# vim:fileencoding=utf-8
# License: GPL v3 Copyright: 2016, Kovid Goyal <kovid at kovidgoyal.net>
from __python__ import hash_literals

import traceback
from elementmaker import E
from select import word_at_point

from dom import set_css
from read_book.cfi import (
    at_current as cfi_at_current, at_point as cfi_at_point,
    scroll_to as cfi_scroll_to
)
from read_book.globals import get_boss
from read_book.settings import opts
from read_book.viewport import scroll_viewport
from utils import document_width, get_elem_data, set_elem_data, viewport_to_document


def first_child(parent):
    c = parent.firstChild
    count = 0
    while c?.nodeType is not Node.ELEMENT_NODE and count < 20:
        c = c?.nextSibling
        count += 1
    if c?.nodeType is Node.ELEMENT_NODE:
        return c

def has_start_text(elem):
    # Returns true if elem has some non-whitespace text before its first child
    # element
    for c in elem.childNodes:
        if c.nodeType is not Node.TEXT_NODE:
            break
        if c.nodeType is Node.TEXT_NODE and c.nodeValue and /\S/.test(c.nodeValue):
            return True
    return False

def handle_rtl_body(body_style):
    # Make the body and root nodes have direction ltr so that column layout
    # works as expected
    if body_style.direction is "rtl":
        for node in document.body.childNodes:
            if node.nodeType is Node.ELEMENT_NODE and window.getComputedStyle(node).direction is "rtl":
                node.style.setProperty("direction", "rtl")
        document.body.style.direction = "ltr"
        document.documentElement.style.direction = 'ltr'

def create_page_div(elem):
    div = E('blank-page-div', ' \n    ')
    document.body.appendChild(div)
    set_css(div, break_before='always', display='block', white_space='pre', background_color='transparent',
            background_image='none', border_width='0', float='none', position='static')

_in_paged_mode = False
def in_paged_mode():
    return _in_paged_mode
col_width = screen_width = screen_height = cols_per_screen = gap = col_and_gap = number_of_cols = 0
is_full_screen_layout = False

def reset_paged_mode_globals():
    nonlocal _in_paged_mode, col_width, col_and_gap, screen_height, gap, screen_width, is_full_screen_layout, cols_per_screen, number_of_cols
    scroll_viewport.reset_globals()
    col_width = screen_width = screen_height = cols_per_screen = gap = col_and_gap = number_of_cols = 0
    is_full_screen_layout = _in_paged_mode = False

def column_at(xpos):
    # Return the (zero-based) number of the column that contains xpos
    sw = scroll_viewport.paged_content_width()
    if xpos >= sw - col_and_gap:
        xpos = sw - col_width + 10
    return (xpos + gap) // col_and_gap

def fit_images():
    # Ensure no images are wider than the available width in a column. Note
    # that this method use getBoundingClientRect() which means it will
    # force a relayout if the render tree is dirty.
    images = []
    vimages = []
    img_tags = document.getElementsByTagName('img')
    bounding_rects = v'[]'
    for img_tag in img_tags:
        bounding_rects.push(img_tag.getBoundingClientRect())
    maxh = screen_height
    for i in range(img_tags.length):
        img = img_tags[i]
        br = bounding_rects[i]
        previously_limited = get_elem_data(img, 'width-limited', False)
        data = get_elem_data(img, 'img-data', None)
        if data is None:
            data = {'left':br.left, 'right':br.right, 'height':br.height, 'display': img.style.display}
            set_elem_data(img, 'img-data', data)
        left = viewport_to_document(br.left, 0, img.ownerDocument)[0]
        col = column_at(left) * col_and_gap
        rleft = left - col
        width  = br.right - br.left
        rright = rleft + width
        if previously_limited or rright > col_width:
            images.push([img, col_width - rleft])
        previously_limited = get_elem_data(img, 'height-limited', False)
        if previously_limited or br.height > maxh:
            vimages.push(img)
        if previously_limited:
            set_css(img, break_before='auto', display=data.display)
        set_css(img, break_inside='avoid')

