From f28da2648c0556e9f8d9e89d22d0e5b27ac946e2 Mon Sep 17 00:00:00 2001
From: Michael Lazar <lazar.michael22@gmail.com>
Date: Sun, 25 Jan 2015 01:50:18 -0800
Subject: [PATCH] Viewer abstracted out, cursor now detects out of bounds.

---
 rtv/content_generators.py |  15 ++--
 rtv/subreddit.py          | 147 ++++++++++----------------------------
 rtv/viewer.py             | 115 +++++++++++++++++++++++++++++
 3 files changed, 165 insertions(+), 112 deletions(-)
 create mode 100644 rtv/viewer.py

diff --git a/rtv/content_generators.py b/rtv/content_generators.py
index 828b4d5..56b0347 100644
--- a/rtv/content_generators.py
+++ b/rtv/content_generators.py
@@ -121,17 +121,24 @@ class SubredditGenerator(object):
 
         return data
 
-    def get(self, index, n_cols):
+    def get(self, index, n_cols=70):
         """
         Grab the `i`th submission, with the title field formatted to fit inside
         of a window of width `n`
         """
 
-        assert(index >= 0)
+        if index < 0:
+            raise IndexError
 
         while index >= len(self._submission_data):
-            data = self.strip_praw_submission(self._submissions.next())
-            self._submission_data.append(data)
+
+            try:
+                submission = self._submissions.next()
+            except StopIteration:
+                raise IndexError
+            else:
+                data = self.strip_praw_submission(submission)
+                self._submission_data.append(data)
 
         # Modifies the original dict, faster than copying
         data = self._submission_data[index]
diff --git a/rtv/subreddit.py b/rtv/subreddit.py
index e74c58d..70f2585 100644
--- a/rtv/subreddit.py
+++ b/rtv/subreddit.py
@@ -4,44 +4,36 @@ import curses
 
 from content_generators import SubredditGenerator
 from utils import curses_session
+from viewer import BaseViewer
 
-class SubredditViewer(object):
+class SubredditViewer(BaseViewer):
 
-    def __init__(self, stdscr, subreddit_generator):
+    def __init__(self, stdscr, subreddit_content):
 
         self.stdscr = stdscr
-        self.gen = subreddit_generator
 
-        self._cursor_index = 0
-        self._page_index = 0
-        self._rows = None
-        self._cols = None
+        self._n_rows = None
+        self._n_cols = None
         self._title_window = None
         self._content_window = None
-        self._sub_windows = []
-        self._direction = True
-        self._window_is_partial = None
+        self._sub_windows = None
 
+        super(SubredditViewer, self).__init__(subreddit_content)
         self.draw()
 
-    def loop(self):
+    @property
+    def n_subwindows(self):
+        return len(self._sub_windows)
 
+    def loop(self):
         while True:
             cmd = self.stdscr.getch()
 
-            # Move cursor up one submission
             if cmd == curses.KEY_UP:
-                if self._direction:
-                    self.move_cursor_backward()
-                else:
-                    self.move_cursor_forward()
+                self.move_cursor_up()
 
-            # Move cursor down one submission
             elif cmd == curses.KEY_DOWN:
-                if self._direction:
-                    self.move_cursor_forward()
-                else:
-                    self.move_cursor_backward()
+                self.move_cursor_down()
 
             # View submission
             elif cmd in (curses.KEY_RIGHT, ord(' ')):
@@ -65,120 +57,60 @@ class SubredditViewer(object):
     def draw(self):
 
