import logging
import shutil
import subprocess
import sys
import zipfile
from io import BytesIO
from pathlib import Path
from urllib import request


amalgamation_url = 'https://sqlite.org/2023/sqlite-amalgamation-3410000.zip'

# Extension-functions
# ===================
# It breaks amalgamation if appended as other extension because it redefines
# several functions, so build it separately. Note that sql.js registers these
# extension functions by calling ``registerExtensionFunctions`` itself.
contrib_functions_url = 'https://sqlite.org/contrib/download/extension-functions.c?get=25'

extension_urls = (
    # Miscellaneous extensions
    # ========================
    ('https://sqlite.org/src/raw/8d79354f?at=series.c', 'sqlite3_series_init'),
    ('https://sqlite.org/src/raw/dbfd8543?at=closure.c', 'sqlite3_closure_init'),
    ('https://sqlite.org/src/raw/5bb2264c?at=uuid.c', 'sqlite3_uuid_init'),
    ('https://sqlite.org/src/raw/5853b0e5?at=regexp.c', 'sqlite3_regexp_init'),
    ('https://sqlite.org/src/raw/b9086e22?at=percentile.c', 'sqlite3_percentile_init'),
    ('https://sqlite.org/src/raw/09f967dc?at=decimal.c', 'sqlite3_decimal_init'),
    # Third-party extension
    # =====================
    ('https://github.com/jakethaw/pivot_vtab/raw/9323ef93/pivot_vtab.c', 'sqlite3_pivotvtab_init'),
    ('https://github.com/nalgeon/sqlean/raw/95e8d21a/src/pearson.c', 'sqlite3_pearson_init'),
)

sqljs_url = 'https://github.com/sql-js/sql.js/archive/refs/tags/v1.7.0.zip'


def _generate_extra_init_c_function(init_function_names):
    auto_ext_calls = '\n'.join([
        'nErr += sqlite3_auto_extension((void*){});'.format(init_fn)
        for init_fn in init_function_names
    ])
    return '''
        int extra_init(const char* dummy)
        {
            int nErr = 0;
            %s
            return nErr ? SQLITE_ERROR : SQLITE_OK;
        }
    ''' % auto_ext_calls


def _get_amalgamation(tgt: Path):
    logging.info('Downloading and extracting SQLite amalgamation %s', amalgamation_url)
    archive = zipfile.ZipFile(BytesIO(request.urlopen(amalgamation_url).read()))
    archive_root_dir = zipfile.Path(archive, archive.namelist()[0])
    for zpath in archive_root_dir.iterdir():
        with zpath.open() as fr, (tgt / zpath.name).open('wb') as fw:
            shutil.copyfileobj(fr, fw)


def _get_contrib_functions(tgt: Path):
    request.urlretrieve(contrib_functions_url, tgt / 'extension-functions.c')


def _get_extensions(tgt: Path):
    init_functions = []
    sqlite3_c = tgt / 'sqlite3.c'
    with sqlite3_c.open('ab') as f:
        for url, init_fn in extension_urls:
            logging.info('Downloading and appending to amalgamation %s', url)
            with request.urlopen(url) as resp:
                shutil.copyfileobj(resp, f)
            init_functions.append(init_fn)

        logging.info('Appending SQLITE_EXTRA_INIT to amalgamation')
        f.write(_generate_extra_init_c_function(init_functions).encode())


def _get_sqljs(tgt: Path):
    logging.info('Downloading and extracting sql.js %s', sqljs_url)
    archive = zipfile.ZipFile(BytesIO(request.urlopen(sqljs_url).read()))
    archive_root_dir = zipfile.Path(archive, archive.namelist()[0])
    (tgt / 'sqljs').mkdir()
    for zpath in (archive_root_dir / 'src').iterdir():
        with zpath.open() as fr, (tgt / 'sqljs' / zpath.name).open('wb') as fw:
            shutil.copyfileobj(fr, fw)


def configure(tgt: Path):
    _get_amalgamation(tgt)
    _get_contrib_functions(tgt)
    _get_extensions(tgt)
    _get_sqljs(tgt)

    subprocess.check_call(['emcc', '--version'])


if __name__ == '__main__':
    if sys.version_info < (3, 8):
        print('Python 3.8 or higher is expected', file=sys.stderr)
        sys.exit(1)

    logging.basicConfig(level='INFO', format='%(asctime)s %(levelname)s %(name)s %(message)s')

    src = Path('src')
    src.mkdir()
    configure(src)