import sys
import argparse
from pathlib import Path
from pydoc import pager
from ..configuration import Config
from ..glossary import Glossary


class GlossaryCmdError(Exception):
    pass


def print_paged(text: str) -> None:
    pager(text)


def get_glossary_file_path(name: str, config: Config) -> Path:
    """
    Get the complete filename for a glossary with the given path.
    """
    if not config.glossaries:
        raise GlossaryCmdError("Can't create glossary name without a glossary directory")
    return Path(config.glossaries, name).with_suffix(Glossary.file_suffix).absolute()


def list_glossaries(args: argparse.Namespace, config: Config) -> None:
    """
    List existing glossaries in the 'glossaries' directory.
    """
    if not config.glossaries:
        raise GlossaryCmdError("Glossaries directory missing in the configuration file")
    glossaries = Path(config.glossaries).glob(f'*{Glossary.file_suffix}')
    for glo in sorted(glossaries):
        print(Glossary.from_file(glo).to_str())


def print_glossary(args: argparse.Namespace, config: Config) -> None:
    """
    Print an existing glossary.
    """
    # sanity checks
    if args.name is None:
        raise GlossaryCmdError("Missing glossary name")
    if config.glossaries is None and args.file is None:
        raise GlossaryCmdError("Glossaries directory missing in the configuration file")
    # create file path or use the given one
    glo_file = Path(args.file) if args.file else get_glossary_file_path(args.name, config)
    if not glo_file.exists():
        raise GlossaryCmdError(f"Glossary '{glo_file}' does not exist")
    # read glossary
    glo = Glossary.from_file(glo_file)
    print_paged(glo.to_str(with_entries=True))


def create_glossary(args: argparse.Namespace, config: Config) -> None:
    """
    Create a new glossary and write it either to the glossaries directory
    or the given file.
    """
    # sanity checks
    if args.name is None:
        raise GlossaryCmdError("Missing glossary name")
    if args.source_lang is None:
        raise GlossaryCmdError("Missing source language")
    if args.target_lang is None:
        raise GlossaryCmdError("Missing target language")
    if config.glossaries is None and args.file is None:
        raise GlossaryCmdError("Glossaries directory missing in the configuration file")
    # create file path or use the given one
    glo_file = Path(args.file) if args.file else get_glossary_file_path(args.name, config)
    if glo_file.exists():
        raise GlossaryCmdError(f"Glossary '{glo_file}' already exists")
    glo = Glossary(name=args.name,
                   source_lang=args.source_lang,
                   target_lang=args.target_lang,
                   desc=args.description,
                   file_path=glo_file)
    glo.to_file()
    print(f"Successfully created new glossary '{glo_file}'.")


def glossary_cmd(args: argparse.Namespace, config: Config) -> None:
    """
    Handler for the 'glossary' command.
    """
    try:
        if args.create:
            create_glossary(args, config)
        elif args.list:
            list_glossaries(args, config)
    except GlossaryCmdError as err:
        print(f"Error: {err}")
        sys.exit(1)