#!/usr/bin/env python3
"""Generate every LLeMbas SVG asset from one source of truth.

Why a generator rather than five hand-written files: the leaf mark appears in
the icon, the favicon, the lockup and the banner. Keeping the geometry in one
place is the only way those stay identical as the mark is tuned.

Why the wordmark is outlines and not <text>: a README banner on GitHub or Gitea
cannot load a webfont, so <text> would render in whatever serif the viewer
happens to have. Outlines look the same everywhere. Letterforms come from
Source Serif 4 (Adobe, SIL OFL 1.1); only the handful of glyphs actually used
are extracted, as a static drawing -- no font binary is redistributed.

This is a design-time tool. The application never imports it, and the generated
files are committed. Re-run it only when the artwork itself changes:

    pip install fonttools cairosvg
    python scripts/build_artwork.py

cairosvg is needed only for the PWA icons, which have to be PNG: an installed
web app's icon is drawn by the operating system's launcher, and neither
Android's adaptive-icon masking nor iOS's home screen will take an SVG. The
rasterisation happens here, once, and the PNGs are committed like everything
else -- the running application still has no build step and no rasteriser.
"""

from __future__ import annotations

import argparse
import random
import sys
from pathlib import Path

try:
    from fontTools.pens.boundsPen import BoundsPen
    from fontTools.pens.svgPathPen import SVGPathPen
    from fontTools.pens.transformPen import TransformPen
    from fontTools.ttLib import TTFont
except ImportError:  # pragma: no cover - design-time tool
    sys.exit("fontTools is required for this script: pip install fonttools")

ROOT = Path(__file__).resolve().parent.parent
ASSETS = ROOT / "assets"
STATIC_IMG = ROOT / "src" / "lembas" / "web" / "static" / "img"

# assets/ holds the design masters; the application serves its own copies from
# static/. These are the few the running app actually needs.
SERVED_BY_APP = (
    "favicon.svg",
    "logo-mark.svg",
    "banner.svg",
    "icon-192.png",
    "icon-512.png",
    "icon-maskable-512.png",
    "apple-touch-icon-180.png",
)

FONT_SEMIBOLD = Path("/usr/share/fonts/adobe-source-serif/SourceSerif4Display-Semibold.otf")
FONT_ITALIC = Path("/usr/share/fonts/adobe-source-serif/SourceSerif4Display-It.otf")

WORDMARK = "LLeMbas"
TAGLINE = "Waybread for the long road of thought"
# The capitals of LLeMbas spell LLM. Those three glyphs carry the accent colour.
ACCENT_GLYPHS = frozenset({0, 1, 3})

# --- Palette -----------------------------------------------------------------
GOLD_LIGHT = "#EACB74"
GOLD = "#C9A227"
GOLD_DARK = "#916F13"
GOLD_SCORE = "#7A5C10"
GOLD_HILIGHT = "#F6E3A8"
RUNE_GOLD = "#E0B252"

LEAF_EDGE = "#93A5B6"
LEAF_LIGHT = "#F1F6FA"
LEAF_MID = "#B8C7D5"
LEAF_VEIN = "#61758A"
LEAF_STEM = "#8A9AA8"

NIGHT_TOP = "#080B0F"
NIGHT_MID = "#101822"
NIGHT_LOW = "#1A2530"
PARCHMENT = "#EDE6D6"
INK = "#1B1F23"
MUTED = "#9AA7B4"

# --- The mallorn leaf --------------------------------------------------------
# Drawn once, in a 64x64 box, and reused everywhere. Tuned so the silhouette
# still reads as a leaf at 16px, where veins and score lines disappear.
LEAF_BLADE = (
    "M20.5 45.5 C13.8 31.7 23.8 20.9 45.5 18.5 C49.8 35 39.8 45.8 20.5 45.5 Z"
)
LEAF_MIDRIB = "M20.5 45.5 C28 38 36 29 45.5 18.5"
LEAF_STEM_PATH = "M21.2 44.8 L17 49.4"
LEAF_VEINS = [
    "M26.9 38.8 Q25.2 35.8 24.9 32.1",
    "M32.3 33.1 Q30.9 30.3 30.4 26.9",
    "M37.8 27.0 Q36.6 24.6 36.3 21.7",
    "M26.9 38.8 Q30.5 40.1 33.7 40.3",
    "M32.3 33.1 Q35.8 34.3 38.6 34.5",
    "M37.8 27.0 Q40.8 27.9 43.2 28.1",
]

