import inspect
from types import GeneratorType
import xml.etree.ElementTree as ETree
from asf_search import ASF_LOGGER
from asf_search.export.export_translators import ASFSearchResults_to_properties_list


def results_to_metalink(results):
    ASF_LOGGER.info('Started translating results to metalink format')

    if inspect.isgeneratorfunction(results) or isinstance(results, GeneratorType):
        return MetalinkStreamArray(results)

    return MetalinkStreamArray([results])


class MetalinkStreamArray(list):
    def __init__(self, results):
        self.pages = results
        self.len = 1
        self.header = (
            '<?xml version="1.0"?>'
            '<metalink xmlns="http://www.metalinker.org/" version="3.0">\n'
            '<publisher><name>Alaska Satellite Facility</name><url>http://www.asf.alaska.edu/</url></publisher>\n'  # noqa F401
            '<files>'
        )

        self.footer = '\n</files>\n</metalink>'

    def get_additional_fields(self, product):
        return {}

    def __iter__(self):
        return self.streamPages()

    def __len__(self):
        return self.len

    def streamPages(self):
        yield self.header

        completed = False
        for page_idx, page in enumerate(self.pages):
            ASF_LOGGER.info(f'Streaming {len(page)} products from page {page_idx}')
            completed = page.searchComplete

            properties_list = ASFSearchResults_to_properties_list(page, self.get_additional_fields)
            yield from [self.getItem(p) for p in properties_list]

        if not completed:
            ASF_LOGGER.warn('Failed to download all results from CMR')

        yield self.footer

        ASF_LOGGER.info(f'Finished streaming {self.getOutputType()} results')

    def getOutputType(self) -> str:
        return 'metalink'

    def getItem(self, p):
        file = ETree.Element('file', attrib={'name': p['fileName']})
        resources = ETree.Element('resources')

        url = ETree.Element('url', attrib={'type': 'http'})
        url.text = p['url']
        resources.append(url)
        file.append(resources)

        if p.get('md5sum') and p.get('md5sum') != 'NA':
            verification = ETree.Element('verification')
            h = ETree.Element('hash', {'type': 'md5'})
            h.text = p['md5sum']
            verification.append(h)
            file.append(verification)

        if p['bytes'] and p['bytes'] != 'NA':
            size = ETree.Element('size')
            size.text = str(p['bytes'])
            file.append(size)

        return '\n' + (8 * ' ') + ETree.tostring(file, encoding='unicode')

    def indent(self, elem, level=0):
        # Only Python 3.9+ has a built-in indent function for element tree.
        # https://stackoverflow.com/a/33956544
        i = '\n' + level * '  '
        if len(elem):
            if not elem.text or not elem.text.strip():
                elem.text = i + '  '
            if not elem.tail or not elem.tail.strip():
                elem.tail = i
            for elem in elem:
                self.indent(elem, level + 1)
            if not elem.tail or not elem.tail.strip():
                elem.tail = i
        else:
            if level and (not elem.tail or not elem.tail.strip()):
                elem.tail = i
