// