curses_tui.py

#!/usr/bin/env python3

"""
MIT License

Copyright (c) 2018 mingrammer

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
"""
# Origin: https://github.com/mingrammer/python-curses-scroll-example/blob/master/tui.py
# Adapted for use in Jenkins Queue Checker

import curses
import curses.textpad
import signal


def alarmHandler(signum, frame):
    raise TimeoutError


class Screen(object):
    UP = -1
    DOWN = 1

    def __init__(self, items):
        """ Initialize the screen window
        Attributes
            window: A full curses screen window
            width: The width of `window`
            height: The height of `window`
            max_lines: Maximum visible line count for `result_window`
            top: Available top line position for current page (used on scrolling)
            bottom: Available bottom line position for whole pages (as length of items)
            current: Current highlighted line number (as window cursor)
            page: Total page count which being changed corresponding to result of a query (starts from 0)
            ┌--------------------------------------┐
            |1. Item                               |
            |--------------------------------------| <- top = 1
            |2. Item                               |
            |3. Item                               |
            |4./Item///////////////////////////////| <- current = 3
            |5. Item                               |
            |6. Item                               |
            |7. Item                               |
            |8. Item                               | <- max_lines = 7
            |--------------------------------------|
            |9. Item                               |
            |10. Item                              | <- bottom = 10
            |                                      |
            |                                      | <- page = 1 (0 and 1)
            └--------------------------------------┘
        Returns
            None
        """
        self.window = None

        self.width = 0
        self.height = 0

        self.init_curses()

        self.items = items

        self.max_lines = curses.LINES
        self.top = 0
        self.bottom = len(self.items)
        self.current = 0
        self.page = self.bottom // self.max_lines

        # self.run()

    def init_curses(self):
        """Setup the curses"""
        self.window = curses.initscr()
        self.window.keypad(True)

        curses.noecho()
        curses.cbreak()

        curses.start_color()
        curses.init_pair(1, curses.COLOR_CYAN, curses.COLOR_BLACK)
        curses.init_pair(2, curses.COLOR_BLACK, curses.COLOR_CYAN)

        self.current = curses.color_pair(2)

        self.height, self.width = self.window.getmaxyx()

    def run(self):
        """Continue running the TUI until get interrupted"""
        try:
            self.input_stream()
        except KeyboardInterrupt:
            pass
        finally:
            curses.endwin()

    def input_stream(self):
        """Waiting an input and run a proper method according to type of input"""
        while True:
            self.refresh_items()
            self.display()

            ch = self.window.getch()
            if ch == curses.KEY_UP:
                self.scroll(self.UP)
            elif ch == curses.KEY_DOWN:
                self.scroll(self.DOWN)
            elif ch == curses.KEY_LEFT:
                self.paging(self.UP)
            elif ch == curses.KEY_RIGHT:
                self.paging(self.DOWN)
            elif ch == curses.ascii.ESC:
                break

    def input_stream_no_loop(self, timeout):
        self.display()
        signal.signal(signal.SIGALRM, alarmHandler)
        signal.alarm(timeout)
        try:
            ch = self.window.getch()
            if ch == curses.KEY_UP:
                self.scroll(self.UP)
            elif ch == curses.KEY_DOWN:
                self.scroll(self.DOWN)
            elif ch == curses.KEY_LEFT:
                self.paging(self.UP)
            elif ch == curses.KEY_RIGHT:
                self.paging(self.DOWN)
            elif ch == curses.ascii.ESC:
                curses.endwin()
            signal.alarm(0)
            pass
        except TimeoutError:
            # Timeout
            signal.alarm(0)
            pass
        signal.signal(signal.SIGALRM, signal.SIG_IGN)
        return

    def scroll(self, direction):
        """Scrolling the window when pressing up/down arrow keys"""
        # next cursor position after scrolling
        next_line = self.current + direction

        # Up direction scroll overflow
        # current cursor position is 0, but top position is greater than 0
        if (direction == self.UP) and (self.top > 0 and self.current == 0):
            self.top += direction
            return
        # Down direction scroll overflow
        # next cursor position touch the max lines, but absolute position of
        # max lines could not touch the bottom
        if (direction == self.DOWN) and (next_line == self.max_lines) and (
                self.top + self.max_lines < self.bottom):
            self.top += direction
            return
        # Scroll up
        # current cursor position or top position is greater than 0
        if (direction == self.UP) and (self.top > 0 or self.current > 0):
            self.current = next_line
            return
        # Scroll down
        # next cursor position is above max lines, and absolute position of
        # next cursor could not touch the bottom
        if (direction == self.DOWN) and (next_line < self.max_lines) and (
                self.top + next_line < self.bottom):
            self.current = next_line
            return

    def paging(self, direction):
        """Paging the window when pressing left/right arrow keys"""
        current_page = (self.top + self.current) // self.max_lines
        next_page = current_page + direction
        # The last page may have fewer items than max lines,
        # so we should adjust the current cursor position as maximum item count
        # on last page
        if next_page == self.page:
            self.current = min(self.current, self.bottom % self.max_lines - 1)

        # Page up
        # if current page is not a first page, page up is possible
        # top position can not be negative, so if top position is going to be
        # negative, we should set it as 0
        if (direction == self.UP) and (current_page > 0):
            self.top = max(0, self.top - self.max_lines)
            return
        # Page down
        # if current page is not a last page, page down is possible
        if (direction == self.DOWN) and (current_page < self.page):
            self.top += self.max_lines
            return

    def display(self):
        """Display the items on window"""
        self.window.erase()
        for idx, item in enumerate(
                self.items[self.top:self.top + self.max_lines]):
            # Highlight the current cursor line
            if idx == self.current:
                self.window.addstr(idx, 0, item, curses.color_pair(2))
            else:
                self.window.addstr(idx, 0, item, curses.color_pair(1))
        self.window.refresh()

    def update_items(self, items):
        self.items = items
        self.bottom = len(items)
        self.page = self.bottom // self.max_lines