import base64
import math
import pathlib
from flask import Flask, render_template, request, Response
from html import escape
from fontTools.ttLib import TTFont
from fontTools.pens.svgPathPen import SVGPathPen

app = Flask(__name__)

VERSION = "0.75"

_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>'
)

_FONT_OBJ  = TTFont(str(_FONT_PATH))
_GLYPH_SET = _FONT_OBJ.getGlyphSet()
_CMAP      = _FONT_OBJ.getBestCmap()
_HMTX      = _FONT_OBJ['hmtx'].metrics
_UPM       = _FONT_OBJ['head'].unitsPerEm

# SVG absolute coordinate constants (1 user unit = 1 mm)
ZERO_X    = 60.844130
MAX_X     = 180.251230
BAR_Y     = 107.54670
SCALE_LEN = MAX_X - ZERO_X   # 119.4071 mm

BIG_H   = 5.0895
SMALL_H = 2.6683

_UNIT_AREA_WIDTH = 18.445
_UNIT_SCALE_X    = 0.96486402
_UNIT_CHAR_EM    = 0.65


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:
    # Snap near-integers — log-scale geometric values accumulate FP error
    # (e.g. 9999.9999), which would otherwise miss the integer case.
    r = round(v)
    if abs(v - r) < 1e-9 * max(1.0, abs(v)):
        return str(int(r))
    # 4 significant figures in fixed-point notation (never scientific).
    exp = math.floor(math.log10(abs(v)))
    decimals = max(0, 4 - 1 - exp)
    s = f"{v:.{decimals}f}"
    return s.rstrip('0').rstrip('.') if '.' in s else s


def _text_to_paths(text, x, y, font_size, anchor='start', fill='#1a1a1a', wrap_transform=None):
    s = font_size / _UPM

    if anchor == 'middle':
        total_w = sum(
            _HMTX.get(_CMAP.get(ord(ch)), (0, 0))[0] * s
            for ch in text if _CMAP.get(ord(ch))
        )
        x -= total_w / 2

    parts = []
    cx = x
    for ch in text:
        gn = _CMAP.get(ord(ch))
        if gn is None:
            continue
        pen = SVGPathPen(_GLYPH_SET)
        _GLYPH_SET[gn].draw(pen)
        d = pen.getCommands()
        if d:
            t = f'translate({cx:.5f},{y:.5f}) scale({s:.8f},{-s:.8f})'
            parts.append(f'<path style="fill:{fill}" transform="{t}" d="{d}"/>')
        cx += _HMTX.get(gn, (0, 0))[0] * s

    inner = '\n'.join(parts)
    if wrap_transform:
        return f'<g transform="{wrap_transform}">{inner}</g>'
    return inner


def generate_svg(unit, min_val, max_val, range_label, big_ticks, small_ticks, label_count,
                 use_paths=True, log_scale=False, custom_labels=None):
    if log_scale:
        if min_val <= 0 or max_val <= 0:
            raise ValueError("Logarithmic scale requires min and max values greater than 0.")
        lmin, lmax = math.log(min_val), math.log(max_val)
        lspan = lmax - lmin
        if lspan == 0:
            raise ValueError("Logarithmic scale requires min and max values to differ.")

        def value_to_x(v):
            return ZERO_X + SCALE_LEN * (math.log(v) - lmin) / lspan

        def major_value(i):
            return min_val * (max_val / min_val) ** (i / big_ticks)
    else:
        span = max_val - min_val

        def value_to_x(v):
            if span == 0:
                return ZERO_X
            return ZERO_X + SCALE_LEN * (v - min_val) / span

        def major_value(i):
            return min_val + (max_val - min_val) * i / big_ticks

    big_interval = SCALE_LEN / big_ticks
    # Major ticks are always physically evenly spaced; only their values differ.
    big_xs = [ZERO_X + i * big_interval for i in range(big_ticks + 1)]
    big_vals = [major_value(i) for i in range(big_ticks + 1)]

    # Custom labels, when supplied, override the calculated numbers and set the count.
    if custom_labels:
        label_count = max(1, min(len(custom_labels), big_ticks + 1))
        custom_labels = custom_labels[:label_count]
    else:
        label_count = max(2, min(label_count, big_ticks + 1))

    if label_count == 1:
        label_indices = [0]
    else:
        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">',
    ]

    if use_paths:
        parts.append('  <g transform="translate(-37.352226,-90.454928)">')
    else:
        parts += [_FONT_FACE, '  <g transform="translate(-37.352226,-90.454928)">']

    parts.append(
        '    <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" />'
    )

    if use_paths:
        parts += [
            '    ' + _text_to_paths(
                unit, 41.455711, 109.03796, _unit_font_size(unit),
                wrap_transform=f'scale({_UNIT_SCALE_X},1.0364155)'
            ),
            '    ' + _text_to_paths(range_label, 184.79707, 113.6755, 3.60539),
        ]
    else:
        fs = _unit_font_size(unit)
        parts += [
            f'    <text style="font-size:{fs:.4f}px;font-family:\'ГОСТ тип А\',monospace;fill:#1a1a1a"'
            f' x="41.455711" y="109.03796"'
            f' transform="scale({_UNIT_SCALE_X},1.0364155)">{escape(unit)}</text>',
            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 — evenly spaced in value, then positioned by the scale mapping.
    # On a linear scale this is uniform; on a log scale they crowd toward the high end.
    if small_ticks > 0:
        sub = small_ticks + 1
        for i in range(big_ticks):
            for j in range(1, small_ticks + 1):
                v = big_vals[i] + j * (big_vals[i + 1] - big_vals[i]) / sub
                x = value_to_x(v)
                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
    for k, idx in enumerate(label_indices):
        x = big_xs[idx]
        label = custom_labels[k] if custom_labels else _fmt(big_vals[idx])
        if use_paths:
            parts.append('    ' + _text_to_paths(label, x, 101.49598, 8.89194, anchor='middle'))
        else:
            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(label)}</text>'
            )

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


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


@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)))
    use_paths   = request.form.get('output_mode', 'paths') == 'paths'
    log_scale   = request.form.get('scale_type', 'linear') == 'log'

    custom_labels = [s.strip() for s in request.form.get('labels', '').split(',') if s.strip()] or None

    try:
        svg = generate_svg(unit, min_val, max_val, range_label, big_ticks, small_ticks,
                           label_count, use_paths, log_scale, custom_labels)
    except ValueError as err:
        return Response(str(err), status=400, mimetype='text/plain')
    return Response(svg, mimetype='image/svg+xml')


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