Bebop/bebop/browser/browser.py

"""Main browser logic."""

import curses
import curses.ascii
import curses.textpad
import os
import tempfile
from math import inf

from bebop.bookmarks import (
    get_bookmarks_path, get_bookmarks_document, save_bookmark
)
from bebop.colors import ColorPair, init_colors
from bebop.command_line import CommandLine
from bebop.external import open_external_program
from bebop.help import HELP_PAGE
from bebop.history import History
from bebop.links import Links
from bebop.mouse import ButtonState
from bebop.navigation import (
    get_parent_url, get_root_url, join_url, parse_url, sanitize_url)
from bebop.page import Page
from bebop.page_pad import PagePad


class Browser:
    """Manage the events, inputs and rendering.

    Attributes:
    - config: config dict passed to the browser.
    - stash: certificate stash passed to the browser.
    - screen: curses stdscr.
    - dim: current screen dimensions.
    - page_pad: curses pad containing the current page view.
    - status_line: curses window used to report current status.
    - command_line: a CommandLine object for the user to interact with.
    - running: the browser will continue running while this is true.
    - status_data: 3-uple of status text, color pair and attributes of the
      status line, used to reset status after an error.
    - history: an History object.
    - cache: a dict containing cached pages
    - special_pages: a dict containing page names used with "bebop" scheme;
      values are dicts as well: the "open" key maps to a callable to use when
      the page is accessed, and the optional "source" key maps to callable
      returning the page source path.
    """

    def __init__(self, config, cert_stash):
        self.config = config
        self.stash = cert_stash or {}
        self.screen = None
        self.dim = (0, 0)
        self.page_pad = None
        self.status_line = None
        self.command_line = None
        self.running = True
        self.status_data = ("", 0, 0)
        self.history = History()
        self.cache = {}
        self.special_pages = self.setup_special_pages()
        self._current_url = ""

    @property
    def h(self):
        return self.dim[0]

    @property
    def w(self):
        return self.dim[1]

    @property
    def current_url(self):
        """Return the current URL."""
        return self._current_url

    @current_url.setter
    def current_url(self, url):
        """Set the current URL and show it in the status line."""
        self._current_url = url
        self.set_status(url)

    def setup_special_pages(self):
        """Return a dict with the special pages functions."""
        return {
            "bookmarks": {
                "open": self.open_bookmarks,
                "source": lambda: str(get_bookmarks_path())
            },
            "help": {
                "open": self.open_help,
            },
        }

    def run(self, *args, **kwargs):
        """Use curses' wrapper around _run."""
        os.environ.setdefault("ESCDELAY", "25")
        curses.wrapper(self._run, *args, **kwargs)

    def _run(self, stdscr, start_url=None):
        """Start displaying content and handling events."""
        self.screen = stdscr
        self.screen.clear()
        self.screen.refresh()

        curses.mousemask(curses.ALL_MOUSE_EVENTS)
        curses.curs_set(0)
        init_colors()

        self.dim = self.screen.getmaxyx()
        self.page_pad = PagePad(self.h - 2)
        self.status_line = self.screen.subwin(
            *self.line_dim,
            *self.status_line_pos,
        )
        command_line_window = self.screen.subwin(
            *self.line_dim,
            *self.command_line_pos,
        )
        self.command_line = CommandLine(
            command_line_window,
            self.config["command_editor"]
        )

        if start_url:
            self.open_url(start_url, assume_absolute=True)

        while self.running:
            try:
                self.handle_inputs()
            except KeyboardInterrupt:
                self.set_status("Cancelled.")

