#!/usr/bin/python
# -*- coding: utf-8 -*-
#
# Urwid utility functions
#    Copyright (C) 2004-2011  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/

from urwid import escape
from urwid.compat import bytes

import codecs

str_util = escape.str_util

# bring str_util functions into our namespace
calc_text_pos = str_util.calc_text_pos
calc_width = str_util.calc_width
is_wide_char = str_util.is_wide_char
move_next_char = str_util.move_next_char
move_prev_char = str_util.move_prev_char
within_double_byte = str_util.within_double_byte


def detect_encoding():
    # Try to determine if using a supported double-byte encoding
    import locale
    try:
        try:
            locale.setlocale(locale.LC_ALL, "")
        except locale.Error:
            pass
        return locale.getlocale()[1] or ""
    except ValueError as e:
        # with invalid LANG value python will throw ValueError
        if e.args and e.args[0].startswith("unknown locale"):
            return ""
        else:
            raise

if 'detected_encoding' not in locals():
    detected_encoding = detect_encoding()
else:
    assert 0, "It worked!"

_target_encoding = None
_use_dec_special = True


def set_encoding( encoding ):
    """
    Set the byte encoding to assume when processing strings and the
    encoding to use when converting unicode strings.
    """
    encoding = encoding.lower()

    global _target_encoding, _use_dec_special

    if encoding in ( 'utf-8', 'utf8', 'utf' ):
        str_util.set_byte_encoding("utf8")
            
        _use_dec_special = False
    elif encoding in ( 'euc-jp' # JISX 0208 only
            , 'euc-kr', 'euc-cn', 'euc-tw' # CNS 11643 plain 1 only
            , 'gb2312', 'gbk', 'big5', 'cn-gb', 'uhc'
            # these shouldn't happen, should they?
            , 'eucjp', 'euckr', 'euccn', 'euctw', 'cncb' ):
        str_util.set_byte_encoding("wide")
            
        _use_dec_special = True
    else:
        str_util.set_byte_encoding("narrow")
        _use_dec_special = True

    # if encoding is valid for conversion from unicode, remember it
    _target_encoding = 'ascii'
    try:    
        if encoding:
            "".encode(encoding)
            _target_encoding = encoding
    except LookupError: pass


def get_encoding_mode():
    """
    Get the mode Urwid is using when processing text strings.
    Returns 'narrow' for 8-bit encodings, 'wide' for CJK encodings
    or 'utf8' for UTF-8 encodings.
    """
    return str_util.get_byte_encoding()


def apply_target_encoding( s ):
    """
    Return (encoded byte string, character set rle).
    """
    if _use_dec_special and type(s) == str:
        # first convert drawing characters
        try:
            s = s.translate( escape.DEC_SPECIAL_CHARMAP )
        except NotImplementedError:
            # python < 2.4 needs to do this the hard way..
            for c, alt in zip(escape.DEC_SPECIAL_CHARS, 
                    escape.ALT_DEC_SPECIAL_CHARS):
                s = s.replace( c, escape.SO+alt+escape.SI )

    if type(s) == str:
        s = s.replace(escape.SI+escape.SO, "") # remove redundant shifts
        s = codecs.encode(s, _target_encoding, 'replace')

    assert isinstance(s, bytes)
    SO = escape.SO.encode('ascii')
    SI = escape.SI.encode('ascii')

    sis = s.split(SO)

    assert isinstance(sis[0], bytes)

    sis0 = sis[0].replace(SI, bytes())
    sout = []
    cout = []
    if sis0:
        sout.append( sis0 )
        cout.append( (None,len(sis0)) )
    
    if len(sis)==1:
        return sis0, cout
    
    for sn in sis[1:]:
        assert isinstance(sn, bytes)
        assert isinstance(SI, bytes)
        sl = sn.split(SI, 1)
        if len(sl) == 1:
            sin = sl[0]
            assert isinstance(sin, bytes)
            sout.append(sin)
            rle_append_modify(cout, (escape.DEC_TAG.encode('ascii'), len(sin)))
            continue
        sin, son = sl
        son = son.replace(SI, bytes())
        if sin:
            sout.append(sin)
            rle_append_modify(cout, (escape.DEC_TAG, len(sin)))
        if son:
            sout.append(son)
            rle_append_modify(cout, (None, len(son)))

