From 63269ac7e0c7b75cac9a1df24df8a3520f1f6222 Mon Sep 17 00:00:00 2001
From: Andrew Miner <andrewminer@mac.com>
Date: Sat, 13 Jul 2019 19:52:48 -0600
Subject: [PATCH] Add a new Window class with read/write primitives

---
 src/pycursesui/__init__.py            |   6 +-
 src/pycursesui/attribute_mask.py      |  92 +++++++++++++++++
 src/pycursesui/attribute_mask_spec.py |  53 ++++++++++
 src/pycursesui/session.py             | 141 ++++++++++++++------------
 src/pycursesui/window.py              |  60 +++++++++++
 src/pycursesui/window_spec.py         |  54 ++++++++++
 src/test/main.py                      |  10 +-
 7 files changed, 347 insertions(+), 69 deletions(-)
 create mode 100644 src/pycursesui/attribute_mask.py
 create mode 100644 src/pycursesui/attribute_mask_spec.py
 create mode 100644 src/pycursesui/window.py
 create mode 100644 src/pycursesui/window_spec.py

diff --git a/src/pycursesui/__init__.py b/src/pycursesui/__init__.py
index 5359564..68505ec 100644
--- a/src/pycursesui/__init__.py
+++ b/src/pycursesui/__init__.py
@@ -1,11 +1,15 @@
 """A python UI framework for command-line applications using curses."""
 
+from .attribute_mask import AttributeMask
 from .logger import Logger, LogLevel
+from .window import Window
 
-from .session import Session  # uses Logger
+from .session import Session  # uses Logger, Window
 
