"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 statement 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)