    def handle_inputs(self):
        char = self.screen.getch()
        if char == ord("?"):
            self.open_help()
        elif char == ord(":"):
            self.quick_command("")
        elif char == ord("r"):
            self.reload_page()
        elif char == ord("h"):
            self.scroll_page_horizontally(-3)
        elif char == ord("H"):
            self.scroll_whole_page_left()
        elif char == ord("j"):
            self.scroll_page_vertically(3)
        elif char == ord("J"):
            self.scroll_whole_page_down()
        elif char == ord("k"):
            self.scroll_page_vertically(-3)
        elif char == ord("K"):
            self.scroll_whole_page_up()
        elif char == ord("l"):
            self.scroll_page_horizontally(3)
        elif char == ord("L"):
            self.scroll_whole_page_right()
        elif char == ord("^"):
            self.scroll_page_horizontally(-inf)
        elif char == ord("g"):
            char = self.screen.getch()
            if char == ord("g"):
                self.scroll_page_vertically(-inf)
        elif char == ord("G"):
            self.scroll_page_vertically(inf)
        elif char == ord("o"):
            self.quick_command("open")
        elif char == ord("p"):
            self.go_back()
        elif char == ord("u"):
            self.go_to_parent_page()
        elif char == ord("U"):
            self.go_to_root_page()
        elif char == ord("b"):
            self.open_bookmarks()
        elif char == ord("B"):
            self.add_bookmark()
        elif char == ord("e"):
            self.edit_page()
        elif curses.ascii.isdigit(char):
            self.handle_digit_input(char)
        elif char == curses.KEY_MOUSE:
            self.handle_mouse(*curses.getmouse())
        elif char == curses.KEY_RESIZE:
            self.handle_resize()
        elif char == curses.ascii.ESC:  # Can be ESC or ALT char.
            self.screen.nodelay(True)
            char = self.screen.getch()
            if char == -1:
                self.reset_status()
            else:  # ALT keybinds.
                if char == ord("h"):
                    self.scroll_page_horizontally(-1)
                elif char == ord("j"):
                    self.scroll_page_vertically(1)
                elif char == ord("k"):
                    self.scroll_page_vertically(-1)
                elif char == ord("l"):
                    self.scroll_page_horizontally(1)
            self.screen.nodelay(False)
        # else:
        #     unctrled = curses.unctrl(char)
        #     if unctrled == b"^T":
        #         self.set_status("test!")

    @property
    def page_pad_size(self):
        return self.h - 3, self.w - 1

    @property
    def status_line_pos(self):
        return self.h - 2, 0

    @property
    def command_line_pos(self):
        return self.h - 1, 0

    @property
    def line_dim(self):
        return 1, self.w

    def refresh_windows(self):
        """Refresh all windows and clear command line."""
        self.refresh_page()
        self.refresh_status_line()
        self.command_line.clear()

    def refresh_page(self):
        """Refresh the current page pad; it does not reload the page."""
        self.page_pad.refresh_content(*self.page_pad_size)

    def refresh_status_line(self):
        """Refresh status line contents."""
        text, pair, attributes = self.status_data
        text = text[:self.w - 1]
        color = curses.color_pair(pair)
        self.status_line.addstr(0, 0, text, color | attributes)
        self.status_line.clrtoeol()
        self.status_line.refresh()

    def set_status(self, text):
        """Set a regular message in the status bar."""
        self.status_data = text, ColorPair.NORMAL, curses.A_ITALIC
        self.refresh_status_line()

    def reset_status(self):
        """Reset status line, e.g. after a cancelled action."""
        self.set_status(self.current_url)

    def set_status_error(self, text):
        """Set an error message in the status bar."""
        self.status_data = text, ColorPair.ERROR, 0
        self.refresh_status_line()

    def quick_command(self, command):
        """Shortcut method to take user input with a prefixed command string."""
        prefix = command + " " if command else ""
        text = self.command_line.focus(CommandLine.CHAR_COMMAND, prefix=prefix)
        if not text:
            return
        self.process_command(text)

    def process_command(self, command_text: str):
        """Handle a client command."""
        words = command_text.split()
        num_words = len(words)
        if num_words == 0:
            return
        command = words[0]
        if num_words == 1:
            if command in ("q", "quit"):
                self.running = False
            return
        if command in ("o", "open"):
            self.open_url(words[1], assume_absolute=True)

    def open_url(self, url, base_url=None, redirects=0, assume_absolute=False,
                 history=True, use_cache=True):
        """Try to open an URL.

        This function assumes that the URL can be from an user and thus tries a
        few things to make it work.

        If there is no current URL (e.g. we just started) or `assume_absolute`
        is True, assume it is an absolute URL. In other cases, parse it normally
        and later check if it has to be used relatively to the current URL.
        
