#!/usr/bin/env python3
"""
Build-time theme expander — merges layout sections from ui.toml into skin files.

Called by CMake during build. Reads source skin files + ui.toml, writes merged
output files to the build directory. Source files are never modified.

Usage:
    python3 expand_themes.py <source_themes_dir> <output_themes_dir>

For each .toml file in source_themes_dir (except ui.toml), the script:
  1. Copies the skin file contents (theme/palette/backdrop/effects)
  2. Appends all layout sections from ui.toml (fonts, tabs, components, etc.)
  3. Writes the merged result to output_themes_dir/<filename>

ui.toml itself is copied unchanged.
"""

import re
import sys
import os

# Sections to SKIP when extracting from ui.toml (theme-specific, already in skins)
SKIP_SECTIONS = {"theme", "theme.palette", "backdrop", "effects"}


def extract_layout_sections(ui_toml_path):
    """Extract non-theme sections from ui.toml as a string."""
    sections = []
    current_section = None
    current_lines = []
    section_re = re.compile(r'^\[{1,2}([^\]]+)\]{1,2}\s*$')

    with open(ui_toml_path, 'r') as f:
        for line in f:
            m = section_re.match(line.strip())
            if m:
                if current_section is not None or current_lines:
                    sections.append((current_section, current_lines))
                current_section = m.group(1).strip()
                current_lines = [line]
            else:
                current_lines.append(line)
    if current_section is not None or current_lines:
        sections.append((current_section, current_lines))

    layout_parts = []
    for section_name, lines in sections:
        if section_name is None:
            # Preamble: only include top-level key=value lines
            kv_lines = [l for l in lines
                        if l.strip() and not l.strip().startswith('#') and '=' in l]
            if kv_lines:
                layout_parts.append(''.join(kv_lines))
            continue
        if section_name in SKIP_SECTIONS:
            continue
        layout_parts.append(''.join(lines))

    return '\n'.join(layout_parts)


def main():
    if len(sys.argv) != 3:
        print(f"Usage: {sys.argv[0]} <source_themes_dir> <output_themes_dir>")
        sys.exit(1)

    src_dir = sys.argv[1]
    out_dir = sys.argv[2]
    ui_toml = os.path.join(src_dir, "ui.toml")

    if not os.path.exists(ui_toml):
        print(f"ERROR: ui.toml not found at {ui_toml}")
        sys.exit(1)

    os.makedirs(out_dir, exist_ok=True)

    layout_content = extract_layout_sections(ui_toml)

    separator = (
        "\n# ===========================================================================\n"
        "# Layout & Component Properties\n"
        "# All values below can be customized per-theme. Edit and save to see\n"
        "# changes reflected in the app in real time via hot-reload.\n"
        "# ===========================================================================\n\n"
    )

    for fname in sorted(os.listdir(src_dir)):
        if not fname.endswith('.toml'):
            continue
        src_path = os.path.join(src_dir, fname)
        dst_path = os.path.join(out_dir, fname)

        if fname == "ui.toml":
            # Copy ui.toml unchanged
            with open(src_path, 'r') as f:
                content = f.read()
            with open(dst_path, 'w') as f:
                f.write(content)
            print(f"  COPY {fname}")
            continue

        # Skin file — append layout sections
        with open(src_path, 'r') as f:
            skin = f.read()
        if not skin.endswith('\n'):
            skin += '\n'

        merged = skin + separator + layout_content
        if not merged.endswith('\n'):
            merged += '\n'

        with open(dst_path, 'w') as f:
            f.write(merged)
        lines = merged.count('\n')
        print(f"  MERGE {fname} → {lines} lines")

    print("Done.")


if __name__ == "__main__":
    main()