HEADER = '<svg xmlns="http://www.w3.org/2000/svg"'


# --- Type --------------------------------------------------------------------
class TextRun:
    """A string converted to SVG outlines, positioned with the baseline at y=0."""

    def __init__(self, font_path: Path, text: str, cap_px: float):
        if not font_path.exists():
            sys.exit(f"font not found: {font_path}")
        font = TTFont(font_path)
        cmap = font.getBestCmap()
        glyph_set = font.getGlyphSet()
        hmtx = font["hmtx"]
        # Scale to cap height rather than em size: it is what the eye measures.
        cap_height = getattr(font["OS/2"], "sCapHeight", None) or font["head"].unitsPerEm * 0.7
        scale = cap_px / cap_height

        self.glyphs: list[dict] = []
        pen_x = 0.0
        x0 = y0 = float("inf")
        x1 = y1 = float("-inf")

        for index, char in enumerate(text):
            if char == " ":
                pen_x += hmtx[cmap[ord(" ")]][0] * scale
                continue
            name = cmap.get(ord(char))
            if name is None:
                sys.exit(f"{font_path.name} has no glyph for {char!r}")

            # Font coordinates run upwards; SVG's run downwards, hence -scale.
            transform = (scale, 0, 0, -scale, pen_x, 0)
            svg_pen = SVGPathPen(glyph_set, ntos=lambda v: f"{v:.2f}")
            glyph_set[name].draw(TransformPen(svg_pen, transform))
            bounds_pen = BoundsPen(glyph_set)
            glyph_set[name].draw(TransformPen(bounds_pen, transform))

            if bounds_pen.bounds:
                gx0, gy0, gx1, gy1 = bounds_pen.bounds
                x0, y0 = min(x0, gx0), min(y0, gy0)
                x1, y1 = max(x1, gx1), max(y1, gy1)

            self.glyphs.append(
                {"char": char, "index": index, "path": svg_pen.getCommands()}
            )
            pen_x += hmtx[name][0] * scale

        self.x0, self.y0, self.x1, self.y1 = x0, y0, x1, y1
        self.width = x1 - x0
        self.height = y1 - y0

    def paths(
        self,
        accent_indices: frozenset[int] = frozenset(),
        *,
        indent: str = "  ",
        base_class: str = "base",
        accent_class: str = "accent",
    ) -> str:
        """Render the glyphs, offset so the run's left edge sits at x=0.

        Class names are caller-supplied because <style> inside an SVG is scoped
        to the whole document, not to the group it sits in. Two runs in one file
        sharing a class name means the second rule silently recolours the first.
        """
        out = []
        for glyph in self.glyphs:
            cls = accent_class if glyph["index"] in accent_indices else base_class
            out.append(
                f'{indent}<path class="{cls}" data-char="{glyph["char"]}" '
                f'd="{glyph["path"]}"/>'
            )
        return "\n".join(out)

    @property
    def origin_shift(self) -> str:
        """Transform placing the run's top-left at the current origin."""
        return f"translate({-self.x0:.2f} {-self.y0:.2f})"


def type_style(indent: str = "    ") -> str:
    """Colour rules for outlined type.