        Arguments:
        - url: an URL string, may not be completely compliant.
        - base_url: an URL string to use as base in case `url` is relative.
        - redirections: number of redirections we did yet for the same request.
        - assume_absolute: assume we intended to use an absolute URL if True.
        - history: whether the URL should be pushed to history on success.
        - use_cache: whether we should look for an already cached document.
        """
        if redirects > 5:
            self.set_status_error(f"Too many redirections ({url}).")
            return

        if assume_absolute or not self.current_url:
            parts = parse_url(url, absolute=True)
            join = False
        else:
            parts = parse_url(url)
            join = True

        if parts.scheme == "gemini":
            from bebop.browser.gemini import open_gemini_url
            # If there is no netloc, this is a relative URL.
            if join or base_url:
                url = join_url(base_url or self.current_url, url)
            open_gemini_url(
                self,
                sanitize_url(url),
                redirects=redirects,
                history=history,
                use_cache=use_cache
            )
        elif parts.scheme.startswith("http"):
            from bebop.browser.web import open_web_url
            open_web_url(self, url)
        elif parts.scheme == "file":
            from bebop.browser.file import open_file
            open_file(self, parts.path, history=history)
        elif parts.scheme == "bebop":
            special_page = self.special_pages.get(parts.netloc)
            if special_page:
                special_page["open"]()
            else:
                self.set_status_error("Unknown page.")
        else:
            self.set_status_error(f"Protocol {parts.scheme} not supported.")

    def load_page(self, page: Page):
        """Load Gemtext data as the current page."""
        old_pad_height = self.page_pad.dim[0]
        self.page_pad.show_page(page)
        if self.page_pad.dim[0] < old_pad_height:
            self.screen.clear()
            self.screen.refresh()
            self.refresh_windows()
        else:
            self.refresh_page()

    def handle_digit_input(self, init_char: int):
        """Focus command-line to select the link ID to follow."""
        if self.page_pad.current_page is None:
            return
        links = self.page_pad.current_page.links
        if links is None:
            return
        err, val = self.command_line.focus_for_link_navigation(init_char, links)
        if err == 0:
            self.open_link(links, val)  # type: ignore
        elif err == 2:
            self.set_status_error(val)

    def open_link(self, links: Links, link_id: int):
        """Open the link with this link ID."""
        if not link_id in links:
            self.set_status_error(f"Unknown link ID {link_id}.")
            return
        self.open_url(links[link_id])

    def handle_mouse(self, mouse_id: int, x: int, y: int, z: int, bstate: int):
        """Handle mouse events.

        Right now, only vertical scrolling is handled.
        """
        if bstate & ButtonState.SCROLL_UP:
            self.scroll_page_vertically(-3)
        elif bstate & ButtonState.SCROLL_DOWN:
            self.scroll_page_vertically(3)

    def handle_resize(self):
        """Try to not make everything collapse on resizes."""
        # Refresh the whole screen before changing windows to avoid random
        # blank screens.
        self.screen.refresh()
        old_dim = self.dim
        self.dim = self.screen.getmaxyx()
        # Avoid work if the resizing does not impact us.
        if self.dim == old_dim:
            return
        # Resize windows to fit the new dimensions. Content pad will be updated
        # on its own at the end of the function.
        self.status_line.resize(*self.line_dim)
        self.command_line.window.resize(*self.line_dim)
        # Move the windows to their new position if that's still possible.
        if self.status_line_pos[0] >= 0:
            self.status_line.mvwin(*self.status_line_pos)
        if self.command_line_pos[0] >= 0:
            self.command_line.window.mvwin(*self.command_line_pos)
        # If the content pad does not fit its whole place, we have to clean the
        # gap between it and the status line. Refresh all screen.
        if self.page_pad.dim[0] < self.h - 2:
            self.screen.clear()
            self.screen.refresh()
        self.refresh_windows()

    def scroll_page_vertically(self, by_lines):
        """Scroll page vertically.