         # Refresh window bounds incase the screen has been resized
-        self._rows, self._cols = self.stdscr.getmaxyx()
-        self._title_window = self.stdscr.derwin(1, self._cols, 0, 0)
+        self._n_rows, self._n_cols = self.stdscr.getmaxyx()
+        self._title_window = self.stdscr.derwin(1, self._n_cols, 0, 0)
         self._content_window = self.stdscr.derwin(1, 0)
 
         self.draw_header()
         self.draw_content()
-        self.draw_cursor()
-
-    def move_cursor_forward(self):
-
-        self.remove_cursor()
-
-        last_index = len(self._sub_windows) - 1
-
-        self._cursor_index += 1
-        if self._cursor_index == last_index:
-
-            if self._direction:
-                self._page_index = self._page_index + self._cursor_index
-                self._cursor_index = 0
-                self._direction = False
-            else:
-                self._page_index = self._page_index - self._cursor_index
-                self._cursor_index = 0
-                self._direction = True
-            self.draw_content()
-
-        self.draw_cursor()
-
-    def move_cursor_backward(self):
-
-        self.remove_cursor()
-
-        last_index = len(self._sub_windows) - 1
-
-        self._cursor_index -= 1
-        if self._cursor_index < 0:
-
-            if self._direction:
-                self._page_index -= 1
-                self._cursor_index = 0
-            else:
-                self._page_index += 1
-                self._cursor_index = 0
-            self.draw_content()
-
-        self.draw_cursor()
-
-    def draw_cursor(self):
-
-        window = self._sub_windows[self._cursor_index]
-        rows, _ = window.getmaxyx()
-        for row in xrange(rows):
-            window.chgat(row, 0, 1, curses.A_REVERSE)
-        window.refresh()
-
-    def remove_cursor(self):
-
-        window = self._sub_windows[self._cursor_index]
-        rows, _ = window.getmaxyx()
-        for row in xrange(rows):
-            window.chgat(row, 0, 1, curses.A_NORMAL)
-        window.refresh()
+        self.add_cursor()
 
     def draw_content(self):
         """
         Loop through submissions and fill up the content page.
         """
 
-        rows, cols = self._content_window.getmaxyx()
+        n_rows, n_cols = self._content_window.getmaxyx()
         self._content_window.erase()
         self._sub_windows = []
 
-        if self._direction:
-            row = 0
-            for data in self.gen.iterate(self._page_index, 1, cols-1):
-                available_rows = (rows - row)
-                n_rows = min(available_rows, data['n_rows'])
-                window = self._content_window.derwin(n_rows, cols, row, 0)
-                self.draw_submission(window, data, self._direction)
-                self._sub_windows.append(window)
-                row += (n_rows + 1)
-                if row >= rows:
-                    break
-        else:
-            row = rows
-            for data in self.gen.iterate(self._page_index, -1, cols-1):
-                available_rows = row
-                n_rows = min(available_rows, data['n_rows'])
-                window = self._content_window.derwin(n_rows, cols, row-n_rows, 0)
-                self.draw_submission(window, data, self._direction)
-                self._sub_windows.append(window)
-                row -= (n_rows + 1)
-                if row < 0:
-                    break
+        page_index, cursor_index, inverted = self.nav.position
+        step = self.nav.step
+
+        # If not inverted, align the first submission with the top and draw
+        # downwards. If inverted, align the first submission with the bottom
+        # and draw upwards.
+        current_row = n_rows if inverted else 0
+        available_rows = n_rows
+        for data in self.content.iterate(page_index, step, n_cols-1):
+            window_rows = min(available_rows, data['n_rows'])
+            start = current_row - window_rows if inverted else current_row
+            window = self._content_window.derwin(window_rows, n_cols, start, 0)
+            self.draw_submission(window, data, inverted)
+            self._sub_windows.append(window)
+            available_rows -= (window_rows + 1)  # Add one for the blank line
+            current_row += step * (window_rows + 1)
+            if available_rows <= 0:
+                break
 
-        self._window_is_partial = (available_rows < data['n_rows'])
         self._content_window.refresh()
 
     def draw_header(self):
 
+        sub_name = self.content.display_name
         self._title_window.erase()
-        self._title_window.addnstr(0, 0, self.gen.display_name, self._cols)
+        self._title_window.addnstr(0, 0, sub_name, self._n_cols)
         self._title_window.refresh()
 