    The CSS variables let the application theme the type when the SVG is
    inlined into a page. The literal fallbacks matter just as much: opened as a
    standalone file or loaded through <img>, no page CSS reaches the document,
    so the media query is the only thing keeping the wordmark legible on a dark
    background.
    """
    return f"""{indent}<style>
{indent}  .base {{ fill: var(--lembas-ink, {INK}); }}
{indent}  .accent {{ fill: var(--lembas-gold, {GOLD}); }}
{indent}  @media (prefers-color-scheme: dark) {{
{indent}    .base {{ fill: var(--lembas-ink, {PARCHMENT}); }}
{indent}    .accent {{ fill: var(--lembas-gold, {RUNE_GOLD}); }}
{indent}  }}
{indent}</style>"""


# --- The mark ----------------------------------------------------------------
def mark_defs(prefix: str) -> str:
    return f"""  <defs>
    <linearGradient id="{prefix}-wafer" x1="0" y1="0" x2="0.3" y2="1">
      <stop offset="0" stop-color="{GOLD_LIGHT}"/>
      <stop offset="0.5" stop-color="{GOLD}"/>
      <stop offset="1" stop-color="{GOLD_DARK}"/>
    </linearGradient>
    <linearGradient id="{prefix}-leaf" x1="0.1" y1="1" x2="0.9" y2="0">
      <stop offset="0" stop-color="{LEAF_EDGE}"/>
      <stop offset="0.4" stop-color="{LEAF_LIGHT}"/>
      <stop offset="1" stop-color="{LEAF_MID}"/>
    </linearGradient>
    <clipPath id="{prefix}-clip">
      <rect x="6" y="6" width="52" height="52" rx="13"/>
    </clipPath>
  </defs>"""


def mark_body(prefix: str, *, detail: bool = True) -> str:
    """The wafer-and-leaf mark in a 64x64 box.

    detail=False drops the score lines, rim and veins for small-size use.
    """
    parts = [f'  <rect x="6" y="6" width="52" height="52" rx="13" fill="url(#{prefix}-wafer)"/>']

    if detail:
        parts.append(f"""  <g clip-path="url(#{prefix}-clip)" fill="none" stroke-linecap="round">
    <g stroke="{GOLD_SCORE}" stroke-opacity="0.38" stroke-width="2">
      <path d="M32 6 V58"/>
      <path d="M6 32 H58"/>
    </g>
    <g stroke="{GOLD_HILIGHT}" stroke-opacity="0.3" stroke-width="1">
      <path d="M33.2 6 V58"/>
      <path d="M6 33.2 H58"/>
    </g>
  </g>
  <rect x="7.1" y="7.1" width="49.8" height="49.8" rx="11.9"
        fill="none" stroke="{GOLD_SCORE}" stroke-opacity="0.3" stroke-width="1.2"/>""")

    parts.append(f"""  <g>
    <path d="{LEAF_STEM_PATH}" stroke="{LEAF_STEM}" stroke-width="3"
          stroke-linecap="round" fill="none"/>
    <path d="{LEAF_BLADE}" fill="url(#{prefix}-leaf)"/>
    <path d="{LEAF_MIDRIB}" fill="none" stroke="{LEAF_VEIN}" stroke-opacity="0.5"
          stroke-width="1.5" stroke-linecap="round"/>""")

    if detail:
        veins = "\n".join(f'      <path d="{v}"/>' for v in LEAF_VEINS)
        parts.append(f"""    <g fill="none" stroke="{LEAF_VEIN}" stroke-opacity="0.32"
       stroke-width="1" stroke-linecap="round">
{veins}
    </g>""")

    parts.append("  </g>")
    return "\n".join(parts)


# --- Asset builders ----------------------------------------------------------
def build_logo_mark() -> str:
    return f"""{HEADER} viewBox="0 0 64 64" width="64" height="64"
     role="img" aria-label="LLeMbas">
  <title>LLeMbas</title>
  <desc>A silver mallorn leaf laid across a scored golden lembas wafer.</desc>
{mark_defs("m")}
{mark_body("m")}
</svg>
"""


def build_favicon() -> str:
    """Small-size variant: no score lines or veins, larger blade, tighter tile."""
    return f"""{HEADER} viewBox="0 0 64 64" width="64" height="64"
     role="img" aria-label="LLeMbas">
  <title>LLeMbas</title>
{mark_defs("f")}
  <rect x="2" y="2" width="60" height="60" rx="14" fill="url(#f-wafer)"/>
  <g transform="translate(32 32) scale(1.16) translate(-32 -32)">
    <path d="M20.6 44.6 L15.6 50.1" stroke="{LEAF_STEM}" stroke-width="3.4"
          stroke-linecap="round" fill="none"/>
    <path d="{LEAF_BLADE}" fill="url(#f-leaf)"/>
    <path d="{LEAF_MIDRIB}" fill="none" stroke="{LEAF_VEIN}" stroke-opacity="0.45"
          stroke-width="1.8" stroke-linecap="round"/>
  </g>
</svg>
"""