 __all__ = [
+    "AttributeMask",
     "Logger",
     "LogLevel",
     "Session",
+    "Window",
 ]
diff --git a/src/pycursesui/attribute_mask.py b/src/pycursesui/attribute_mask.py
new file mode 100644
index 0000000..7e75eb8
--- /dev/null
+++ b/src/pycursesui/attribute_mask.py
@@ -0,0 +1,92 @@
+"""Define the AttributeMask class."""
+
+import curses
+
+
+########################################################################################################################
+
+class AttributeMask(object):
+    """AttributeMask defines the attributes associated with a certain part of the screen."""
+
+    def __init__(self, value: int=curses.A_NORMAL):
+        """Create a new Attribute."""
+        self._value = curses.A_NORMAL
+        self.value = value
+
+    # Properties ###################################################################################
+
+    @property
+    def value(self) -> int:
+        """Get the actual numeric value underlying the mask."""
+        return self._value
+
+    @value.setter
+    def value(self, value: int):
+        if not isinstance(value, int):
+            raise TypeError(f"value must be an int, but was a {type(value)}")
+
+        self._value = value
+
+    # Flag Properties ##############################################################################
+
+    @property
+    def blink(self) -> bool:
+        """Get whether the text is blinking."""
+        return self._read(curses.A_BLINK)
+
+    @blink.setter
+    def blink(self, value: bool):
+        self._assign(curses.A_BLINK, value)
+
+    @property
+    def bold(self) -> bool:
+        """Get whether the text is bolded."""
+        return self._read(curses.A_BOLD)
+
+    @bold.setter
+    def bold(self, value: bool):
+        self._assign(curses.A_BOLD, value)
+
+    @property
+    def dim(self) -> bool:
+        """Get whether the text is dimmed."""
+        return self._read(curses.A_DIM)
+
+    @dim.setter
+    def dim(self, value: bool):
+        self._assign(curses.A_DIM, value)
+
+    @property
+    def standout(self) -> bool:
+        """Get whether the text is standout."""
+        return self._read(curses.A_STANDOUT)
+
+    @standout.setter
+    def standout(self, value: bool):
+        self._assign(curses.A_STANDOUT, value)
+
+    @property
+    def underline(self) -> bool:
+        """Get whether the text is underline."""
+        return self._read(curses.A_UNDERLINE)
+
+    @underline.setter
+    def underline(self, value: bool):
+        self._assign(curses.A_UNDERLINE, value)
+
+    # Private ######################################################################################
+
+    def _assign(self, flag: int, value: bool):
+        if value:
+            self._set(flag)
+        else:
+            self._clear(flag)
+
+    def _clear(self, flag: int):
+        self.value = self.value & (~ flag)
+
+    def _read(self, flag: int) -> bool:
+        return self.value & flag != 0
+
+    def _set(self, flag: int):
+        self.value = self.value | flag
diff --git a/src/pycursesui/attribute_mask_spec.py b/src/pycursesui/attribute_mask_spec.py
new file mode 100644
index 0000000..2b56226
--- /dev/null
+++ b/src/pycursesui/attribute_mask_spec.py
@@ -0,0 +1,53 @@
+"""Unit tests for the AttributeMask class."""
+
+import curses
+import sure
+
+from mamba import before, description, it
+
+from pycursesui import AttributeMask
+
+__all__ = []
+assert sure  # prevent linter errors
+
+
+########################################################################################################################
+
+with description("AttributeMask:", "unit") as self:
+
+    with description("starting with a normal mask"):
+
+        with before.each:
+            self.mask = AttributeMask()
+
+        with it("has all its flags turned off"):
+            self.mask.blink.should.be.false
+            self.mask.bold.should.be.false
+            self.mask.underline.should.be.false
+
+        with description("after activating one of the flags"):
+
+            with before.each:
+                self.mask.bold = True
+
+            with it("only has the bold flag turned on"):
+                self.mask.blink.should.be.false
+                self.mask.bold.should.be.true
+                self.mask.underline.should.be.false
+
+            with it("has the expected value"):
+                self.mask.value.should.equal(curses.A_NORMAL | curses.A_BOLD)
+
+            with description("after switching the flag for another"):
+
+                with before.each:
+                    self.mask.bold = False
+                    self.mask.underline = True
+
+                with it("reports the flags having switched"):
+                    self.mask.blink.should.be.false
+                    self.mask.bold.should.be.false
+                    self.mask.underline.should.be.true
+
+                with it("reports the correct value"):
+                    self.mask.value.should.equal(curses.A_NORMAL | curses.A_UNDERLINE)
diff --git a/src/pycursesui/session.py b/src/pycursesui/session.py
index 8f7a052..c90031f 100644
--- a/src/pycursesui/session.py
+++ b/src/pycursesui/session.py
@@ -2,7 +2,8 @@
 
 import curses
 
-from pycursesui import Logger
+from pycursesui import Logger, Window
+from typing import Callable, Tuple
 
 __all__ = ["Session"]
 
@@ -14,7 +15,7 @@ class Session(object):
 
     def __init__(self, logger=None):
         """Create a new Session."""
-        self._screen = None
+        self._window = None
         self.logger = logger
 
     # Properties ###################################################################################
@@ -22,7 +23,7 @@ class Session(object):
     @property
     def is_running(self) -> bool:
         """Get whether the session is currently active."""
-        return (self.screen is not None)
+        return (self.window is not None)
 
     @property
     def logger(self) -> Logger:
@@ -31,79 +32,91 @@ class Session(object):
 
     @logger.setter
     def logger(self, value: Logger):
-        if value is None:
-            value = Logger()
+        value = value if value is not None else Logger()
         self._logger = value
 
     @property
-    def screen(self):
-        """Get the screen associated with this session (if any)."""
-        return self._screen
+    def window(self) -> Window:
+        """Get the window associated with this session (if any)."""
+        return self._window
 
-    # Magic Methods ################################################################################
+    # Public Methods ###############################################################################
 
-    def __enter__(self):
-        """Enter a session."""
+    def start(self) -> "Session":
+        """
+        Start a new session.
+
+        This will take over the current TTY and begin a curses session. The main window will be available from this
+        object's `window` property. The `stop` method *must* be called to restore the TTY back to its original
+        condition.
+        """
         self.logger.info("Starting curses session")
-        try:
-            self._screen = curses.initscr()
-        except Exception as e:
-            self.logger.error("Could not initialize a curses screen", e)
-            curses.endwin()
-            raise e
 
-        try:
-            curses.noecho()
-        except Exception as e:
-            self.logger.error("Could not set up no ech mode", e)
-            curses.echo()
-            curses.endwin()
-            raise e
+        raw_window, error = self._attempt(lambda: curses.initscr())
+        if raw_window:
+            self._window = Window(raw_window)
+        if error:
+            self.logger.error("could not initialize a curses window", error)
+            self._attempt(lambda: curses.endwin())
+            return None
 
-        try:
-            curses.cbreak()
-        except Exception as e:
-            self.logger.error("Could not set up character break mode", e)
-            curses.nocbreak()
-            curses.echo()
-            curses.endwin()
-            raise e
+        _, error = self._attempt(lambda: curses.start_color())
+        if error:
+            self.logger.error("could not start color session", error)
+            self._attempt(lambda: curses.endwin())
 
-        try:
-            self.screen.keypad(True)
-        except Exception as e:
-            self.logger.error("Could not set up keypad", e)
-            self.screen.keypad(False)
-            curses.nocbreak()
-            curses.echo()
-            curses.endwin()
-            raise e
+        _, error = self._attempt(lambda: curses.noecho())
+        if error:
+            self.logger.error("Could not set up no echo mode", error)
+            self._attempt(lambda: curses.echo())
+            self._attempt(lambda: curses.endwin())
+
+        _, error = self._attempt(lambda: curses.cbreak())
+        if error:
+            self.logger.error("Could not set up chracter break mode", error)
+            self._attempt(lambda: curses.cnobreak())
+            self._attempt(lambda: curses.echo())
+            self._attempt(lambda: curses.endwin())
+
+        _, error = self._attempt(lambda: raw_window.keypad(True))
+        if error:
+            self.logger.error("Could not set up keypad", error)
+            self._attempt(lambda: raw_window.keypad(False))
+            self._attempt(lambda: curses.cnobreak())
+            self._attempt(lambda: curses.echo())
+            self._attempt(lambda: curses.endwin())
 