     @staticmethod
-    def draw_submission(win, data, direction):
+    def draw_submission(win, data, inverted=False):
 
         n_rows, n_cols = win.getmaxyx()
         n_cols -= 1  # Leave space for the cursor in the first column
 
         # Handle the case where the window is not large enough to fit the data.
         valid_rows = range(0, n_rows)
-        offset = 0 if direction else -(data['n_rows'] - n_rows)
+        offset = 0 if not inverted else -(data['n_rows'] - n_rows)
 
         n_title = len(data['split_title'])
         for row, text in enumerate(data['split_title'], start=offset):
@@ -197,7 +129,6 @@ class SubredditViewer(object):
         if row in valid_rows:
             win.addnstr(row, 1, '{author} {subreddit}'.format(**data), n_cols-1)
 
-
 def main():
 
     with curses_session() as stdscr:
diff --git a/rtv/viewer.py b/rtv/viewer.py
new file mode 100644
index 0000000..4b22dd8
--- /dev/null
+++ b/rtv/viewer.py
@@ -0,0 +1,115 @@
+import curses
+
+class Navigator(object):
+    """
+    Handles cursor movement and screen paging.
+    """
+
+    def __init__(
+            self,
+            valid_page_cb,
+            page_index=0,
+            cursor_index=0,
+            inverted=False):
+
+        self._page_cb = valid_page_cb
+
+        self.page_index = page_index
+        self.cursor_index = cursor_index
+        self.inverted = inverted
+
+    @property
+    def step(self):
+        return 1 if not self.inverted else -1
+
+    @property
+    def position(self):
+        return (self.page_index, self.cursor_index, self.inverted)
+
+    def move(self, direction, n_windows):
+        "Move the cursor down (positive direction) or up (negative direction)"
+
+        valid, redraw = True, False
+
+        # TODO: add variable movement
+        forward = ((direction*self.step) > 0)
+
+        if forward:
+            self.cursor_index += 1
+            if self.cursor_index >= n_windows - 1:
+                self.page_index += (self.step * self.cursor_index)
+                self.cursor_index = 0
+                self.inverted = not self.inverted
+                redraw = True
+        else:
+            if self.cursor_index > 0:
+                self.cursor_index -= 1
+            else:
+                if self._is_valid(self.page_index - self.step):
+                    self.page_index -= self.step
+                    redraw = True
+                else:
+                    valid = False
+
+        return valid, redraw
+
+    def _is_valid(self, page_index):
+        "Check if a page index will cause entries to fall outside valid range"
+
+        try:
+            self._page_cb(page_index)
+            self._page_cb(page_index + self.step * self.cursor_index)
+        except IndexError:
+            return False
+        else:
+            return True
+
+
+class BaseViewer(object):
+    """
+    Base terminal viewer incorperating a cursor to navigate content
+    """
+
+    def __init__(self, content):
+
+        self.content = content
+        self.nav = Navigator(self.content.get)
+
+    def draw_content(self):
+        raise NotImplementedError
+
+    @property
+    def n_subwindows(self):
+        raise NotImplementedError
+
+    def move_cursor_up(self):
+        self._move_cursor(-1)
+
+    def move_cursor_down(self):
+        self._move_cursor(1)
+
+    def add_cursor(self):
+        self._edit_cursor(curses.A_REVERSE)
+
+    def remove_cursor(self):
+        self._edit_cursor(curses.A_NORMAL)
+
+    def _move_cursor(self, direction):
+
+        self.remove_cursor()
+
+        valid, redraw = self.nav.move(direction, self.n_subwindows)
+        if not valid:
+            curses.flash()
+        if redraw:
+            self.draw_content()
+
+        self.add_cursor()
+
+    def _edit_cursor(self, attribute):
+
+        window = self._sub_windows[self.nav.cursor_index]
+        n_rows, _ = window.getmaxyx()
+        for row in xrange(n_rows):
+            window.chgat(row, 0, 1, attribute)
+        window.refresh()
\ No newline at end of file