from __future__ import annotations
import math
from typing import Any


def parse_gcode_preview_geometry(
    gcode: str,
    scale_factor: float = 0.001,
    scale_length: float = 1.0,
    show_e_0: bool = False,
) -> dict[str, Any]:
    """
    Parses G-code text and extracts vertices, edges, and e_rates for mesh preview generation.
    Returns a dict with:
        vertices: list[tuple[float, float, float]]
        edges: list[tuple[int, int]]
        e_rates: list[float]
        default_layer_height: float
        prep_translation: list[float]
        prep_rotation: list[float]
        prep_scale: list[float]
    """
    vertices: list[tuple[float, float, float]] = []
    edges: list[tuple[int, int]] = []
    e_rates: list[float] = []

    last_x, last_y, last_z = 0.0, 0.0, 0.0
    last_e = 0.0

    offset_x, offset_y = 0.0, 0.0
    custom_default_extrusion_rate = 0.0
    default_layer_height = 0.2
    default_layer_width = 0.4

    last_v_idx = -1
    last_p2 = None

    prep_translation = [0.0, 0.0, 0.0]
    prep_rotation = [0.0, 0.0, 0.0]
    prep_scale = [1.0, 1.0, 1.0]

    for line in gcode.splitlines():
        # Parse metadata from comments
        if ';' in line:
            comment = line.split(';', 1)[1].strip()
            if comment.startswith("OFFSET_X="):
                try: offset_x = float(comment.split('=')[1])
                except ValueError: pass
            elif comment.startswith("OFFSET_Y="):
                try: offset_y = float(comment.split('=')[1])
                except ValueError: pass
            elif comment.startswith("DEFAULT_EXTRUSION_RATE="):
                try: custom_default_extrusion_rate = float(comment.split('=')[1])
                except ValueError: pass
            elif comment.startswith("DEFAULT_LAYER_HEIGHT="):
                try: default_layer_height = float(comment.split('=')[1])
                except ValueError: pass
            elif comment.startswith("DEFAULT_LAYER_WIDTH="):
                try: default_layer_width = float(comment.split('=')[1])
                except ValueError: pass
            elif comment.startswith("PREPARATION_TOTAL_TRANSLATION="):
                try:
                    vals = [float(v) for v in comment.split('=')[1].split(',')]
                    if len(vals) >= 3: prep_translation = vals[:3]
                except ValueError: pass
            elif comment.startswith("PREPARATION_TOTAL_ROTATION="):
                try:
                    vals = [float(v) for v in comment.split('=')[1].split(',')]
                    if len(vals) >= 3: prep_rotation = vals[:3]
                except ValueError: pass
            elif comment.startswith("PREPARATION_TOTAL_SCALE="):
                try:
                    vals = [float(v) for v in comment.split('=')[1].split(',')]
                    if len(vals) >= 3: prep_scale = vals[:3]
                except ValueError: pass

        line_no_comment = line.split(';')[0].strip()
        if not line_no_comment: continue

        parts = line_no_comment.split()
        if not parts: continue
        cmd = parts[0].upper()

        params = {}
        for p in parts[1:]:
            if len(p) < 2: continue
            try:
                val = float(p[1:])
                if p[0].upper() in 'XYZ':
                    val *= scale_factor
                params[p[0].upper()] = val
            except ValueError: continue

        new_x = params.get('X', last_x)
        new_y = params.get('Y', last_y)
        new_z = params.get('Z', last_z)
        new_e = params.get('E', last_e)

        show = False
        if show_e_0: show = True
        if cmd == 'G1' and new_e > 0: show = True

        if show:
            ox, oy = offset_x * scale_factor, offset_y * scale_factor
            p1 = (last_x - ox, last_y - oy, last_z)
            p2 = (new_x - ox, new_y - oy, new_z)

            seg_len_mm = math.dist(p1, p2) * (1000.0 * scale_length)
            if seg_len_mm > 0 and custom_default_extrusion_rate > 0:
                e_rate = (new_e / seg_len_mm) / custom_default_extrusion_rate
            else:
                e_rate = 1.0

            if last_v_idx != -1 and p1 == last_p2:
                v2_idx = len(vertices)
                vertices.append(p2)
                edges.append((last_v_idx, v2_idx))
                last_v_idx = v2_idx
            else:
                v1_idx = len(vertices)
                v2_idx = v1_idx + 1
                vertices.extend([p1, p2])
                edges.append((v1_idx, v2_idx))
                last_v_idx = v2_idx

            e_rates.append(e_rate)
            last_p2 = p2
        else:
            last_v_idx = -1
            last_p2 = None

        last_x, last_y, last_z = new_x, new_y, new_z
        last_e = new_e

    return {
        "vertices": vertices,
        "edges": edges,
        "e_rates": e_rates,
        "default_layer_height": default_layer_height,
        "prep_translation": prep_translation,
        "prep_rotation": prep_rotation,
        "prep_scale": prep_scale,
    }