def build_wordmark() -> str:
    """Standalone type. Inherits colour so it can sit on any background."""
    run = TextRun(FONT_SEMIBOLD, WORDMARK, 100)
    return f"""{HEADER} viewBox="0 0 {run.width:.2f} {run.height:.2f}"
     width="{run.width:.2f}" height="{run.height:.2f}" role="img" aria-label="LLeMbas">
  <title>LLeMbas</title>
  <!-- Source Serif 4 (SIL OFL 1.1) outlines. The capitals L, L and M spell out
       LLM and take the accent colour; see scripts/build_artwork.py. -->
{type_style("  ")}
  <g transform="{run.origin_shift}">
{run.paths(ACCENT_GLYPHS, indent="    ")}
  </g>
</svg>
"""


def build_lockup() -> str:
    """Horizontal mark + wordmark, for the application header."""
    cap = 46.0
    run = TextRun(FONT_SEMIBOLD, WORDMARK, cap)
    mark_size = 64.0
    gap = 20.0
    pad = 4.0

    height = mark_size + pad * 2
    text_x = pad + mark_size + gap
    # Optically centre on the cap height rather than the full glyph bounds, so
    # the ascender of "b" and the overshoot of "e" do not shift the baseline.
    baseline_y = height / 2 + cap / 2
    width = text_x + run.width + pad

    return f"""{HEADER} viewBox="0 0 {width:.2f} {height:.2f}"
     width="{width:.2f}" height="{height:.2f}" role="img" aria-label="LLeMbas">
  <title>LLeMbas</title>
{mark_defs("l")}
{type_style("  ")}
  <g transform="translate({pad} {pad})">
{mark_body("l")}
  </g>
  <g transform="translate({text_x - run.x0:.2f} {baseline_y:.2f})">
{run.paths(ACCENT_GLYPHS, indent="    ")}
  </g>
</svg>
"""


# --- PWA icons ---------------------------------------------------------------
# Same geometry as everything else, rasterised because a launcher icon has to
# be a bitmap. Two shapes are needed, not one:
#
#   "any"      -- drawn as supplied, so the wafer's own rounded square is the
#                 silhouette and the corners stay transparent.
#   "maskable" -- Android crops it to a circle, squircle or rounded square of
#                 the launcher's choosing, so the art must be full-bleed and
#                 the mark must sit inside the central safe zone. An "any"
#                 icon used as maskable gets its corners sliced off.
#
# The Apple icon is opaque for a different reason: iOS composites a home screen
# icon onto black, so transparency reads as a black tile rather than as the
# wallpaper showing through.
def _framed_mark(prefix: str, *, background: str | None = None, inset: float = 0.0) -> str:
    """The mark on a 64x64 canvas, optionally opaque and inset from the edges."""
    size = 64.0
    offset = size * inset
    scale = 1.0 - inset * 2
    plate = f'  <rect width="{size:.0f}" height="{size:.0f}" fill="{background}"/>\n'
    return f"""{HEADER} viewBox="0 0 64 64" width="64" height="64"
     role="img" aria-label="LLeMbas">
{mark_defs(prefix)}
{plate if background else ""}  <g transform="translate({offset:.3f} {offset:.3f}) \
scale({scale:.4f})">
{mark_body(prefix)}
  </g>
</svg>
"""


def _rasterise(svg: str, size: int) -> bytes:
    try:
        import cairosvg
    except ImportError:  # pragma: no cover - design-time tool
        sys.exit("cairosvg is required for the PWA icons: pip install cairosvg")
    return cairosvg.svg2png(
        bytestring=svg.encode("utf-8"), output_width=size, output_height=size
    )


def build_icon_192() -> bytes:
    return _rasterise(_framed_mark("i192"), 192)


