"""

Part of the bsie module.
A copy of the license is provided with the project.
Author: Matthias Baumgartner, 2022
"""
# standard imports
import logging
import typing

# bsie imports
from bsie.extractor import ExtractorBuilder
from bsie.reader import ReaderBuilder
from bsie.utils import bsfs, errors

# inner-module imports
from . import pipeline

# exports
__all__: typing.Sequence[str] = (
    'PipelineBuilder',
    )


## code ##

logger = logging.getLogger(__name__)

class PipelineBuilder():
    """Build `bsie.tools.pipeline.Pipeline` instances."""

    # Prefix to be used in the Pipeline.
    prefix: bsfs.Namespace

    # builder for Readers.
    rbuild: ReaderBuilder

    # builder for Extractors.
    ebuild: ExtractorBuilder

    def __init__(
            self,
            prefix: bsfs.Namespace,
            reader_builder: ReaderBuilder,
            extractor_builder: ExtractorBuilder,
            ):
        self.prefix = prefix
        self.rbuild = reader_builder
        self.ebuild = extractor_builder

    def build(self) -> pipeline.Pipeline:
        """Return a Pipeline instance."""
        ext2rdr = {}

        for eidx in self.ebuild:
            # build extractor
            try:
                ext = self.ebuild.build(eidx)

            except errors.LoaderError as err: # failed to load extractor; skip
                logger.error('failed to load extractor: %s', err)
                continue

            except errors.BuilderError as err: # failed to build instance; skip
                logger.error(str(err))
                continue

            try:
                # get reader required by extractor
                if ext.CONTENT_READER is not None:
                    rdr = self.rbuild.build(ext.CONTENT_READER)
                else:
                    rdr = None
                # store extractor
                ext2rdr[ext] = rdr

            except errors.LoaderError as err: # failed to load reader
                logger.error('failed to load reader: %s', err)

            except errors.BuilderError as err: # failed to build reader
                logger.error(str(err))

        return pipeline.Pipeline(self.prefix, ext2rdr)

## EOF ##