#!/usr/bin/python
#
# Urwid advanced example column calculator application
#    Copyright (C) 2004-2009  Ian Ward
#
#    This library is free software; you can redistribute it and/or
#    modify it under the terms of the GNU Lesser General Public
#    License as published by the Free Software Foundation; either
#    version 2.1 of the License, or (at your option) any later version.
#
#    This library 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
#    Lesser General Public License for more details.
#
#    You should have received a copy of the GNU Lesser General Public
#    License along with this library; if not, write to the Free Software
#    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
#
# Urwid web site: http://excess.org/urwid/

"""
Urwid advanced example column calculator application

Features:
- multiple separate list boxes within columns
- custom edit widget for editing calculator cells
- custom parent widget for links to other columns
- custom list walker to show and hide cell results as required
- custom wrap and align modes for editing right-1 aligned numbers
- outputs commands that may be used to recreate expression on exit
"""

import urwid
import urwid.raw_display
import urwid.web_display

# use appropriate Screen class
if urwid.web_display.is_web_request():
    Screen = urwid.web_display.Screen
else:
    Screen = urwid.raw_display.Screen


def div_or_none(a,b):
    """Divide a by b.  Return result or None on divide by zero."""
    if b == 0:
        return None
    return a/b

# operators supported and the functions used to calculate a result
OPERATORS = {
    '+': (lambda a, b: a+b),
    '-': (lambda a, b: a-b),
    '*': (lambda a, b: a*b),
    '/': div_or_none,
    }

# the uppercase versions of keys used to switch columns
COLUMN_KEYS = list( "?ABCDEF" )

# these lists are used to determine when to display errors
EDIT_KEYS = OPERATORS.keys() + COLUMN_KEYS + ['backspace','delete']
MOVEMENT_KEYS = ['up','down','left','right','page up','page down']

# Event text
E_no_such_column = "Column %s does not exist."
E_no_more_columns = "Maxumum number of columns reached."
E_new_col_cell_not_empty = "Column must be started from an empty cell."
E_invalid_key = "Invalid key '%s'."
E_no_parent_column = "There is no parent column to return to."
E_cant_combine = "Cannot combine cells with sub-expressions."
E_invalid_in_parent_cell = "Cannot enter numbers into parent cell."
E_invalid_in_help_col = [
    "Help Column is in focus.  Press ",
    ('key',COLUMN_KEYS[1]),"-",('key',COLUMN_KEYS[-1]),
    " to select another column."]

# Shared layout object
CALC_LAYOUT = None


class CalcEvent(Exception):
    """Events triggered by user input."""

    attr = 'event'

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

    def widget(self):
        """Return a widget containing event information"""
        text = urwid.Text( self.message, 'center' )
        return urwid.AttrWrap( text, self.attr )

class ColumnDeleteEvent(CalcEvent):
    """Sent when user wants to delete a column"""

    attr = 'confirm'

    def __init__(self, letter, from_parent=0):
        self.message = ["Press ", ('key',"BACKSPACE"),
            " again to confirm column removal."]
        self.letter = letter

class UpdateParentEvent(Exception):
    """Sent when parent columns may need to be updated."""
    pass


class Cell:
    def __init__(self, op ):
        self.op = op
        self.is_top = op is None
        self.child = None
        self.setup_edit()
        self.result = urwid.Text("", layout=CALC_LAYOUT)

    def show_result(self, next_cell):
        """Return whether this widget should display its result.

        next_cell -- the cell following self or None"""

        if self.is_top:
            return False
        if next_cell is None:
            return True
        if self.op == "+" and next_cell.op == "+":
            return False
        return True


    def setup_edit(self):
        """Create the standard edit widget for this cell."""

        self.edit = urwid.IntEdit()
        if not self.is_top:
            self.edit.set_caption( self.op + " " )
        self.edit.set_layout( None, None, CALC_LAYOUT )

    def get_value(self):
        """Return the numeric value of the cell."""

        if self.child is not None:
            return self.child.get_result()
        else:
            return long("0"+self.edit.edit_text)

    def get_result(self):
        """Return the numeric result of this cell's operation."""

        if self.is_top:
            return self.get_value()
        if self.result.text == "":
            return None
        return long(self.result.text)

    def set_result(self, result):
        """Set the numeric result for this cell."""

        if result == None:
            self.result.set_text("")
        else:
            self.result.set_text( "%d" %result )

    def become_parent(self, column, letter):
        """Change the edit widget to a parent cell widget."""

        self.child = column
        self.edit = ParentEdit( self.op, letter )

    def remove_child(self):
        """Change the edit widget back to a standard edit widget."""

        self.child = None
        self.setup_edit()

    def is_empty( self ):
        """Return True if the cell is "empty"."""

        return self.child is None and self.edit.edit_text == ""


class ParentEdit(urwid.Edit):
    """Edit widget modified to link to a child column"""

    def __init__(self, op, letter):
        """Use the operator and letter of the child column as caption

        op -- operator or None
        letter -- letter of child column
        remove_fn -- function to call when user wants to remove child
                     function takes no parameters
        """

        urwid.Edit.__init__(self, layout=CALC_LAYOUT)
        self.op = op
        self.set_letter( letter )

    def set_letter(self, letter):
        """Set the letter of the child column for display."""

        self.letter = letter
        caption = "("+letter+")"
        if self.op is not None:
            caption = self.op+" "+caption
        self.set_caption(caption)

    def keypress(self, size, key):
        """Disable usual editing, allow only removing of child"""

        if key == "backspace":
            raise ColumnDeleteEvent(self.letter, from_parent=True)
        elif key in list("0123456789"):
            raise CalcEvent, E_invalid_in_parent_cell
        else:
            return key


class CellWalker(urwid.ListWalker):
    def __init__(self, content):
        self.content = urwid.MonitoredList(content)
        self.content.modified = self._modified
        self.focus = (0,0)
        # everyone can share the same divider widget
        self.div = urwid.Divider("-")

    def get_cell(self, i):
        if i < 0 or i >= len(self.content):
            return None
        else:
            return self.content[i]

    def _get_at_pos(self, pos):
        i, sub = pos
        assert sub in (0,1,2)
        if i < 0 or i >= len(self.content):
            return None, None
        if sub == 0:
            edit = self.content[i].edit
            return urwid.AttrWrap(edit, 'edit', 'editfocus'), pos
        elif sub == 1:
            return self.div, pos
        else:
            return self.content[i].result, pos

    def get_focus(self):
        return self._get_at_pos(self.focus)

    def set_focus(self, focus):
        self.focus = focus

    def get_next(self, start_from):
        i, sub = start_from
        assert sub in (0,1,2)
        if sub == 0:
            show_result = self.content[i].show_result(
                self.get_cell(i+1))
            if show_result:
                return self._get_at_pos( (i, 1) )
            else:
                return self._get_at_pos( (i+1, 0) )
        elif sub == 1:
            return self._get_at_pos( (i, 2) )
        else:
            return self._get_at_pos( (i+1, 0) )

    def get_prev(self, start_from):
        i, sub = start_from
        assert sub in (0,1,2)
        if sub == 0:
            if i == 0: return None, None
            show_result = self.content[i-1].show_result(
                self.content[i])
            if show_result:
                return self._get_at_pos( (i-1, 2) )
            else:
                return self._get_at_pos( (i-1, 0) )
        elif sub == 1:
            return self._get_at_pos( (i, 0) )
        else:
            return self._get_at_pos( (i, 1) )


class CellColumn( urwid.WidgetWrap ):
    def __init__(self, letter):
        self.walker = CellWalker([Cell(None)])
        self.content = self.walker.content
        self.listbox = urwid.ListBox( self.walker )
        self.set_letter( letter )
        urwid.WidgetWrap.__init__(self, self.frame)

    def set_letter(self, letter):
        """Set the column header with letter."""