    outstr = bytes().join(sout)
    return outstr, cout


######################################################################
# Try to set the encoding using the one detected by the locale module
set_encoding( detected_encoding )
######################################################################


def supports_unicode():
    """
    Return True if python is able to convert non-ascii unicode strings
    to the current encoding.
    """
    return _target_encoding and _target_encoding != 'ascii'





def calc_trim_text( text, start_offs, end_offs, start_col, end_col ):
    """
    Calculate the result of trimming text.
    start_offs -- offset into text to treat as screen column 0
    end_offs -- offset into text to treat as the end of the line
    start_col -- screen column to trim at the left
    end_col -- screen column to trim at the right

    Returns (start, end, pad_left, pad_right), where:
    start -- resulting start offset
    end -- resulting end offset
    pad_left -- 0 for no pad or 1 for one space to be added
    pad_right -- 0 for no pad or 1 for one space to be added
    """
    spos = start_offs
    pad_left = pad_right = 0
    if start_col > 0:
        spos, sc = calc_text_pos( text, spos, end_offs, start_col )
        if sc < start_col:
            pad_left = 1
            spos, sc = calc_text_pos( text, start_offs, 
                end_offs, start_col+1 )
    run = end_col - start_col - pad_left
    pos, sc = calc_text_pos( text, spos, end_offs, run )
    if sc < run:
        pad_right = 1
    return ( spos, pos, pad_left, pad_right )




def trim_text_attr_cs( text, attr, cs, start_col, end_col ):
    """
    Return ( trimmed text, trimmed attr, trimmed cs ).
    """
    spos, epos, pad_left, pad_right = calc_trim_text( 
        text, 0, len(text), start_col, end_col )
    attrtr = rle_subseg( attr, spos, epos )
    cstr = rle_subseg( cs, spos, epos )
    if pad_left:
        al = rle_get_at( attr, spos-1 )
        rle_append_beginning_modify( attrtr, (al, 1) )
        rle_append_beginning_modify( cstr, (None, 1) )
    if pad_right:
        al = rle_get_at( attr, epos )
        rle_append_modify( attrtr, (al, 1) )
        rle_append_modify( cstr, (None, 1) )

    return (bytes().rjust(pad_left) + text[spos:epos] +
        bytes().rjust(pad_right), attrtr, cstr)


def rle_get_at( rle, pos ):
    """
    Return the attribute at offset pos.
    """
    x = 0
    if pos < 0:
        return None
    for a, run in rle:
        if x+run > pos:
            return a
        x += run
    return None


def rle_subseg( rle, start, end ):
    """Return a sub segment of an rle list."""
    l = []
    x = 0
    for a, run in rle:
        if start:
            if start >= run:
                start -= run
                x += run
                continue
            x += start
            run -= start
            start = 0
        if x >= end:
            break
        if x+run > end:
            run = end-x
        x += run    
        l.append( (a, run) )
    return l


def rle_len( rle ):
    """
    Return the number of characters covered by a run length
    encoded attribute list.
    """
    
    run = 0
    for v in rle:
        assert type(v) == tuple, repr(rle)
        a, r = v
        run += r
    return run

def rle_append_beginning_modify( rle, xxx_todo_changeme ):
    """
    Append (a, r) to BEGINNING of rle.
    Merge with first run when possible

    MODIFIES rle parameter contents. Returns None.
    """
    (a, r) = xxx_todo_changeme
    if not rle:
        rle[:] = [(a, r)]
    else:    
        al, run = rle[0]
        if a == al:
            rle[0] = (a,run+r)
        else:
            rle[0:0] = [(al, r)]
            
            
def rle_append_modify( rle, xxx_todo_changeme1 ):
    """
    Append (a,r) to the rle list rle.
    Merge with last run when possible.
    
    MODIFIES rle parameter contents. Returns None.
    """
    (a, r) = xxx_todo_changeme1
    if not rle or rle[-1][0] != a:
        rle.append( (a,r) )
        return
    la,lr = rle[-1]
    rle[-1] = (a, lr+r)

def rle_join_modify( rle, rle2 ):
    """
    Append attribute list rle2 to rle.
    Merge last run of rle with first run of rle2 when possible.

