=None):
    """Flat disc (Godot y up) with polar UVs: u = angle cells, v = radius (for floor runes)."""
    c = V(center)
    verts, faces, uvs = [(c.x, c.y + y, c.z)], [], [(0.0, 0.0)]
    for j in range(1, rings + 1):
        r = radius * j / rings
        for k in range(sides + 1):
            a = 2 * pi * k / sides
            verts.append((c.x + cos(a) * r, c.y + y, c.z + sin(a) * r))
            uvs.append((k / sides * (uv_scale or 1.0), j / rings))
    for k in range(sides):
        faces.append((0, 1 + k + 1, 1 + k))
    ring_n = sides + 1
    for j in range(rings - 1):
        for k in range(sides):
            a0 = 1 + j * ring_n + k
            faces.append((a0, a0 + 1, a0 + 1 + ring_n, a0 + ring_n))
    ob = make(name, verts, faces, mat, uvs)
    for poly in ob.data.polygons:
        poly.use_smooth = True
    # Faces up.
    bm = bmesh.new()
    bm.from_mesh(ob.data)
    for f in bm.faces:
        f.normal_update()
        if f.normal.z < 0:
            f.normal_flip()
    bm.to_mesh(ob.data)
    bm.free()
    return ob


def banner(name, width, height, mat, shape='swallowtail', segments=(6, 12), top=(0, 0, 0), yaw=0.0):
    """Hanging cloth below the Godot point `top`: UV v runs 0 at the pole to 1 at the hem, so
    the cloth shader weights the wind by v. shape: 'swallowtail' (Team A, cool) or 'flame'
    (Team B, warm: three flame tongues)."""
    nx, ny = segments
    t = V(top)
    rot = Matrix.Rotation(yaw, 3, 'Y')
    verts, uvs, faces = [], [], []
    for j in range(ny + 1):
        v = j / ny
        for i in range(nx + 1):
            u = i / nx
            x = (u - .5) * width
            y = -v * height
            if j == ny:
                if shape == 'swallowtail':
                    y += height * .28 * (1 - abs(u - .5) * 2)
                else:
                    y -= height * .12 * max(0.0, cos((u - .5) * 3 * 2 * pi)) ** 2
            verts.append(tuple(t + rot @ V((x, y, 0))))
            uvs.append((u, v))
    for j in range(ny):
        for i in range(nx):
            a = j * (nx + 1) + i
            faces.append((a, a + 1, a + nx + 2, a + nx + 1))
    ob = make(name, verts, faces, mat, uvs, smooth=True)
    return ob


# ---------------------------------------------------------------- finishing
def finalize(objects, sharp_angle=40.0, ao=True, rays=24, reach=2.2, ground=0.0, occluders=None, seed=7):
    """Split normals by angle, then bake ambient occlusion into the vertex colour Col.
    Occlusion is traced against all `occluders` (default: the objects themselves) plus the
    ground plane at Godot height `ground`, so feet of walls and inner corners darken."""
    for ob in objects:
        me = ob.data
        bm = bmesh.new()
        bm.from_mesh(me)
        bmesh.ops.remove_doubles(bm, verts=list(bm.verts), dist=1e-6)
        bm.to_mesh(me)
        bm.free()
        me.shade_smooth()
        me.set_sharp_from_angle(angle=sharp_angle * pi / 180.0)
        me.update()
    if not ao:
        for ob in objects:
            _fill_color(ob, lambda i: 1.0)
        return
    sources = occluders if occluders is not None else objects
    verts, polys = [], []
    for ob in sources:
        mw = ob.matrix_world
        base = len(verts)
        verts += [mw @ v.co for v in ob.data.vertices]
        polys += [tuple(base + i for i in p.vertices) for p in ob.data.polygons]
    tree = BVHTree.FromPolygons(verts, polys, epsilon=0.0)
    # Fixed, well spread hemisphere directions (golden spiral), rotated per vertex.
    dirs = []
    for i in range(rays):
        z = 1 - (i + .5) / rays
        r = sqrt(max(0.0, 1 - z * z))
        a = i * 2.39996323
        dirs.append(V((cos(a) * r, sin(a) * r, z)))
    ground_z = ground  # Blender z == Godot y
    for ob in objects:
        mw = ob.matrix_world
        nm = mw.to_3x3().inverted().transposed()
        values = []
        for v in ob.data.vertices:
            p = mw @ v.co
            n = (nm @ v.normal).normalized()
            t = n.orthogonal().normalized()
            b = n.cross(t)
            hit = 0.0
            origin = p + n * .012
            for d in dirs:
                w = t * d.x + b * d.y + n * d.z
                blocked = False
                if w.z < -1e-4 and origin.z >= ground_z:
                    dist = (origin.z - ground_z) / -w.z
                    blocked = dist < reach
                if not blocked:
                    loc, _, _, dist = tree.ray_cast(origin, w, reach)
                    blocked = loc is not None
                if blocked:
                    hit += d.z
            weight = sum(d.z for d in dirs)
            values.append(max(0.0, 1.0 - hit / weight))
        _fill_color(ob, lambda i, values=values: .28 + .72 * values[i] ** .8)