    for img_tag, max_width in images:
        img_tag.style.setProperty('max-width', max_width+'px')
        set_elem_data(img_tag, 'width-limited', True)

    for img_tag in vimages:
        data = get_elem_data(img_tag, 'img-data', None)
        set_css(img_tag, break_before='always', max_height=maxh+'px')
        if data.height > maxh:
            # This is needed to force the image onto a new page, without
            # it, the webkit algorithm may still decide to split the image
            # by keeping it part of its parent block
            img.style.setProperty('display', 'block')
        set_elem_data(img, 'height-limited', True)


def calc_columns_per_screen():
    cps = opts.columns_per_screen or {}
    cps = cps.landscape if scroll_viewport.width() > scroll_viewport.height() else cps.portrait
    try:
        cps = int(cps)
    except:
        cps = 0
    if not cps:
        cps = int(Math.floor(scroll_viewport.width() / 500.0))
    cps = max(1, min(cps or 1, 20))
    return cps


def layout(is_single_page):
    nonlocal _in_paged_mode, col_width, col_and_gap, screen_height, gap, screen_width, is_full_screen_layout, cols_per_screen
    body_style = window.getComputedStyle(document.body)
    first_layout = not _in_paged_mode
    cps = calc_columns_per_screen()
    if first_layout:
        handle_rtl_body(body_style)
        # Check if the current document is a full screen layout like
        # cover, if so we treat it specially.
        single_screen = (document.body.scrollHeight < scroll_viewport.height() + 75)
        first_layout = True
        has_svg = document.getElementsByTagName('svg').length > 0
        imgs = document.getElementsByTagName('img')
        only_img = imgs.length is 1 and document.getElementsByTagName('div').length < 3 and document.getElementsByTagName('p').length < 2
        if only_img and window.getComputedStyle(imgs[0]).zIndex < 0:
            # Needed for some stupidly coded fixed layout EPUB comics, see for
            # instance: https://bugs.launchpad.net/calibre/+bug/1667357
            imgs[0].style.zIndex = '0'
        if not single_screen and cps > 1:
            num = cps - 1
            elems = document.querySelectorAll('body > *')
            if elems.length == 1:
                # Workaround for the case when the content is wrapped in a
                # 100% height <div>. This causes the generated page divs to
                # not be in the correct location, at least in WebKit. See
                # https://bugs.launchpad.net/bugs/1594657 for an example.
                elems[0].style.height = 'auto'
            while num > 0:
                num -= 1
                create_page_div()

    n = cols_per_screen = cps
    # Calculate the column width so that cols_per_screen columns fit exactly in
    # the window width, with their separator margins
    ww = col_width = screen_width = scroll_viewport.width()
    gap = 0
    if n > 1:
        # Adjust the side margin so that the window width satisfies
        # col_width * n + (n-1) * 2 * side_margin = window_width
        sm = opts.margin_left + opts.margin_right
        gap = sm + ((ww + sm) % n)  # Ensure ww + gap is a multiple of n
        col_width = ((ww + gap) // n) - gap

    screen_height = scroll_viewport.height()
    col_and_gap = col_width + gap

    set_css(document.body, column_gap=gap + 'px', column_width=col_width + 'px', column_rule='0px inset blue',
        min_width='0', max_width='none', min_height='0', max_height='100vh', column_fill='auto',
        margin='0', border_width='0', padding='0', box_sizing='content-box',
        width=screen_width + 'px', height=screen_height + 'px'
    )
    # Without this, webkit bleeds the margin of the first block(s) of body
    # above the columns, which causes them to effectively be added to the
    # page margins (the margin collapse algorithm)
    document.body.style.setProperty('-webkit-margin-collapse', 'separate')
    c = first_child(document.body)
    if c:
        # Remove page breaks on the first few elements to prevent blank pages
        # at the start of a chapter
        set_css(c, break_before='avoid')
        if c.tagName.toLowerCase() is 'div':
            c2 = first_child(c)
            if c2 and not has_start_text(c):
                # Common pattern of all content being enclosed in a wrapper
                # <div>, see for example: https://bugs.launchpad.net/bugs/1366074
                # In this case, we also modify the first child of the div
                # as long as there was no text before it.
                set_css(c2, break_before='avoid')