    MODIFIES attr parameter contents. Returns None.
    """
    if not rle2:
        return
    rle_append_modify(rle, rle2[0])
    rle += rle2[1:]
        
def rle_product( rle1, rle2 ):
    """
    Merge the runs of rle1 and rle2 like this:
    eg.
    rle1 = [ ("a", 10), ("b", 5) ]
    rle2 = [ ("Q", 5), ("P", 10) ]
    rle_product: [ (("a","Q"), 5), (("a","P"), 5), (("b","P"), 5) ]

    rle1 and rle2 are assumed to cover the same total run.
    """
    i1 = i2 = 1 # rle1, rle2 indexes
    if not rle1 or not rle2: return []
    a1, r1 = rle1[0]
    a2, r2 = rle2[0]
    
    l = []
    while r1 and r2:
        r = min(r1, r2)
        rle_append_modify( l, ((a1,a2),r) )
        r1 -= r
        if r1 == 0 and i1< len(rle1):
            a1, r1 = rle1[i1]
            i1 += 1
        r2 -= r
        if r2 == 0 and i2< len(rle2):
            a2, r2 = rle2[i2]
            i2 += 1
    return l    


def rle_factor( rle ):
    """
    Inverse of rle_product.
    """
    rle1 = []
    rle2 = []
    for (a1, a2), r in rle:
        rle_append_modify( rle1, (a1, r) )
        rle_append_modify( rle2, (a2, r) )
    return rle1, rle2


class TagMarkupException(Exception): pass

def decompose_tagmarkup(tm):
    """Return (text string, attribute list) for tagmarkup passed."""

    tl, al = _tagmarkup_recurse(tm, None)
    # join as unicode or bytes based on type of first element
    text = tl[0][:0].join(tl)

    if al and al[-1][0] is None:
        del al[-1]

    return text, al

def _tagmarkup_recurse( tm, attr ):
    """Return (text list, attribute list) for tagmarkup passed.
    
    tm -- tagmarkup
    attr -- current attribute or None"""
    
    if type(tm) == list:
        # for lists recurse to process each subelement
        rtl = [] 
        ral = []
        for element in tm:
            tl, al = _tagmarkup_recurse( element, attr )
            if ral:
                # merge attributes when possible
                last_attr, last_run = ral[-1]
                top_attr, top_run = al[0]
                if last_attr == top_attr:
                    ral[-1] = (top_attr, last_run + top_run)
                    del al[-1]
            rtl += tl
            ral += al
        return rtl, ral
        
    if type(tm) == tuple:
        # tuples mark a new attribute boundary
        if len(tm) != 2: 
            raise TagMarkupException("Tuples must be in the form (attribute, tagmarkup): %r" % (tm,))

        attr, element = tm
        return _tagmarkup_recurse( element, attr )
    
    if not isinstance(tm,(str, bytes)):
        raise TagMarkupException("Invalid markup element: %r" % tm)
    
    # text
    return [tm], [(attr, len(tm))]



def is_mouse_event( ev ):
    return type(ev) == tuple and len(ev)==4 and ev[0].find("mouse")>=0

def is_mouse_press( ev ):
    return ev.find("press")>=0



class MetaSuper(type):
    """adding .__super"""
    def __init__(cls, name, bases, d):
        super(MetaSuper, cls).__init__(name, bases, d)
        if hasattr(cls, "_%s__super" % name):
            raise AttributeError("Class has same name as one of its super classes")
        setattr(cls, "_%s__super" % name, super(cls))


    
def int_scale(val, val_range, out_range):
    """
    Scale val in the range [0, val_range-1] to an integer in the range 
    [0, out_range-1].  This implementaton uses the "round-half-up" rounding 
    method.

    >>> "%x" % int_scale(0x7, 0x10, 0x10000)
    '7777'
    >>> "%x" % int_scale(0x5f, 0x100, 0x10)
    '6'
    >>> int_scale(2, 6, 101)
    40
    >>> int_scale(1, 3, 4)
    2
    """
    num = int(val * (out_range-1) * 2 + (val_range-1))
    dem = ((val_range-1) * 2)
    # if num % dem == 0 then we are exactly half-way and have rounded up.
    return num // dem