def _fill_color(ob, fn):
    me = ob.data
    attr = me.color_attributes.get('Col') or me.color_attributes.new(name='Col', type='FLOAT_COLOR', domain='POINT')
    for i, item in enumerate(attr.data):
        a = fn(i)
        item.color = (a, a, a, 1.0)
    me.color_attributes.active_color = attr
    me.color_attributes.render_color_index = me.color_attributes.find('Col')


def triangulate(ob):
    bm = bmesh.new()
    bm.from_mesh(ob.data)
    bmesh.ops.triangulate(bm, faces=list(bm.faces))
    bm.to_mesh(ob.data)
    bm.free()


def triangles(objects):
    total = 0
    for ob in objects:
        total += sum(len(p.vertices) - 2 for p in ob.data.polygons)
    return total


def export(objects, glb_name, blend_name, extra_objects=()):
    """Saves the .blend and exports the given objects (plus armatures) as GLB. Returns the
    parsed glTF JSON and the raw bytes for the manifest."""
    bpy.ops.wm.save_as_mainfile(filepath=str(SRC / blend_name))
    bpy.ops.object.select_all(action='DESELECT')
    for ob in list(objects) + list(extra_objects):
        ob.select_set(True)
    bpy.context.view_layer.objects.active = objects[0]
    path = OUT / glb_name
    bpy.ops.export_scene.gltf(filepath=str(path), export_format='GLB', use_selection=True, export_materials='EXPORT',
                              export_yup=True, export_animations=False, export_vertex_color='ACTIVE', export_normals=True,
                              export_apply=False)
    raw = path.read_bytes()
    doc = json.loads(raw[20:20 + struct.unpack_from('<I', raw, 12)[0]])
    return doc, raw


def glb_triangles(doc):
    return sum(doc['accessors'][q['indices']]['count'] // 3 for m in doc['meshes'] for q in m['primitives'])


def bounds_godot(objects):
    lo = [1e9, 1e9, 1e9]
    hi = [-1e9, -1e9, -1e9]
    for ob in objects:
        for v in ob.data.vertices:
            g = to_godot(ob.matrix_world @ v.co)
            for i in range(3):
                lo[i] = min(lo[i], g[i])
                hi[i] = max(hi[i], g[i])
    return {'min': [round(x, 4) for x in lo], 'max': [round(x, 4) for x in hi]}


def record(asset_id, glb_name, blend_name, generator, objects, doc, raw, **extra):
    nodes = sorted(n.get('name', '') for n in doc.get('nodes', []))
    entry = {'id': asset_id, 'resource_path': 'res://assets/luneraria/g2/' + glb_name,
             'source': 'assets-source/luneraria/g2/' + blend_name, 'generator': 'assets-source/luneraria/g2/' + generator,
             'triangles': glb_triangles(doc), 'nodes': nodes, 'materials': sorted(m['name'] for m in doc.get('materials', [])),
             'bounds_godot': bounds_godot(objects), 'pivot': 'ground centre (0, 0, 0)', 'units': 'metres (Godot 1 unit = 1 m)',
             'sha256': hashlib.sha256(raw).hexdigest()}
    entry.update(extra)
    return entry


def write_manifest(entries):
    """Merges entries (by id) into assets/luneraria/g2/g2_manifest.json."""
    path = OUT / 'g2_manifest.json'
    data = json.loads(path.read_text()) if path.exists() else {'assets': []}
    by_id = {e['id']: e for e in data['assets']}
    for e in entries:
        by_id[e['id']] = e
    data['assets'] = [by_id[k] for k in sorted(by_id)]
    path.write_text(json.dumps(data, indent=2, ensure_ascii=False) + '\n')