170 lines
6.3 KiB
Python
170 lines
6.3 KiB
Python
"""Integrated command-line implementation."""
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import curses
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import curses.ascii
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import curses.textpad
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from bebop.links import Links
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class CommandLine:
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"""Basic and flaky command-line à la Vim, using curses module's Textbox."""
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def __init__(self, window):
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self.window = window
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self.textbox = None
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def clear(self):
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"""Clear command-line contents."""
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self.window.clear()
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self.window.refresh()
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def focus(self, command_char, validator=None, prefix=""):
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"""Give user focus to the command bar.
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Show the command char and give focus to the command textbox. The
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validator function is passed to the textbox.
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Arguments:
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- command_char: char to display before the command line; it must be an
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str of length 1, else the return value of `gather` might be wrong.
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- validator: function to use to validate the input chars; if omitted,
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`validate_common_input` is used.
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- prefix: string to insert before the cursor in the command line.
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Returns:
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User input as string. The string will be empty if the validator raised
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an EscapeInterrupt.
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"""
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self.window.clear()
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self.window.refresh()
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self.textbox = curses.textpad.Textbox(self.window)
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self.window.addstr(command_char + prefix)
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curses.curs_set(1)
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try:
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command = self.textbox.edit(validator or self.validate_common_input)
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except EscapeCommandInterrupt:
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command = ""
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except TerminateCommandInterrupt as exc:
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command = exc.command
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else:
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command = command[1:].rstrip()
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curses.curs_set(0)
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self.clear()
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return command
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def gather(self):
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"""Return the string currently written by the user in command line."""
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return self.textbox.gather()[1:].rstrip()
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def validate_common_input(self, ch: int):
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"""Generic input validator, handles a few more cases than default.
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This validator can be used as a default validator as it handles, on top
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of the Textbox defaults:
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- Erasing the first command char, i.e. clearing the line, cancels the
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command input.
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- Pressing ESC also cancels the input.
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This validator can be safely called at the beginning of other validators
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to handle the keys above.
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"""
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if ch == curses.KEY_BACKSPACE: # Cancel input if all line is cleaned.
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text = self.gather()
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if len(text) == 0:
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raise EscapeCommandInterrupt()
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elif ch == curses.ascii.ESC: # Could be ESC or ALT
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self.window.nodelay(True)
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ch = self.window.getch()
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if ch == -1:
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raise EscapeCommandInterrupt()
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self.window.nodelay(False)
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return ch
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def focus_for_link_navigation(self, init_char: int, links: Links):
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"""Handle a initial digit input by the user.
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When a digit key is pressed, the user intents to visit a link (or
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dropped something on the numpad). To reduce the number of key types
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needed, Bebop uses the following algorithm:
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- If the current user input identifies a link without ambiguity, it is
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used directly.
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- If it is ambiguous, the user either inputs as many digits required
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to disambiguate the link ID, or press enter to validate her input.
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Examples:
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- I have 3 links. Pressing "2" takes me to link 2.
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- I have 15 links. Pressing "3" takes me to link 3 (no ambiguity).
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- I have 15 links. Pressing "1" and "2" takes me to link 12.
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- I have 456 links. Pressing "1", "2" and Enter takes me to link 12.
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- I have 456 links. Pressing "1", "2" and "6" takes me to link 126.
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Arguments:
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- init_char: the first char (code) being pressed.
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- links: accessible Links.
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Returns:
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The tuple (error, value); if error is 0, value is the link ID to use; if
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error is 1, discard value and do nothing; if error is 2, value is an
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error than can be showed to the user.
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"""
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digit = init_char & 0xf
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num_links = len(links)
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# If there are less than 10 links, just open it now.
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if num_links < 10:
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return 0, digit
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# Else check if the digit alone is sufficient.
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digit = chr(init_char)
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max_digits = 0
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while num_links:
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max_digits += 1
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num_links //= 10
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candidates = links.disambiguate(digit, max_digits)
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if len(candidates) == 1:
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return 0, candidates[0]
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# Else, focus the command line to let the user input more digits.
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validator = lambda ch: self.validate_link_digit(ch, links, max_digits)
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link_input = self.focus("&", validator, digit)
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if not link_input:
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return 1, None
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try:
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link_id = int(link_input)
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except ValueError:
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return 2, f"Invalid link ID {link_input}."
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return 0, link_id
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def validate_link_digit(self, ch: int, links: Links, max_digits: int):
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"""Handle input chars to be used as link ID."""
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# Handle common chars.
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ch = self.validate_common_input(ch)
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# Only accept digits. If we reach the amount of required digits, open
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# link now and leave command line. Else just process it.
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if curses.ascii.isdigit(ch):
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digits = self.gather() + chr(ch)
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candidates = links.disambiguate(digits, max_digits)
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if len(candidates) == 1:
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raise TerminateCommandInterrupt(candidates[0])
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return ch
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# If not a digit but a printable character, ignore it.
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if curses.ascii.isprint(ch):
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return 0
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# Everything else could be a control character and should be processed.
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return ch
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class EscapeCommandInterrupt(Exception):
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"""Signal that ESC has been pressed during command line."""
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pass
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class TerminateCommandInterrupt(Exception):
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"""Signal that validation ended command line input early.
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The value to use is stored in the command attribute. This value can be of
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any type: str for common commands but also int for ID input, etc.
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"""
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def __init__(self, command, *args, **kwargs):
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super().__init__(*args, **kwargs)
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self.command = command
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