def build_icon_512() -> bytes:
    return _rasterise(_framed_mark("i512"), 512)


def build_icon_maskable() -> bytes:
    # 20% inset leaves the mark inside the central 60%, comfortably within the
    # 80% safe circle every launcher mask respects.
    return _rasterise(_framed_mark("imask", background=NIGHT_MID, inset=0.20), 512)


def build_apple_touch_icon() -> bytes:
    # iOS rounds the corners itself, so only a hairline of padding is wanted.
    return _rasterise(_framed_mark("iios", background=NIGHT_MID, inset=0.06), 180)


def _mountains(width: float, base_y: float, seed: int, height: float, colour: str) -> str:
    """One jagged ridge line spanning the full width."""
    rng = random.Random(seed)
    points = [(0.0, base_y)]
    x = 0.0
    while x < width:
        step = rng.uniform(width * 0.045, width * 0.11)
        x = min(x + step, width)
        peak = base_y - rng.uniform(height * 0.35, height)
        points.append((x, peak))
        # A short shoulder after each peak keeps the ridge from looking like a saw.
        if x < width:
            x = min(x + rng.uniform(width * 0.01, width * 0.03), width)
            points.append((x, peak + rng.uniform(height * 0.08, height * 0.25)))
    points.append((width, base_y))
    coords = " ".join(f"{px:.1f},{py:.1f}" for px, py in points)
    return f'  <polygon points="{coords} {width:.0f},999 0,999" fill="{colour}"/>'


def _stars(width: float, height: float, count: int, seed: int) -> str:
    rng = random.Random(seed)
    out = []
    for _ in range(count):
        sx = rng.uniform(0, width)
        sy = rng.uniform(0, height)
        r = rng.uniform(0.6, 1.9)
        opacity = rng.uniform(0.18, 0.85)
        out.append(
            f'    <circle cx="{sx:.1f}" cy="{sy:.1f}" r="{r:.2f}" opacity="{opacity:.2f}"/>'
        )
    return "\n".join(out)


def _drifting_leaves(seed: int) -> str:
    """A few mallorn leaves adrift in the sky, well behind the type."""
    rng = random.Random(seed)
    placements = [
        (120, 90, 0.42, -18), (250, 250, 0.30, 24), (1035, 95, 0.36, 12),
        (1160, 215, 0.46, -32), (905, 300, 0.26, 40), (185, 300, 0.24, -8),
    ]
    out = []
    for cx, cy, scale, rot in placements:
        opacity = rng.uniform(0.10, 0.19)
        out.append(
            f'    <g transform="translate({cx} {cy}) rotate({rot}) '
            f'scale({scale}) translate(-32 -32)" opacity="{opacity:.2f}">'
            f'<path d="{LEAF_BLADE}" fill="{RUNE_GOLD}"/></g>'
        )
    return "\n".join(out)


def build_banner() -> str:
    """README hero.

    Carries its own dark background rather than relying on the page, because a
    README is rendered on a light background as often as a dark one.
    """
    width, height = 1280.0, 420.0
    cap = 92.0
    run = TextRun(FONT_SEMIBOLD, WORDMARK, cap)
    tag = TextRun(FONT_ITALIC, TAGLINE, 26.0)

    mark_size = 136.0
    gap = 34.0
    lockup_w = mark_size + gap + run.width
    lockup_x = (width - lockup_w) / 2
    baseline_y = 232.0
    mark_y = baseline_y - cap / 2 - mark_size / 2

