1 files changed, 106 insertions, 0 deletions
diff --git a/Lib/idlelib/history.py b/Lib/idlelib/history.py
new file mode 100644
index 0000000000..56f53a0f2f
--- /dev/null
+++ b/Lib/idlelib/history.py
@@ -0,0 +1,106 @@
+"Implement Idle Shell history mechanism with History class"
+
+from idlelib.config import idleConf
+
+
+class History:
+    ''' Implement Idle Shell history mechanism.
+
+    store - Store source statement (called from pyshell.resetoutput).
+    fetch - Fetch stored statement matching prefix already entered.
+    history_next - Bound to <<history-next>> event (default Alt-N).
+    history_prev - Bound to <<history-prev>> event (default Alt-P).
+    '''
+    def __init__(self, text):
+        '''Initialize data attributes and bind event methods.
+
+        .text - Idle wrapper of tk Text widget, with .bell().
+        .history - source statements, possibly with multiple lines.
+        .prefix - source already entered at prompt; filters history list.
+        .pointer - index into history.
+        .cyclic - wrap around history list (or not).
+        '''
+        self.text = text
+        self.history = []
+        self.prefix = None
+        self.pointer = None
+        self.cyclic = idleConf.GetOption("main", "History", "cyclic", 1, "bool")
+        text.bind("<<history-previous>>", self.history_prev)
+        text.bind("<<history-next>>", self.history_next)
+
+    def history_next(self, event):
+        "Fetch later statement; start with ealiest if cyclic."
+        self.fetch(reverse=False)
+        return "break"
+
+    def history_prev(self, event):
+        "Fetch earlier statement; start with most recent."
+        self.fetch(reverse=True)
+        return "break"
+
+    def fetch(self, reverse):
+        '''Fetch statememt and replace current line in text widget.
+
+        Set prefix and pointer as needed for successive fetches.
+        Reset them to None, None when returning to the start line.
+        Sound bell when return to start line or cannot leave a line
+        because cyclic is False.
+        '''
+        nhist = len(self.history)
+        pointer = self.pointer
+        prefix = self.prefix
+        if pointer is not None and prefix is not None:
+            if self.text.compare("insert", "!=", "end-1c") or \
+                    self.text.get("iomark", "end-1c") != self.history[pointer]:
+                pointer = prefix = None
+                self.text.mark_set("insert", "end-1c")  # != after cursor move
+        if pointer is None or prefix is None:
+            prefix = self.text.get("iomark", "end-1c")
+            if reverse:
+                pointer = nhist  # will be decremented
+            else:
+                if self.cyclic:
+                    pointer = -1  # will be incremented
+                else:  # abort history_next
+                    self.text.bell()
+                    return
+        nprefix = len(prefix)
+        while 1:
+            pointer += -1 if reverse else 1
+            if pointer < 0 or pointer >= nhist:
+                self.text.bell()
+                if not self.cyclic and pointer < 0:  # abort history_prev
+                    return
+                else:
+                    if self.text.get("iomark", "end-1c") != prefix:
+                        self.text.delete("iomark", "end-1c")
+                        self.text.insert("iomark", prefix)
+                    pointer = prefix = None
+                break
+            item = self.history[pointer]
+            if item[:nprefix] == prefix and len(item) > nprefix:
+                self.text.delete("iomark", "end-1c")
+                self.text.insert("iomark", item)
+                break
+        self.text.see("insert")
+        self.text.tag_remove("sel", "1.0", "end")
+        self.pointer = pointer
+        self.prefix = prefix
+
+    def store(self, source):
+        "Store Shell input statement into history list."
+        source = source.strip()
+        if len(source) > 2:
+            # avoid duplicates
+            try:
+                self.history.remove(source)
+            except ValueError:
+                pass
+            self.history.append(source)
+        self.pointer = None
+        self.prefix = None
+
+
+if __name__ == "__main__":
+    from unittest import main
+    main('idlelib.idle_test.test_history', verbosity=2, exit=False)