        If `by_lines` is an integer (positive or negative), scroll the page by
        this amount of lines. If `by_lines` is one of the floats inf and -inf,
        go to the end of file and beginning of file, respectively.
        """
        window_height = self.h - 2
        require_refresh = False
        if by_lines == inf:
            require_refresh = self.page_pad.go_to_end(window_height)
        elif by_lines == -inf:
            require_refresh = self.page_pad.go_to_beginning()
        else:
            require_refresh = self.page_pad.scroll_v(by_lines, window_height)
        if require_refresh:
            self.refresh_page()

    def scroll_whole_page_down(self):
        """Scroll down by a whole page."""
        self.scroll_page_vertically(self.page_pad_size[0])

    def scroll_whole_page_up(self):
        """Scroll up by a whole page."""
        self.scroll_page_vertically(-self.page_pad_size[0])

    def scroll_page_horizontally(self, by_columns):
        """Scroll page horizontally.

        If `by_lines` is an integer (positive or negative), scroll the page by
        this amount of columns. If `by_lines` is -inf, scroll back to the first
        column. Scrolling to the right-most column is not supported.
        """
        if by_columns == -inf:
            require_refresh = self.page_pad.go_to_first_column()
        else:
            require_refresh = self.page_pad.scroll_h(by_columns, self.w)
        if require_refresh:
            self.refresh_page()

    def scroll_whole_page_left(self):
        """Scroll left by a whole page."""
        self.scroll_page_horizontally(-self.page_pad_size[1])

    def scroll_whole_page_right(self):
        """Scroll right by a whole page."""
        self.scroll_page_horizontally(self.page_pad_size[1])

    def reload_page(self):
        """Reload the page, if one has been previously loaded."""
        if self.current_url:
            self.open_url(self.current_url, history=False, use_cache=False)

    def go_back(self):
        """Go back in history if possible."""
        if self.history.has_links():
            self.open_url(self.history.pop(), history=False)

    def go_to_parent_page(self):
        """Go to the parent URL if possible."""
        if self.current_url:
            self.open_url(get_parent_url(self.current_url))

    def go_to_root_page(self):
        """Go to the root URL if possible."""
        if self.current_url:
            self.open_url(get_root_url(self.current_url))

    def open_bookmarks(self):
        """Open bookmarks."""
        content = get_bookmarks_document()
        if content is None:
            self.set_status_error("Failed to open bookmarks.")
            return
        self.load_page(Page.from_gemtext(content, self.config["text_width"]))
        self.current_url = "bebop://bookmarks"

    def add_bookmark(self):
        """Add the current URL as bookmark."""
        if not self.current_url:
            return
        self.set_status("Bookmark title?")
        current_title = self.page_pad.current_page.title or ""
        title = self.command_line.focus(
            CommandLine.CHAR_TEXT,
            prefix=current_title
        )
        if title:
            title = title.strip()
            if title:
                save_bookmark(self.current_url, title)
        self.reset_status()

    def edit_page(self):
        """Open a text editor to edit the page source.

        For external pages, the source is written in a temporary file, opened in
        its editor of choice and so it's up to the user to save it where she
        needs it, if needed. Internal pages, e.g. the bookmarks page, are loaded
        directly from their location on disk.
        """
        delete_source_after = False
        if self.current_url.startswith("bebop://"):
            page_name = self.current_url[len("bebop://"):]
            special_pages_functions = self.special_pages.get(page_name)
            if not special_pages_functions:
                return
            get_source = special_pages_functions.get("source")
            source_filename = get_source() if get_source else None
        else:
            if not self.page_pad.current_page:
                return
            source = self.page_pad.current_page.source
            with tempfile.NamedTemporaryFile("wt", delete=False) as source_file:
                source_file.write(source)
                source_filename = source_file.name
            delete_source_after = True

        if not source_filename:
            return

        command = self.config["source_editor"] + [source_filename]
        open_external_program(command)
        if delete_source_after:
            os.unlink(source_filename)
        self.refresh_windows()

    def open_help(self):
        """Show the help page."""
        self.load_page(Page.from_gemtext(HELP_PAGE, self.config["text_width"]))
        self.current_url = "bebop://help"

    def prompt(self, text, keys):
        """Display the text and allow it to type one of the given keys."""
        self.set_status(text)
        return self.command_line.prompt_key(keys)