         return self
 
+    def stop(self) -> "Session":
+        """Stop the current session."""
+        self.logger.info("Shutting down curses session")
+        self._attempt(lambda: self.window.raw.keypad(False))
+        self._attempt(lambda: curses.nocbreak())
+        self._attempt(lambda: curses.echo())
+        self._attempt(lambda: curses.endwin())
+
+        self._window = None
+        return self
+
+    # Magic Methods ################################################################################
+
+    def __enter__(self) -> "Session":
+        """Enter a session."""
+        return self.start()
+
     def __exit__(self, type, value, traceback):
         """Exit a session."""
-        self.logger.info("Shutting down curses session")
-        try:
-            self.screen.keypad(False)
-        except Exception as e:
-            self.logger.error("Could not reset keypad", e)
-
-        try:
-            curses.nocbreak()
-        except Exception as e:
-            self.logger.error("Could not reset character break mode", e)
-
-        try:
-            curses.echo()
-        except Exception as e:
-            self.logger.error("Could not reset echo mode", e)
-
-        try:
-            curses.endwin()
-        except Exception as e:
-            self.logger.error("Could not shut down curses session", e)
-
-        self._screen = None
-
+        self.stop()
         return False
+
+    # Private Methods ##############################################################################
+
+    def _attempt(self, task: Callable) -> Tuple[object, Exception]:
+        result, error = None, None
+        try:
+            result = task()
+        except Exception as e:
+            error = e
+
+        return result, error
diff --git a/src/pycursesui/window.py b/src/pycursesui/window.py
new file mode 100644
index 0000000..014d794
--- /dev/null
+++ b/src/pycursesui/window.py
@@ -0,0 +1,60 @@
+"""Define the Window class."""
+
+from pycursesui import AttributeMask
+
+########################################################################################################################
+
+ENCODING = "ascii"
+
+
+########################################################################################################################
+
+class Window(object):
+    """Window provides a wrapper around a raw curses window."""
+
+    def __init__(self, raw):
+        """Create a new Window wrapper."""
+        self._raw = None
+        self.raw = raw
+
+    # Properties ###################################################################################
+
+    @property
+    def raw(self):
+        """Get the raw curses window wrapped by this object."""
+        return self._raw
+
+    @raw.setter
+    def raw(self, value):
+        if self._raw is not None:
+            raise ValueError("cannot change raw once initialized")
+        if value is None:
+            raise ValueError("a value must be provided for raw")
+
+        self._raw = value
+
+    # Public Methods ###############################################################################
+
+    def read(self, x: int, y: int, length: int=1) -> str:
+        """Read a string from the screen at the given location."""
+        return self.raw.instr(y, x, length).decode(ENCODING)
+
+    def write(self, value: str, x: int, y: int, length: int=-1, attributes: AttributeMask=None):
+        """
+        Write a portion of a string onto the window at a certain location.
+
+        Arguments:
+            value: the string to be written
+            x: the x-coordinate of where the first character should be placed
+            y: the y-coordinate of where the first character should be placed
+            length: the maximum number of characters to write
+            attributes: an Attributes object giving the attributes to be applied
+        """
+        attributes = attributes if attributes is not None else AttributeMask()
+        if (length >= 0) and (len(value) > length):
+            value = value[0:length]
+
+        self.raw.addstr(y, x, value, attributes.value)
+        self.raw.refresh()
+
+        return self
diff --git a/src/pycursesui/window_spec.py b/src/pycursesui/window_spec.py
new file mode 100644
index 0000000..663c2ab
--- /dev/null
+++ b/src/pycursesui/window_spec.py
@@ -0,0 +1,54 @@
+"""Unit tests for the Window class."""
+
+import sure
+
+from io import StringIO
+from mamba import after, before, description, it
+
+from pycursesui import Logger, Session
+from pycursesui.logger import LogLevel
+
+__all__ = []
+assert sure  # prevent linter errors
+
+
+########################################################################################################################
+
+with description("Window:", "unit") as self:
+
+    with before.each:
+        self.session = None
+        try:
+            self.stdout = StringIO()
+            self.logger = Logger().add_channel("debug", self.stdout, LogLevel.DEBUG)
+            self.session = Session(self.logger).start()
+            if self.session is not None:
+                self.window = self.session.window
+        except Exception as e:
+            print(f"log:\n>>>\n{self.stdout.getvalue()}\n<<<\n")
+            raise e
+
+    with after.each:
+        if self.session is not None:
+            self.session.stop()
+
+    with description("using the default window from a new session"):
+
+        with it("doesn't contain any text in the test region"):
+            self.window.read(0, 0, 10).should.equal("          ")
+
+        with description("after writing a string into the test region"):
+
+            with before.each:
+                self.window.write("alpha", 0, 0)
+
+            with it("now contains the written text"):
+                self.window.read(0, 0, 10).should.equal("alpha     ")
+
+        with description("after multiple overlapping writes"):
+
+            with before.each:
+                self.window.write("alpha", 0, 0).write("bravo", 3, 0)
+
+            with it("should have replaced the last portion of the first word"):
+                self.window.read(0, 0, 10).should.equal("alpbravo  ")
diff --git a/src/test/main.py b/src/test/main.py
index 4a4a666..0dce867 100644
--- a/src/test/main.py
+++ b/src/test/main.py
@@ -6,10 +6,12 @@ from pycursesui import Logger, Session
 
 ########################################################################################################################
 
-logger = Logger()
-logger.add_file_channel("main", "session.log")
+logger = Logger().add_file_channel("main", "session.log")
 
 with Session(logger) as session:
-    session.screen.border()
-    session.screen.refresh()
+    session.window.write("alpha", 10, 10)
+    time.sleep(1)
+    session.window.write("bravo", 10, 11)
+    time.sleep(1)
+    session.window.write("charlie", 10, 12)
     time.sleep(3)