Reorganize state

state/cell.go

@@ -0,0 +1,104 @@
+package state
+
+const (
+	statebit    = 1             // the current state of the cell (for field)
+	flagbit     = statebit << 1 // whether or not the cell has been flagged as empty (for field)
+	markbit     = statebit << 2 // whether or not the cell has been flagged as full (for field)
+	correctbit  = statebit << 3 // whether or not the cell is correct (for field, section)
+	completebit = statebit << 4 // whether or not the cell is complete (for section)
+)
+
+// Cells {{{
+
+// cell represents a single entry in the field managing various states.
+type cell byte
+
+// state returns whether the cell is alive or dead.
+func (c cell) state() bool {
+	return (c & statebit) != 0
+}
+
+// correct returns whether or not the cell has been guessed correctly, or the section is made up of entirely correct guesses.
+func (c cell) correct() bool {
+	return (c & correctbit) != 0
+}
+
+// complete marks the section as complete (that is, all sections in its row/column are correct.
+func (c cell) complete() bool {
+	return (c & completebit) != 0
+}
+
+// flagged returns whether or not the cell is suspected to be dead.
+func (c cell) flagged() bool {
+	return (c & flagbit) != 0
+}
+
+// marked returns whether or not the cell is suspected to be alive.
+func (c cell) marked() bool {
+	return (c & markbit) != 0
+}
+
+// vivify sets the state of the cell to alive.
+func (c cell) vivify() cell {
+	c = c | statebit
+	if c.marked() {
+		return c.setCorrect(true)
+	} else {
+		return c.setCorrect(false)
+	}
+}
+
+// kill sets the state of the cell to dead.
+func (c cell) kill() cell {
+	c = c &^ statebit
+	if c.flagged() {
+		return c.setCorrect(true)
+	} else {
+		return c.setCorrect(false)
+	}
+}
+
+// setCorrect marks the cell as being guessed correctly, or the section being made up of entirely correct guesses.
+func (c cell) setCorrect(to bool) cell {
+	if to {
+		return c | correctbit
+	} else {
+		return c &^ correctbit
+	}
+}
+
+// setComplete marks the section as complete (that is, all sections in its row/column are correct).
+func (c cell) setComplete(to bool) cell {
+	if to {
+		return c | completebit
+	} else {
+		return c &^ completebit
+	}
+}
+
+// mark marks a bit as suspected alive.
+func (c cell) mark() cell {
+	c |= markbit
+	c = c &^ flagbit
+	if c.state() {
+		return c.setCorrect(true)
+	} else {
+		return c.setCorrect(false)
+	}
+}
+
+// flag marks a bit as suspected dead.
+func (c cell) flag() cell {
+	c |= flagbit
+	c = c &^ markbit
+	if c.state() {
+		return c.setCorrect(false)
+	} else {
+		return c.setCorrect(true)
+	}
+}
+
+// clear clears all bits except for the status.
+func (c cell) clear() cell {
+	return c &^ (markbit | flagbit | correctbit | completebit)
+}