# Source code for joy.utils.pretty_print

    # -*- coding: utf-8 -*-
    #
    #    Copyright © 2016 Simon Forman
    #
    #    This file is part of Thun.
    #
    #    Thun is free software: you can redistribute it and/or modify
    #    it under the terms of the GNU General Public License as published by
    #    the Free Software Foundation, either version 3 of the License, or
    #    (at your option) any later version.
    #
    #    Thun is distributed in the hope that it will be useful,
    #    but WITHOUT ANY WARRANTY; without even the implied warranty of
    #    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    #    GNU General Public License for more details.
    #
    #    You should have received a copy of the GNU General Public License
    #    along with Thun.  If not see <http://www.gnu.org/licenses/>.
    #
    '''
    Pretty printing support, e.g.::

        Joy? [23 18 * 99 +] trace
               • 23 18 mul 99 add
            23 • 18 mul 99 add
         23 18 • mul 99 add
           414 • 99 add
        414 99 • add
           513 •

        513 <-top

        joy?

    On each line the stack is printed with the top to the left, then a
    bullet symbol, •, to represent the current locus of processing, then
    the pending expression to the right.
    '''
    # (Kinda clunky and hacky.  This should be swapped out in favor of much
    # smarter stuff.)
    from traceback import print_exc
    from .stack import expression_to_string, stack_to_string
    from ..joy import joy
    from ..library import FunctionWrapper

    @FunctionWrapper
    def trace(stack, expression, dictionary):
        '''Evaluate a Joy expression on a stack and print a trace.

        This function is just like the `i` combinator but it also prints a
        trace of the evaluation

        :param stack stack: The stack.
        :param stack expression: The expression to evaluate.
        :param dict dictionary: A ``dict`` mapping names to Joy functions.
        :rtype: (stack, (), dictionary)

        '''
        tp = TracePrinter()
        quote, stack = stack
        try:
            s, _, d = joy(stack, quote, dictionary, tp.viewer)
        except:
            tp.print_()
            print('-' * 73)
            raise
        else:
            tp.print_()
        return s, expression, d

    class TracePrinter(object):
        '''
        This is what does the formatting.  You instantiate it and pass the ``viewer()``
        method to the :py:func:`joy.joy.joy` function, then print it to see the
        trace.
        '''

        def __init__(self):
            self.history = []

        def viewer(self, stack, expression):
            '''
            Record the current stack and expression in the TracePrinter's history.
            Pass this method as the ``viewer`` argument to the :py:func:`joy.joy.joy` function.

            :param stack quote: A stack.
            :param stack expression: A stack.
            '''
            self.history.append((stack, expression))

        def __str__(self):
            return '\n'.join(self.go())

        def go(self):
            '''
            Return a list of strings, one for each entry in the history, prefixed
            with enough spaces to align all the interpreter dots.

            This method is called internally by the ``__str__()`` method.

            :rtype: list(str)
            '''
            max_stack_length = 0
            lines = []
            for stack, expression in self.history:
                stack = stack_to_string(stack)
                expression = expression_to_string(expression)
                n = len(stack)
                if n > max_stack_length:
                    max_stack_length = n
                lines.append((n, '%s • %s' % (stack, expression)))
            for i in range(len(lines)):  # Prefix spaces to line up '•'s.
                length, line = lines[i]
                lines[i] =  (' ' * (max_stack_length - length) + line)
            return lines

        def print_(self):
            try:
                print(self)
            except:
                print_exc()
                print('Exception while printing viewer.')