    if first_layout:
        # Because of a bug in webkit column mode, svg elements defined with
        # width 100% are wider than body and lead to a blank page after the
        # current page (when cols_per_screen == 1). Similarly img elements
        # with height=100% overflow the first column
        is_full_screen_layout = (only_img or has_svg) and single_screen and (scroll_viewport.paged_content_width() < 2*ww + 10)
        if is_single_page:
            is_full_screen_layout = True

    # Some browser engine, WebKit at least, adjust column widths to please
    # themselves, unless the container width is an exact multiple, so we check
    # for that and manually set the container widths.
    def check_column_widths():
        nonlocal number_of_cols
        ncols = number_of_cols = (scroll_viewport.paged_content_width() + gap) / col_and_gap
        if ncols is not Math.floor(ncols):
            n = number_of_cols = Math.floor(ncols)
            dw = n*col_width + (n-1)*gap
            data = {'col_width':col_width, 'gap':gap, 'scrollWidth':scroll_viewport.paged_content_width(), 'ncols':ncols, 'desired_width':dw}
            return data

    data = check_column_widths()
    if data:
        dw = data.desired_width
        for elem in document.documentElement, document.body:
            set_css(elem, max_width=dw + 'px', min_width=dw + 'px')
    data = check_column_widths()
    if data:
        print('WARNING: column layout broken, probably because there is some non-reflowable content in the book that is wider than the column width', data)

    _in_paged_mode = True
    fit_images()
    return gap

def current_scroll_offset():
    return scroll_viewport.x()


def scroll_to_offset(x):
    scroll_viewport.scroll_to(x, 0)


def scroll_to_column(number, notify=False, duration=1000):
    pos = number * col_and_gap
    limit = scroll_viewport.paged_content_width() - screen_width
    pos = min(pos, limit)
    scroll_to_offset(pos)

def scroll_to_xpos(xpos, notify=False, duration=1000):
    # Scroll so that the column containing xpos is the left most column in
    # the viewport
    if jstype(xpos) is not 'number':
        print(xpos, 'is not a number, cannot scroll to it!')
        return
    if is_full_screen_layout:
        scroll_to_offset(0)
        return
    scroll_to_column(column_at(xpos), notify=notify, duration=duration)

def scroll_to_fraction(frac):
    # Scroll to the position represented by frac (number between 0 and 1)
    xpos = Math.floor(scroll_viewport.paged_content_width() * frac)
    scroll_to_xpos(xpos)


def column_boundaries():
    # Return the column numbers at the left edge and after the right edge
    # of the viewport
    l = column_at(current_scroll_offset() + 10)
    return l, l + cols_per_screen

def current_column_location():
    # The location of the left edge of the left most column currently
    # visible in the viewport
    if is_full_screen_layout:
        return 0
    c = column_at(current_scroll_offset() + 10)
    return c * col_and_gap

def next_screen_location():
    # The position to scroll to for the next screen (which could contain
    # more than one pages). Returns -1 if no further scrolling is possible.
    if is_full_screen_layout:
        return -1
    cc = current_column_location()
    ans = cc + screen_width
    if cols_per_screen > 1:
        current_col = column_at(current_scroll_offset() + 10)
        ncols = (scroll_viewport.paged_content_width() + gap) // col_and_gap
        cols_left = ncols - (current_col + cols_per_screen)
        if cols_left < cols_per_screen:
            return -1  # Only blank, dummy pages left
    limit = scroll_viewport.paged_content_width() - scroll_viewport.width()
    if limit < col_and_gap:
        return -1
    if ans > limit:
        ans = limit if current_scroll_offset() < limit else -1
    return ans

def previous_screen_location():
    # The position to scroll to for the previous screen (which could contain
    # more than one pages). Returns -1 if no further scrolling is possible.
    if is_full_screen_layout:
        return -1
    cc = current_column_location()
    ans = cc - screen_width
    if ans < 0:
        # We ignore small scrolls (less than 15px) when going to previous
        # screen
        ans = 0 if current_scroll_offset() > 15 else -1
    return ans

def next_col_location():
    # The position to scroll to for the next column (same as
    # next_screen_location() if columns per screen == 1). Returns -1 if no
    # further scrolling is possible.
    if is_full_screen_layout:
        return -1
    cc = current_column_location()
    ans = cc + col_and_gap
    limit = scroll_viewport.paged_content_width() - scroll_viewport.width()
    if ans > limit:
        ans = limit if current_scroll_offset() < limit else -1
    return ans

def previous_col_location():
    # The position to scroll to for the previous column (same as
    # previous_screen_location() if columns per screen == 1). Returns -1 if
    # no further scrolling is possible.
    if is_full_screen_layout:
        return -1
    cc = current_column_location()
    ans = cc - col_and_gap
    if ans < 0:
        ans = 0 if current_scroll_offset() > 0 else -1
    return ans

def jump_to_anchor(name):
    # Jump to the element identified by anchor name. Ensures that the left
    # most column in the viewport is the column containing the start of the
    # element and that the scroll position is at the start of the column.
    elem = document.getElementById(name)
    if not elem:
        elems = document.getElementsByName(name)
        if elems:
            elem = elems[0]
    if not elem:
        return
    scroll_to_elem(elem)

def scroll_to_elem(elem):
    scroll_viewport.scroll_into_view(elem)
    scroll_viewport.reset_transforms()  # needed for viewport_to_document()

    if in_paged_mode:
        # Ensure we are scrolled to the column containing elem

        # Because of a bug in WebKit's getBoundingClientRect() in column
        # mode, this position can be inaccurate, see
        # https://bugs.launchpad.net/calibre/+bug/1132641 for a test case.
        # The usual symptom of the inaccuracy is br.top is highly negative.
        br = elem.getBoundingClientRect()
        if br.top < -100:
            # This only works because of the preceding call to
            # elem.scrollIntoView(). However, in some cases it gives
            # inaccurate results, so we prefer the bounding client rect,
            # when possible.
            left = elem.scrollLeft
        else:
            left = br.left
        scroll_to_xpos(viewport_to_document(
            left+2, elem.scrollTop, elem.ownerDocument)[0])

def snap_to_selection():
    # Ensure that the viewport is positioned at the start of the column
    # containing the start of the current selection
    if in_paged_mode:
        scroll_viewport.reset_transforms()  # needed for viewport_to_document()
        sel = window.getSelection()
        r = sel.getRangeAt(0).getBoundingClientRect()
        node = sel.anchorNode
        left = viewport_to_document(r.left, r.top, doc=node.ownerDocument)[0]

        # Ensure we are scrolled to the column containing the start of the
        # selection
        scroll_to_xpos(left+5)

def jump_to_cfi(cfi):
    # Jump to the position indicated by the specified conformal fragment
    # indicator. When in paged mode, the
    # scroll is performed so that the column containing the position
    # pointed to by the cfi is the left most column in the viewport
    cfi_scroll_to(cfi, def(x, y):
        if in_paged_mode:
            scroll_to_xpos(x)
        else:
            scroll_viewport.scroll_to(0, y)
    )

def current_cfi():
    # The Conformal Fragment Identifier at the current position, returns
    # null if it could not be calculated.
    ans = None
    if in_paged_mode:
        c = current_column_location()
        for x in c, c - col_and_gap, c + col_and_gap:
            # Try the current column, the previous column and the next
            # column. Each column is tried from top to bottom.
            left, right = x, x + col_and_gap
            if left < 0 or right > scroll_viewport.paged_content_width():
                continue
            deltax = col_and_gap // 25
            deltay = scroll_viewport.height() // 25
            cury = 0
            while cury < scroll_viewport.height():
                curx = left
                while curx < right - gap:
                    cfi = cfi_at_point(curx-current_scroll_offset(), cury-window.pageYOffset)
                    if cfi:
                        # print('Viewport cfi:', cfi)
                        return cfi
                    curx += deltax
                cury += deltay
    else:
        try:
            ans = cfi_at_current() or None
        except:
            traceback.print_exc()
    # if ans:
    #     print('Viewport cfi:', ans)
    return ans


