#!/usr/bin/env python
#
# Pre-build script: gzip webui/index.html into a PROGMEM C header so the
# webconfig portal can serve the page straight from flash with
# Content-Encoding: gzip. The generated header is .gitignored; this script
# regenerates it whenever the source page (or this script) content changes.
#
# Freshness is decided by a content hash of the build inputs (not timestamps):
# a generated header written with a skewed/future mtime would otherwise mask a
# later source edit and embed stale UI. gzip output is deterministic (mtime=0),
# so an unchanged source produces an unchanged header.
#
# The generator is idempotent and cheap: when the inputs are unchanged it only
# hashes two small files and returns, so running it from esp32_base on every
# ESP32 build is negligible even for targets that don't compile the portal.
#
# Comments and indentation are stripped before compressing (see strip_source).
# The source page is heavily commented by house style and none of it is worth
# flash, so the page ships smaller than it reads.
#
# Output: src/helpers/esp32/WebConfigHtml.h
#   WEBCONFIG_HTML_GZ[]   - gzipped page (PROGMEM)
#   WEBCONFIG_HTML_GZ_LEN - byte length
#   WEBCONFIG_HTML_ETAG   - quoted strong ETag (sha256 prefix of the gz body)
#
# Runnable outside SCons to inspect exactly what gets shipped:
#   python3 scripts/generate_webconfig_html.py --emit /tmp/shipped.html
# or served directly by the mock backend with its --minify flag.

import gzip
import hashlib
import os
import sys

try:
    Import("env")  # noqa: F821
except NameError:
    pass           # running standalone (--emit), not as a PIO extra_script

SOURCE = os.path.join("webui", "index.html")
OUTPUT = os.path.join("src", "helpers", "esp32", "WebConfigHtml.h")
# __file__ is not defined inside PIO/SCons-executed extra_scripts
SCRIPT = os.path.join("scripts", "generate_webconfig_html.py")
MINIFIER = os.path.join("scripts", "webconfig_minify.py")
HASH_MARKER = "// build-inputs-sha256: "

sys.path.insert(0, os.path.join(os.getcwd(), "scripts"))
from webconfig_minify import check_stripped, strip_source  # noqa: E402


def status(msg):
    sys.stderr.write("WebConfig HTML: %s\n" % msg)


def content_hash():
    # Hash the source page, this generator and the minifier so any change to
    # any of them forces a regenerate, independent of file timestamps.
    h = hashlib.sha256()
    with open(SOURCE, "rb") as f:
        h.update(f.read())
    for path in (SCRIPT, MINIFIER):
        if os.path.isfile(path):
            h.update(b"\0")
            with open(path, "rb") as f:
                h.update(f.read())
    return h.hexdigest()


def stored_hash():
    try:
        with open(OUTPUT, "r") as f:
            for line in f:
                if line.startswith(HASH_MARKER):
                    return line[len(HASH_MARKER):].strip()
                if line.startswith("#"):  # reached the C preprocessor lines
                    break
    except OSError:
        return None
    return None


def shipped_page():
    """The exact bytes the device serves: the source page, stripped."""
    with open(SOURCE, "r", encoding="utf-8") as f:
        raw = f.read()
    stripped = strip_source(raw)
    problem = check_stripped(raw, stripped)
    if problem:
        status("ERROR: comment stripping corrupted the page (%s)" % problem)
        sys.exit(2)
    return raw, stripped


def main():
    if not os.path.isfile(SOURCE):
        status("ERROR: %s not found" % SOURCE)
        sys.exit(2)

    if "--emit" in sys.argv:
        dest = sys.argv[sys.argv.index("--emit") + 1]
        src, stripped = shipped_page()
        with open(dest, "w", encoding="utf-8") as f:
            f.write(stripped)
        status("%s -> %s (%d -> %d bytes)" % (SOURCE, dest, len(src), len(stripped)))
        return

    src_hash = content_hash()
    if os.path.isfile(OUTPUT) and stored_hash() == src_hash:
        return

    src, stripped = shipped_page()
    raw = stripped.encode("utf-8")

    # mtime=0 keeps the gzip output (and therefore the ETag) deterministic
    gz = gzip.compress(raw, compresslevel=9, mtime=0)
    etag = hashlib.sha256(gz).hexdigest()[:16]

    lines = []
    lines.append("// Auto-generated by scripts/generate_webconfig_html.py from %s" % SOURCE.replace(os.sep, "/"))
    lines.append("// DO NOT EDIT - edit webui/index.html instead.")
    lines.append("%s%s" % (HASH_MARKER, src_hash))
    lines.append("#pragma once")
    lines.append("#include <stdint.h>")
    lines.append("#include <pgmspace.h>")
    lines.append("")
    lines.append("const uint32_t WEBCONFIG_HTML_GZ_LEN = %d;" % len(gz))
    lines.append('const char WEBCONFIG_HTML_ETAG[] = "\\"%s\\"";' % etag)
    lines.append("const uint8_t WEBCONFIG_HTML_GZ[] PROGMEM = {")
    for i in range(0, len(gz), 16):
        chunk = gz[i:i + 16]
        lines.append("  " + "".join("0x%02x," % b for b in chunk))
    lines.append("};")
    lines.append("")

    os.makedirs(os.path.dirname(OUTPUT), exist_ok=True)
    with open(OUTPUT, "w") as f:
        f.write("\n".join(lines))

    status("%s -> %s (%d bytes source, %d stripped, %d gzipped)"
           % (SOURCE, OUTPUT, len(src.encode("utf-8")), len(raw), len(gz)))


main()