        self.letter = letter
        header = urwid.AttrWrap(
            urwid.Text( ["Column ",('key',letter)],
            layout = CALC_LAYOUT), 'colhead' )
        self.frame = urwid.Frame( self.listbox, header )

    def keypress(self, size, key):
        key = self.frame.keypress( size, key)
        if key is None:
            changed = self.update_results()
            if changed:
                raise UpdateParentEvent()
            return

        f, (i, sub) = self.walker.get_focus()
        if sub != 0:
            # f is not an edit widget
            return key
        if key in OPERATORS:
            # move trailing text to new cell below
            edit = self.walker.get_cell(i).edit
            cursor_pos = edit.edit_pos
            tail = edit.edit_text[cursor_pos:]
            edit.set_edit_text( edit.edit_text[:cursor_pos] )

            new_cell = Cell( key )
            new_cell.edit.set_edit_text( tail )
            self.content[i+1:i+1] = [new_cell]

            changed = self.update_results()
            self.move_focus_next( size )
            self.content[i+1].edit.set_edit_pos(0)
            if changed:
                raise UpdateParentEvent()
            return

        elif key == 'backspace':
            # unhandled backspace, we're at beginning of number
            # append current number to cell above, removing operator
            above = self.walker.get_cell(i-1)
            if above is None:
                # we're the first cell
                raise ColumnDeleteEvent( self.letter,
                    from_parent=False )

            edit = self.walker.get_cell(i).edit
            # check that we can combine
            if above.child is not None:
                # cell above is parent
                if edit.edit_text:
                    # ..and current not empty, no good
                    raise CalcEvent, E_cant_combine
                above_pos = 0
            else:
                # above is normal number cell
                above_pos = len(above.edit.edit_text)
                above.edit.set_edit_text( above.edit.edit_text +
                    edit.edit_text )

            self.move_focus_prev( size )
            self.content[i-1].edit.set_edit_pos(above_pos)
            del self.content[i]
            changed = self.update_results()
            if changed:
                raise UpdateParentEvent()
            return

        elif key == 'delete':
            # pull text from next cell into current
            cell = self.walker.get_cell(i)
            below = self.walker.get_cell(i+1)
            if cell.child is not None:
                # this cell is a parent
                raise CalcEvent, E_cant_combine
            if below is None:
                # nothing below
                return key
            if below.child is not None:
                # cell below is a parent
                raise CalcEvent, E_cant_combine

            edit = self.walker.get_cell(i).edit
            edit.set_edit_text( edit.edit_text +
                below.edit.edit_text )

            del self.content[i+1]
            changed = self.update_results()
            if changed:
                raise UpdateParentEvent()
            return
        return key


    def move_focus_next(self, size):
        f, (i, sub) = self.walker.get_focus()
        assert i<len(self.content)-1

        ni = i
        while ni == i:
            self.frame.keypress(size, 'down')
            nf, (ni, nsub) = self.walker.get_focus()

    def move_focus_prev(self, size):
        f, (i, sub) = self.walker.get_focus()
        assert i>0

        ni = i
        while ni == i:
            self.frame.keypress(size, 'up')
            nf, (ni, nsub) = self.walker.get_focus()


    def update_results( self, start_from=None ):
        """Update column.  Return True if final result changed.

