"""
Dynamic Dimensioning and Scaled Metrics Engine for PDF Exporter.
Centralizes all auto-scaling calculations for grid steps, legend ticks, arrows,
line widths, font sizes, and SA2 technical measure offsets.
"""
import math
import numpy as np

MM_TO_PT = 2.834645669291339


def compute_grid_steps(w_geom: float, h_geom: float) -> tuple[float, float]:
    """
    Computes human-readable main_step (mm) and minor_step (mm) for grid overlay.
    """
    L = max(w_geom, h_geom)
    if L > 1e-6:
        step_raw = L / 10.0
        exponent = int(np.round(np.log10(step_raw)))
        main_step = 10.0 ** exponent
    else:
        main_step = 10.0
    minor_step = main_step / 10.0
    return main_step, minor_step


def compute_effective_stroke_and_font(
    line_width_mm: float,
    font_size_mm: float,
    minor_step_mm: float
) -> tuple[float, float]:
    """
    Calculates line_width_pt and font_size_pt proportionally based on minor_step_mm.
    Scales continuously from millimetric components up to large structural models.
    """
    if line_width_mm <= 0:
        line_width_pt = minor_step_mm * 0.05 * MM_TO_PT
    else:
        line_width_pt = line_width_mm * MM_TO_PT

    if font_size_mm <= 0:
        font_size_pt = minor_step_mm * MM_TO_PT
    else:
        font_size_pt = font_size_mm * MM_TO_PT

    return line_width_pt, font_size_pt


class LegendSizing:
    """
    Auto-scaling calculations for the Size Scale Legend (bottom-left grid scale bar).
    """
    def __init__(self, main_step_mm: float, minor_step_mm: float, line_width_pt: float, font_size_pt: float):
        self.main_step = main_step_mm
        self.minor_step = minor_step_mm

        self.line_width_pt = line_width_pt
        self.font_size_pt = font_size_pt

        # Tick heights in mm proportional to main grid step
        self.major_tick_mm = main_step_mm * 0.10
        self.minor_tick_mm = main_step_mm * 0.05

        # Y-axis height in mm (extends comfortably past major tick height)
        self.y_axis_height_mm = self.major_tick_mm * 2.0

        # X-axis extension past last main step tick in mm
        self.x_axis_extension_mm = minor_step_mm * 2.0

        # Legend Arrowhead dimensions in PT (proportional to line width)
        self.arrow_len_pt = max(0.5, line_width_pt * 12.0)
        self.arrow_half_w_pt = self.arrow_len_pt * 0.35

        self.label_margin_h_pt = self.minor_tick_mm * 1.0
        self.label_margin_w_pt = self.minor_tick_mm * 1.5


class SA2Sizing:
    """
    Auto-scaling calculations for SA2 technical measurement lines and feature callouts.
    """
    def __init__(self, w_obj_mm: float, h_obj_mm: float, line_width_pt: float, font_size_pt: float):
        self.w_obj = w_obj_mm
        self.h_obj = h_obj_mm
        self.line_width_pt = line_width_pt
        self.font_size_pt = font_size_pt

        self.obj_ref_size = min(w_obj_mm, h_obj_mm) if min(w_obj_mm, h_obj_mm) > 0 else max(w_obj_mm, h_obj_mm)

        # Dimension line offset & extension line scaling (mm) proportional to object size
        self.offset_mm = self.obj_ref_size * 0.10
        self.ext_overhang_mm = self.offset_mm * 0.20
        self.ext_gap_mm = self.offset_mm * 0.10

        # Measure arrow dimensions (PT)
        self.arrow_len_pt = max(0.5, line_width_pt * 4.0)
        self.arrow_half_w_pt = self.arrow_len_pt * 0.35

    def get_hole_callout_lengths(self, dia_mm: float) -> tuple[float, float]:
        slant_mm = dia_mm * 0.30
        leader_mm = dia_mm * 0.40
        return slant_mm, leader_mm

    def get_arc_callout_lengths(self, r_mm: float) -> tuple[float, float]:
        slant_mm = r_mm * 0.30
        leader_mm = r_mm * 0.40
        return slant_mm, leader_mm

    def get_chamfer_callout_lengths(self, c_val_mm: float) -> tuple[float, float]:
        slant_mm = c_val_mm * 1.0
        leader_mm = c_val_mm * 1.5
        return slant_mm, leader_mm