#!/usr/bin/env python3
"""Write common/lib/wordmarkMetrics.ts: the advance of each Latin character
Archivo maps, at the wordmark's two instances (wdth 118; wght 720 for the lead,
380 for the suffix), measured from the vendored variable font
(umtool/report-to-video/fonts/Archivo[wdth,wght].ttf, the same bytes the video
lockup is outlined from).

The export header reserves the wordmark's width from this table
(common/lib/wordmarkWidth.ts), so whether a title fits beside the header's
icons is decided by the display face's widths, before and after the web font
loads: the fallback face is narrower, and a title that fitted in it would
otherwise show and then vanish when Archivo arrived.

  python3 common/bin/gen-wordmark-metrics.py            # rewrite the module
  python3 common/bin/gen-wordmark-metrics.py --stdout   # print it

Needs fontTools (pip install fonttools). The module records the fontTools
version it was generated with.
"""
import hashlib
import json
import os
import sys

import fontTools
from fontTools.ttLib import TTFont
from fontTools.varLib import instancer

HERE = os.path.dirname(os.path.abspath(__file__))
REPO = os.path.normpath(os.path.join(HERE, "..", ".."))
FONT = "Archivo[wdth,wght].ttf"
FONT_PATH = os.path.join(REPO, "umtool", "report-to-video", "fonts", FONT)
OUT = os.path.join(REPO, "common", "lib", "wordmarkMetrics.ts")
WEIGHTS = (720, 380)
WDTH = 118
# Basic Latin, Latin-1 and Latin Extended-A: what a site's title is written in.
WANT = [cp for a, b in ((32, 126), (160, 383)) for cp in range(a, b + 1)]


def runs(cps):
    out = []
    for cp in cps:
        if out and cp == out[-1][1] + 1:
            out[-1][1] = cp
        else:
            out.append([cp, cp])
    return out


def wrap(values, indent="      ", width=100):
    lines, line = [], ""
    for v in values:
        s = f"{v},"
        if line and len(indent) + len(line) + 1 + len(s) > width:
            lines.append(indent + line)
            line = s
        else:
            line = f"{line} {s}" if line else s
    if line:
        lines.append(indent + line)
    return "\n".join(lines)


def build():
    raw = open(FONT_PATH, "rb").read()
    sha = hashlib.sha256(raw).hexdigest()
    base = TTFont(FONT_PATH)
    upm = base["head"].unitsPerEm
    mapped = base.getBestCmap()
    cps = [cp for cp in WANT if cp in mapped]
    adv = {}
    for w in WEIGHTS:
        inst = instancer.instantiateVariableFont(TTFont(FONT_PATH), {"wght": w, "wdth": WDTH})
        cmap = inst.getBestCmap()
        hmtx = inst["hmtx"].metrics
        adv[w] = [hmtx[cmap[cp]][0] for cp in cps]
    parts = [
        "// GENERATED by common/bin/gen-wordmark-metrics.py -- do not edit; re-run it.",
        "//",
        f"// The advance, in font units, of each Latin character {FONT} maps, at the",
        f"// wordmark's instances (wdth {WDTH}; wght {' and '.join(map(str, WEIGHTS))}):",
        "// what lib/wordmarkWidth.ts reserves a title's width by.",
        "export const WORDMARK_METRICS = {",
        f"  font: {json.dumps(FONT)},",
        f"  sha256: {json.dumps(sha)},",
        f"  fontTools: {json.dumps(fontTools.version)},",
        f"  unitsPerEm: {upm},",
        f"  wdth: {WDTH},",
        "  // [first, last] codepoint ranges; the advances below follow them in order.",
        "  ranges: [",
        wrap([f"[{a}, {b}]" for a, b in runs(cps)], indent="    "),
        "  ] as ReadonlyArray<readonly [number, number]>,",
        "  advances: {",
    ]
    for w in WEIGHTS:
        parts.append(f"    {w}: [")
        parts.append(wrap(adv[w]))
        parts.append("    ],")
    parts += ["  } as Readonly<Record<720 | 380, readonly number[]>>,", "};", ""]
    return "\n".join(parts)


if __name__ == "__main__":
    text = build()
    if "--stdout" in sys.argv[1:]:
        sys.stdout.write(text)
    else:
        with open(OUT, "w") as f:
            f.write(text)
        print(f"wrote {os.path.relpath(OUT)}")