        start_from -- Cell to start updating from or None to start from
                      the current focus (default None)
        """

        if start_from is None:
            f, (i, sub) = self.walker.get_focus()
        else:
            i = self.content.index(start_from)
            if i == None: return False

        focus_cell = self.walker.get_cell(i)

        if focus_cell.is_top:
            x = focus_cell.get_value()
            last_op = None
        else:
            last_cell = self.walker.get_cell(i-1)
            x = last_cell.get_result()

            if x is not None and focus_cell.op is not None:
                x = OPERATORS[focus_cell.op]( x,
                    focus_cell.get_value() )
            focus_cell.set_result(x)

        for cell in self.content[i+1:]:
            if cell.op is None:
                x = None
            if x is not None:
                x = OPERATORS[cell.op]( x, cell.get_value() )
            if cell.get_result() == x:
                return False
            cell.set_result(x)

        return True


    def create_child( self, letter ):
        """Return (parent cell,child column) or None,None on failure."""
        f, (i, sub) = self.walker.get_focus()
        if sub != 0:
            # f is not an edit widget
            return None, None

        cell = self.walker.get_cell(i)
        if cell.child is not None:
            raise CalcEvent, E_new_col_cell_not_empty
        if cell.edit.edit_text:
            raise CalcEvent, E_new_col_cell_not_empty

        child = CellColumn( letter )
        cell.become_parent( child, letter )

        return cell, child

    def is_empty( self ):
        """Return True if this column is empty."""

        return len(self.content)==1 and self.content[0].is_empty()


    def get_expression(self):
        """Return the expression as a printable string."""

        l = []
        for c in self.content:
            if c.op is not None: # only applies to first cell
                l.append(c.op)
            if c.child is not None:
                l.append("("+c.child.get_expression()+")")
            else:
                l.append("%d"%c.get_value())

        return "".join(l)

    def get_result(self):
        """Return the result of the last cell in the column."""

        return self.content[-1].get_result()




class HelpColumn(urwid.BoxWidget):
    help_text = [
        ('title', "Column Calculator"),
        "",
        [ "Numbers: ", ('key', "0"), "-", ('key', "9") ],
        "" ,
        [ "Operators: ",('key', "+"), ", ", ('key', "-"), ", ",
            ('key', "*"), " and ", ('key', "/")],
        "",
        [ "Editing: ", ('key', "BACKSPACE"), " and ",('key', "DELETE")],
        "",
        [ "Movement: ", ('key', "UP"), ", ", ('key', "DOWN"), ", ",
            ('key', "LEFT"), ", ", ('key', "RIGHT"), ", ",
            ('key', "PAGE UP"), " and ", ('key', "PAGE DOWN") ],
        "",
        [ "Sub-expressions: ", ('key', "("), " and ", ('key', ")") ],
        "",
        [ "Columns: ", ('key', COLUMN_KEYS[0]), " and ",
            ('key',COLUMN_KEYS[1]), "-",
            ('key',COLUMN_KEYS[-1]) ],
        "",
        [ "Exit: ", ('key', "Q") ],
        "",
        "",
        ["Column Calculator does operations in the order they are ",
            "typed, not by following usual precedence rules.  ",
            "If you want to calculate ", ('key', "12 - 2 * 3"),
            " with the multiplication happening before the ",
            "subtraction you must type ",
            ('key', "12 - (2 * 3)"), " instead."],
        ]

    def __init__(self):
        self.head = urwid.AttrWrap(
            urwid.Text(["Help Column ", ('key',"?")],
                layout = CALC_LAYOUT),
            'help')
        self.foot = urwid.AttrWrap(
            urwid.Text(["[text continues.. press ",
            ('key',"?"), " then scroll]"]), 'helpnote' )
        self.items = [urwid.Text(x) for x in self.help_text]
        self.listbox = urwid.ListBox(urwid.SimpleListWalker(self.items))
        self.body = urwid.AttrWrap( self.listbox, 'help' )
        self.frame = urwid.Frame( self.body, header=self.head)

    def render(self, size, focus=False):
        maxcol, maxrow = size
        head_rows = self.head.rows((maxcol,))
        if "bottom" in self.listbox.ends_visible(
            (maxcol, maxrow-head_rows) ):
            self.frame.footer = None
        else:
            self.frame.footer = self.foot

        return self.frame.render( (maxcol, maxrow), focus)

