#!/usr/bin/env python3
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"""Generate a clang header map (.hmap) for a list of include directories.

This script builds a JSON manifest and passes it off to LLVM's hmaptool.

On basename collisions the first directory listed wins, matching -I search order.
"""

import argparse
import json
import os
import subprocess
import sys

HEADER_EXTENSIONS = ('.h', '.hh', '.hpp', '.hxx', '.inc', '.def')
HMAPTOOL = os.path.join(os.path.dirname(os.path.abspath(__file__)), 'hmaptool')


def collect_mappings(directories, framework=None):
    mappings = {}
    lowercase_owners = {}
    # When --framework NAME is set, also scan a `<dir>/<NAME>/` subdirectory if
    # present. This catches the framework-staging convention where headers live
    # at `<some-include-root>/<Framework>/<Header>.h` (e.g. cmake's
    # `WebCore.framework/PrivateHeaders/WebCore/StyleTextEdge.h` symlink tree).
    # Scanning these *first* makes the curated framework-staged path win over
    # raw source-tree dirs on basename collisions.
    scan_order = []
    if framework:
        for d in directories:
            d_abs = os.path.abspath(d)
            if framework not in d_abs.split(os.sep):
                continue
            sub = os.path.join(d_abs, framework)
            if os.path.isdir(sub):
                scan_order.append(sub)
    scan_order.extend(directories)

    for directory in scan_order:
        directory = os.path.abspath(directory)
        if not os.path.isdir(directory):
            continue
        for entry in sorted(os.scandir(directory), key=lambda e: e.name):
            if not entry.name.endswith(HEADER_EXTENSIONS):
                continue
            if entry.name in mappings or not entry.is_file():
                continue
            key = entry.name.lower()
            owner = lowercase_owners.get(key)
            if owner and owner != entry.name:
                sys.stderr.write(
                    'generate-header-map: warning: case-insensitive collision between {!r} and {!r}; '
                    'clang header maps are case-insensitive, so one will shadow the other\n'.format(
                        mappings[owner], entry.path))
            lowercase_owners.setdefault(key, entry.name)
            mappings[entry.name] = entry.path
            if framework:
                # Also emit a framework-style key so `<Framework/Header.h>`
                # resolves to the source/derived path even when the header is
                # not staged into the framework's PrivateHeaders/. This matches
                # Xcode's hmap (HEADERMAP_INCLUDES_FRAMEWORK_ENTRIES_FOR_TARGET_BEING_BUILT=YES).
                mappings[f'{framework}/{entry.name}'] = entry.path
    return mappings


def main():
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument('-o', '--output', required=True, help='output .hmap path')
    parser.add_argument('--dirs-file', required=True,
                        help='file containing one include directory per line')
    parser.add_argument('--framework',
                        help='if set, also emit FRAMEWORK/Header.h entries so '
                             '<FRAMEWORK/Header.h> resolves to the source/derived path '
                             'without requiring a physical PrivateHeaders/ copy')
    args = parser.parse_args()

    with open(args.dirs_file) as f:
        directories = [line.strip() for line in f if line.strip()]

    manifest = args.output + '.json'
    with open(manifest, 'w') as f:
        json.dump({'mappings': collect_mappings(directories, args.framework)}, f, indent=2, sort_keys=True)

    return subprocess.call([sys.executable, HMAPTOOL, 'write', manifest, args.output])


if __name__ == '__main__':
    sys.exit(main())