import base64
import pathlib
from flask import Flask, render_template, request, Response
from html import escape

app = Flask(__name__)

_LOGO_PATH = pathlib.Path(__file__).parent / 'static' / 'logo.png'
_LOGO_B64 = base64.b64encode(_LOGO_PATH.read_bytes()).decode()

_FONT_PATH = pathlib.Path('/usr/local/share/fonts/г/ГОСТ_тип_А.ttf')
_FONT_B64 = base64.b64encode(_FONT_PATH.read_bytes()).decode()
_FONT_FACE = (
    '<defs><style>'
    '@font-face {'
    'font-family:"ГОСТ тип А";'
    f'src:url("data:font/truetype;base64,{_FONT_B64}") format("truetype");'
    '}'
    '</style></defs>'
)

# SVG absolute coordinate constants (1 user unit = 1 mm)
ZERO_X = 60.844130   # x of the zero/left tick
MAX_X = 180.251230   # x of the full-scale/right tick
BAR_Y = 107.54670    # y at the top of the scale bar (tick baseline)
SCALE_LEN = MAX_X - ZERO_X  # 119.4071 mm

BIG_H = 5.0895    # major tick height
SMALL_H = 2.6683  # minor tick height


_UNIT_AREA_WIDTH = 18.445  # canvas mm available for the unit label
_UNIT_SCALE_X = 0.96486402
_UNIT_CHAR_EM = 0.65       # approximate advance-width ratio for GOST typ A


def _unit_font_size(unit: str) -> float:
    n = max(1, len(unit))
    return min(18.7981, _UNIT_AREA_WIDTH / (n * _UNIT_SCALE_X * _UNIT_CHAR_EM))


def _fmt(v: float) -> str:
    if v == int(v):
        return str(int(v))
    return f"{v:.4g}"


def generate_svg(unit, min_val, max_val, range_label, big_ticks, small_ticks, label_count):
    big_interval = SCALE_LEN / big_ticks
    big_xs = [ZERO_X + i * big_interval for i in range(big_ticks + 1)]

    label_count = max(2, min(label_count, big_ticks + 1))
    label_indices = [round(k * big_ticks / (label_count - 1)) for k in range(label_count)]

    parts = [
        '<?xml version="1.0" encoding="UTF-8" standalone="no"?>',
        '<svg width="157.18373mm" height="26.683672mm"'
        ' viewBox="0 0 157.18373 26.683672" version="1.1"'
        ' xmlns="http://www.w3.org/2000/svg">',
        _FONT_FACE,
        '  <g transform="translate(-37.352226,-90.454928)">',

        # Background rect with scale-bar cutout
        '    <path style="fill:#ffffff;stroke:#1a1a1a;stroke-width:0.184;'
        'stroke-linecap:round;stroke-miterlimit:10"'
        ' d="M 37.444226,90.546928 V 117.0466 H 194.44395 V 90.546928 Z'
        ' M 58.443978,107.54692 H 183.64409 v 6.19963 H 58.443978 Z" />',

        # Unit label (large letter in left panel)
        f'    <text style="font-size:{_unit_font_size(unit):.4f}px;font-family:\'ГОСТ тип А\',monospace;fill:#1a1a1a"'
        f' x="41.455711" y="109.03796"'
        f' transform="scale(0.96486402,1.0364155)">{escape(unit)}</text>',

        # Range label inside the strip on the right
        f'    <text style="font-size:3.60539px;font-family:\'ГОСТ тип А\',monospace;fill:#1a1a1a"'
        f' x="184.79707" y="113.6755">{escape(range_label)}</text>',
    ]

    # Major ticks
    for x in big_xs:
        parts.append(
            f'    <line x1="{x:.5f}" y1="{BAR_Y}" x2="{x:.5f}" y2="{BAR_Y - BIG_H:.5f}"'
            f' style="stroke:#1a1a1a;stroke-width:0.555;stroke-linecap:butt" />'
        )

    # Minor ticks
    if small_ticks > 0:
        sub = small_ticks + 1
        for i in range(big_ticks):
            for j in range(1, small_ticks + 1):
                x = big_xs[i] + j * big_interval / sub
                parts.append(
                    f'    <line x1="{x:.5f}" y1="{BAR_Y}" x2="{x:.5f}" y2="{BAR_Y - SMALL_H:.5f}"'
                    f' style="stroke:#1a1a1a;stroke-width:0.302;stroke-linecap:butt" />'
                )

    # Numeric labels (centered on their tick, above the tick area)
    for idx in label_indices:
        x = big_xs[idx]
        val = min_val + (max_val - min_val) * idx / big_ticks
        parts.append(
            f'    <text style="font-size:8.89194px;font-family:\'ГОСТ тип А\',monospace;fill:#1a1a1a"'
            f' text-anchor="middle" x="{x:.5f}" y="101.49598">{escape(_fmt(val))}</text>'
        )

    parts += ['  </g>', '</svg>']
    return '\n'.join(parts)


@app.route('/')
def index():
    return render_template('index.html', logo_b64=_LOGO_B64)


@app.route('/generate', methods=['POST'])
def generate():
    unit = request.form.get('unit', '%')
    min_val = float(request.form.get('min', 0))
    max_val = float(request.form.get('max', 100))
    range_label = request.form.get('range_label', '5mA')
    big_ticks = max(1, min(50, int(request.form.get('big_ticks', 10))))
    small_ticks = max(0, min(20, int(request.form.get('small_ticks', 4))))
    label_count = max(2, int(request.form.get('label_count', 6)))

    svg = generate_svg(unit, min_val, max_val, range_label, big_ticks, small_ticks, label_count)
    return Response(svg, mimetype='image/svg+xml')


if __name__ == '__main__':
    app.run(debug=True)