    tag_x = (width - tag.width) / 2 - tag.x0
    tag_y = baseline_y + 68.0

    mark_scale = mark_size / 64.0

    return f"""{HEADER} viewBox="0 0 {width:.0f} {height:.0f}"
     width="{width:.0f}" height="{height:.0f}" role="img"
     aria-label="LLeMbas - {TAGLINE}">
  <title>LLeMbas</title>
  <desc>{TAGLINE}. A mallorn leaf and wafer above the mountains at night.</desc>
  <defs>
    <linearGradient id="b-sky" x1="0" y1="0" x2="0" y2="1">
      <stop offset="0" stop-color="{NIGHT_TOP}"/>
      <stop offset="0.62" stop-color="{NIGHT_MID}"/>
      <stop offset="1" stop-color="{NIGHT_LOW}"/>
    </linearGradient>
    <radialGradient id="b-glow" cx="0.5" cy="0.54" r="0.5">
      <stop offset="0" stop-color="{GOLD}" stop-opacity="0.22"/>
      <stop offset="1" stop-color="{GOLD}" stop-opacity="0"/>
    </radialGradient>
    <!-- Cool light sitting just above the ridge line, so the far mountains
         separate from the near ones instead of merging into one dark mass. -->
    <radialGradient id="b-horizon" cx="0.5" cy="1" r="0.72">
      <stop offset="0" stop-color="#4E6C86" stop-opacity="0.30"/>
      <stop offset="1" stop-color="#4E6C86" stop-opacity="0"/>
    </radialGradient>
{mark_defs("b").removeprefix("  <defs>").removesuffix("  </defs>").rstrip()}
  </defs>

  <rect width="{width:.0f}" height="{height:.0f}" fill="url(#b-sky)"/>
  <g fill="#FFFFFF">
{_stars(width, 300, 130, 11)}
  </g>
  <rect y="180" width="{width:.0f}" height="240" fill="url(#b-horizon)"/>
  <rect width="{width:.0f}" height="{height:.0f}" fill="url(#b-glow)"/>
{_drifting_leaves(5)}

  <!-- Ridge lines, furthest first. Each is lighter than the one in front of it,
       which is what reads as distance. -->
{_mountains(width, 366, 3, 150, "#1C2836")}
{_mountains(width, 392, 8, 112, "#111A25")}
{_mountains(width, 416, 21, 74, "#080D13")}
  <rect y="{height - 5:.0f}" width="{width:.0f}" height="5" fill="{GOLD}" opacity="0.55"/>

  <!-- Lockup. Colours are fixed rather than themed: the banner carries its own
       night sky, so it must not follow the reader's colour scheme. -->
  <g transform="translate({lockup_x:.2f} {mark_y:.2f}) scale({mark_scale:.4f})">
{mark_body("b")}
  </g>
  <g transform="translate({lockup_x + mark_size + gap - run.x0:.2f} {baseline_y:.2f})">
    <style>.base {{ fill: {PARCHMENT}; }} .accent {{ fill: {RUNE_GOLD}; }}</style>
{run.paths(ACCENT_GLYPHS, indent="    ")}
  </g>
  <g transform="translate({tag_x:.2f} {tag_y:.2f})">
    <style>.tag {{ fill: {MUTED}; }}</style>
{tag.paths(indent="    ", base_class="tag")}
  </g>
</svg>
"""


# --- Entry point -------------------------------------------------------------
BUILDERS = {
    "logo-mark.svg": build_logo_mark,
    "favicon.svg": build_favicon,
    "wordmark.svg": build_wordmark,
    "logo-lockup.svg": build_lockup,
    "banner.svg": build_banner,
    "icon-192.png": build_icon_192,
    "icon-512.png": build_icon_512,
    "icon-maskable-512.png": build_icon_maskable,
    "apple-touch-icon-180.png": build_apple_touch_icon,
}


def main() -> None:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--out", type=Path, default=ASSETS)
    parser.add_argument("--only", nargs="*", choices=sorted(BUILDERS), default=None)
    args = parser.parse_args()

    args.out.mkdir(parents=True, exist_ok=True)
    STATIC_IMG.mkdir(parents=True, exist_ok=True)

    for filename in args.only or BUILDERS:
        content = BUILDERS[filename]()
        # The PNG builders return bytes; everything else returns SVG source.
        data = content if isinstance(content, bytes) else content.encode("utf-8")

        path = args.out / filename
        path.write_bytes(data)
        print(f"wrote {path.relative_to(ROOT)} ({len(data):,} bytes)")

        if filename in SERVED_BY_APP:
            served = STATIC_IMG / filename
            served.write_bytes(data)
            print(f"      -> {served.relative_to(ROOT)}")


if __name__ == "__main__":
    main()