#!/usr/bin/env python3

import json

class Metafile():
    """Representation of a metafile (default name META), containing (as its
    name implies) metadata."""


    def __init__(self, json_path=None, name=None):

        self.name = name

        # json_path  given => we load it ; otherwise fill with default
        if json_path is not None:
            self.load_json(json_path) # raise FileNotFoundError
        else:
            self.load_default()

    def load_default(self):
        self.json_path = None
        self.depends   = {}
        self.files     = {}
        # (Note that name is already written in __init__)

    def load_json(self, json_path):
        self.json_path = json_path

        tmp = json.load( open(self.json_path) ) # Can raise a FileNotFoundError

        try:
            self.name    = tmp["name"]
            self.depends = tmp["depends"]
            self.files   = tmp["files"]
        except KeyError:
            raise MalformedMetafileError("Missing attribute (name, depends or files)")
    
    def save(self):
        if self.json_path is None:
            raise NoPathDefinedError("json_path is not defined")

        json.dump( { "name": self.name, "depends": self.depends, "files": self.files }, open(self.json_path, 'w') )


    def get_files_dst2src(self):
        dstdic = {}

        try:
            for (fname, finfo) in self.files.items():
                dstdic[ finfo["dest"] ] = fname
        except KeyError:
            raise MalformedMetafileError("Missing 'dest' attribute in files infos")

        return dstdic
    
    def add_file(self, name, dest):
        self.files[name] = { "dest": dest }

    def del_file(self, name):
        del self.files[name]



# Exceptions
########################################
class MalformedMetafileError(Exception):
    """A custom exception to alert that the metafile is malformed"""

    def __init__(self, message):
        Exception.__init__(self, message)
        

class NoPathDefinedError(Exception):
    """A custom exception to alert that the json_path properties of the
    Metafile is not defined, therefore we cannot write the data."""

    def __init__(self, message):
        Exception.__init__(self, message)