import atexit
import code
import os
import readline
import shlex

from commands import registered_cmds
import example_cmd

DEFAULT_HISTORY_FILE = "~/.psh_history"


def parse_cmd(potential_cmd):
    """Evaluates a potential command. If it exists in the list of
    registered commands, we return a string that would call the
    constructor for that command. If it does not exist, we wrap the
    name of the command with the RawCommand class.

    :return: A string that when evaluated by Python's `eval` feature
        would build an object of the correct type
    """
    args = potential_cmd.strip().split(' ')
    cmd_name = args[0]
    if args:
        args = args[1:]
    if cmd_name not in registered_cmds:
        return "RawCommand({})".format(shlex.split(potential_cmd))
    else:
        return "{0}({1})".format(cmd_name,str(args))


def parse_cmds(raw_input_line):
    """Parses command objects out of a single | separated string"""
    potential_cmds = raw_input_line.split('|')
    cmds = [parse_cmd(cmd) for cmd in potential_cmds]
    return cmds


class HistoryConsole(code.InteractiveConsole):
    """Stolen from https://docs.python.org/2/library/readline.html

    Modified for the purposes of this project to handle special
    bash-like parsing"""

    def __init__(self, locals=None, filename="<console>",
                 histfile=os.path.expanduser(DEFAULT_HISTORY_FILE)):
        code.InteractiveConsole.__init__(self, locals, filename)
        self.init_history(histfile)

    def init_history(self, histfile):
        readline.parse_and_bind("tab: complete")
        if hasattr(readline, "read_history_file"):
            try:
                readline.read_history_file(histfile)
            except IOError:
                pass
            atexit.register(self.save_history, histfile)

    def raw_input(self, prompt=""):
        """Gets a single line of input for the REPL, and returns some valid
        Python for the rest of the REPL to evaluate. It's the "R" in REPL.
        If the line begins with ">", we just strip it and evaluate as valid
        Python."""
        raw_input_line = input(prompt)
        if raw_input_line[0] == '>':
            return raw_input_line[1:]
        else:
            cmds = parse_cmds(raw_input_line)
            cmds.append("Printer()")
            mangled_input = cmds[0]
            for cmd in cmds[1:]:
                mangled_input += ".chain(" + cmd + ")"
            mangled_input += ".call()"
            print("[DEBUG]: evaluating Python: ", mangled_input)
            return mangled_input


    def save_history(self, histfile):
        readline.write_history_file(histfile)