    def keypress( self, size, key ):
        return self.frame.keypress( size, key )


class CalcDisplay:
    palette = [
        ('body','white', 'dark blue'),
        ('edit','yellow', 'dark blue'),
        ('editfocus','yellow','dark cyan', 'bold'),
        ('key','dark cyan', 'light gray', ('standout','underline')),
        ('title', 'white', 'light gray', ('bold','standout')),
        ('help', 'black', 'light gray', 'standout'),
        ('helpnote', 'dark green', 'light gray'),
        ('colhead', 'black', 'light gray', 'standout'),
        ('event', 'light red', 'black', 'standout'),
        ('confirm', 'yellow', 'black', 'bold'),
        ]

    def __init__(self):
        self.columns = urwid.Columns([HelpColumn(), CellColumn("A")], 1)
        self.col_list = self.columns.widget_list
        self.columns.set_focus_column( 1 )
        view = urwid.AttrWrap(self.columns, 'body')
        self.view = urwid.Frame(view) # for showing messages
        self.col_link = {}

    def main(self):
        self.loop = urwid.MainLoop(self.view, self.palette, screen=Screen(),
            input_filter=self.input_filter)
        self.loop.run()

        # on exit write the formula and the result to the console
        expression, result = self.get_expression_result()
        print "Paste this expression into a new Column Calculator session to continue editing:"
        print expression
        print "Result:", result

    def input_filter(self, input, raw_input):
        if 'q' in input or 'Q' in input:
            raise urwid.ExitMainLoop()

        # handle other keystrokes
        for k in input:
            try:
                self.wrap_keypress(k)
                self.event = None
                self.view.footer = None
            except CalcEvent, e:
                # display any message
                self.event = e
                self.view.footer = e.widget()

        # remove all input from further processing by MainLoop
        return []

    def wrap_keypress(self, key):
        """Handle confirmation and throw event on bad input."""

        try:
            key = self.keypress(key)

        except ColumnDeleteEvent, e:
            if e.letter == COLUMN_KEYS[1]:
                # cannot delete the first column, ignore key
                return

            if not self.column_empty( e.letter ):
                # need to get two in a row, so check last event
                if not isinstance(self.event,ColumnDeleteEvent):
                    # ask for confirmation
                    raise e
            self.delete_column(e.letter)

        except UpdateParentEvent, e:
            self.update_parent_columns()
            return

        if key is None:
            return

        if self.columns.get_focus_column() == 0:
            if key not in ('up','down','page up','page down'):
                raise CalcEvent, E_invalid_in_help_col

        if key not in EDIT_KEYS and key not in MOVEMENT_KEYS:
            raise CalcEvent, E_invalid_key % key.upper()

    def keypress(self, key):
        """Handle a keystroke."""

        self.loop.process_input([key])

        if key.upper() in COLUMN_KEYS:
            # column switch
            i = COLUMN_KEYS.index(key.upper())
            if i >= len( self.col_list ):
                raise CalcEvent, E_no_such_column % key.upper()
            self.columns.set_focus_column( i )
            return
        elif key == "(":
            # open a new column
            if len( self.col_list ) >= len(COLUMN_KEYS):
                raise CalcEvent, E_no_more_columns
            i = self.columns.get_focus_column()
            if i == 0:
                # makes no sense in help column
                return key
            col = self.col_list[i]
            new_letter = COLUMN_KEYS[len(self.col_list)]
            parent, child = col.create_child( new_letter )
            if child is None:
                # something invalid in focus
                return key
            self.col_list.append(child)
            self.set_link( parent, col, child )
            self.columns.set_focus_column(len(self.col_list)-1)

        elif key == ")":
            i = self.columns.get_focus_column()
            if i == 0:
                # makes no sense in help column
                return key
            col = self.col_list[i]
            parent, pcol = self.get_parent( col )
            if parent is None:
                # column has no parent
                raise CalcEvent, E_no_parent_column

            new_i = self.col_list.index( pcol )
            self.columns.set_focus_column( new_i )
        else:
            return key

    def set_link( self, parent, pcol, child ):
        """Store the link between a parent cell and child column.