def progress_frac(frac):
    # The current scroll position as a fraction between 0 and 1
    if in_paged_mode:
        limit = scroll_viewport.paged_content_width() - scroll_viewport.width()
        if limit <= 0:
            return 0.0
        return current_scroll_offset() / limit
    limit = document.body.scrollHeight - scroll_viewport.height()
    if limit <= 0:
        return 0.0
    return window.pageYOffset / limit


def onwheel(evt):
    if evt.deltaY:
        backward = evt.deltaY < 0
        x = previous_col_location() if backward else next_col_location()
        if x is -1:
            get_boss().send_message('next_spine_item', previous=backward)
        else:
            scroll_to_xpos(x)

def scroll_by_page(backward, by_screen):
    if by_screen:
        pos = previous_screen_location() if backward else next_screen_location()
        pages = cols_per_screen
    else:
        pos = previous_col_location() if backward else next_col_location()
        pages = 1
    if pos is -1:
        # dont report human scroll since we dont know if a full page was
        # scrolled or not
        get_boss().send_message('next_spine_item', previous=backward)
    else:
        if not backward:
            scrolled_frac = (pages / number_of_cols) if number_of_cols > 0 else 0
            get_boss().report_human_scroll(scrolled_frac)
        else:
            get_boss().report_human_scroll()
        scroll_to_xpos(pos)


def handle_shortcut(sc_name, evt):
    if sc_name is 'up':
        scroll_by_page(True, True)
        return True
    if sc_name is 'down':
        scroll_by_page(False, True)
        return True
    if sc_name is 'start_of_file':
        get_boss().report_human_scroll()
        scroll_to_offset(0)
        return True
    if sc_name is 'end_of_file':
        get_boss().report_human_scroll()
        scroll_to_offset(document_width())
        return True
    if sc_name is 'left':
        scroll_by_page(True, False)
        return True
    if sc_name is 'right':
        scroll_by_page(False, False)
        return True
    if sc_name is 'start_of_book':
        get_boss().report_human_scroll()
        get_boss().send_message('goto_doc_boundary', start=True)
        return True
    if sc_name is 'end_of_book':
        get_boss().report_human_scroll()
        get_boss().send_message('goto_doc_boundary', start=False)
        return True
    if sc_name is 'pageup':
        scroll_by_page(True, True)
        return True
    if sc_name is 'pagedown':
        scroll_by_page(False, True)
        return True
    return False


def handle_gesture(gesture):
    if gesture.type is 'swipe':
        if gesture.axis is 'vertical':
            if not gesture.active:
                get_boss().send_message('next_section', forward=gesture.direction is 'up')
        else:
            if not gesture.active or gesture.is_held:
                scroll_by_page(gesture.direction is 'right', True)
    elif gesture.type is 'prev-page':
        scroll_by_page(True, False)
    elif gesture.type is 'next-page':
        scroll_by_page(False, False)
    elif gesture.type is 'long-tap':
        r = word_at_point(gesture.viewport_x, gesture.viewport_y)
        if r:
            s = document.getSelection()
            s.removeAllRanges()
            s.addRange(r)
            get_boss().send_message('lookup_word', word=str(r))


anchor_funcs = {
    'pos_for_elem': def pos_for_elem(elem):
        if not elem:
            return 0
        br = elem.getBoundingClientRect()
        x = viewport_to_document(br.left, br.top, elem.ownerDocument)[0]
        return column_at(x)
    ,
    'visibility': def visibility(pos):
        first = column_at(current_scroll_offset() + 10)
        if pos < first:
            return -1
        if pos < first + cols_per_screen:
            return 0
        return 1
    ,
    'cmp': def cmp(a, b):
        return a - b
    ,
}