        parent -- parent Cell object
        pcol -- CellColumn where parent resides
        child -- child CellColumn object"""

        self.col_link[ child ] = parent, pcol

    def get_parent( self, child ):
        """Return the parent and parent column for a given column."""

        return self.col_link.get( child, (None,None) )

    def column_empty(self, letter):
        """Return True if the column passed is empty."""

        i = COLUMN_KEYS.index(letter)
        col = self.col_list[i]
        return col.is_empty()


    def delete_column(self, letter):
        """Delete the column with the given letter."""

        i = COLUMN_KEYS.index(letter)
        col = self.col_list[i]

        parent, pcol = self.get_parent( col )

        f = self.columns.get_focus_column()
        if f == i:
            # move focus to the parent column
            f = self.col_list.index(pcol)
            self.columns.set_focus_column(f)

        parent.remove_child()
        pcol.update_results(parent)
        del self.col_list[i]

        # delete children of this column
        keep_right_cols = []
        remove_cols = [col]
        for rcol in self.col_list[i:]:
            parent, pcol = self.get_parent( rcol )
            if pcol in remove_cols:
                remove_cols.append( rcol )
            else:
                keep_right_cols.append( rcol )
        for rc in remove_cols:
            # remove the links
            del self.col_link[rc]
        # keep only the non-children
        self.col_list[i:] = keep_right_cols

        # fix the letter assignments
        for j in range(i, len(self.col_list)):
            col = self.col_list[j]
            # fix the column heading
            col.set_letter( COLUMN_KEYS[j] )
            parent, pcol = self.get_parent( col )
            # fix the parent cell
            parent.edit.set_letter( COLUMN_KEYS[j] )

    def update_parent_columns(self):
        "Update the parent columns of the current focus column."

        f = self.columns.get_focus_column()
        col = self.col_list[f]
        while 1:
            parent, pcol = self.get_parent(col)
            if pcol is None:
                return

            changed = pcol.update_results( start_from = parent )
            if not changed:
                return
            col = pcol


    def get_expression_result(self):
        """Return (expression, result) as strings."""

        col = self.col_list[1]
        return col.get_expression(), "%d"%col.get_result()



class CalcNumLayout(urwid.TextLayout):
    """
    TextLayout class for bottom-right aligned numbers with a space on
    the last line for the cursor.
    """
    def layout( self, text, width, align, wrap ):
        """
        Return layout structure for calculator number display.
        """
        lt = len(text) + 1 # extra space for cursor
        r = (lt) % width # remaining segment not full width wide
        linestarts = range( r, lt, width )
        l = []
        if linestarts:
            if r:
                # right-align the remaining segment on 1st line
                l.append( [(width-r,None),(r, 0, r)] )
            # fill all but the last line
            for x in linestarts[:-1]:
                l.append( [(width, x, x+width)] )
            s = linestarts[-1]
            # add the last line with a cursor hint
            l.append( [(width-1, s, lt-1), (0, lt-1)] )
        elif lt-1:
            # all fits on one line, so right align the text
            # with a cursor hint at the end
            l.append( [(width-lt,None),(lt-1,0,lt-1), (0,lt-1)] )
        else:
            # nothing on the line, right align a cursor hint
            l.append( [(width-1,None),(0,0)] )

        return l




def main():
    """Launch Column Calculator."""
    global CALC_LAYOUT
    CALC_LAYOUT = CalcNumLayout()

    urwid.web_display.set_preferences("Column Calculator")
    # try to handle short web requests quickly
    if urwid.web_display.handle_short_request():
        return

    CalcDisplay().main()

if '__main__'==__name__ or urwid.web_display.is_web_request():
    main()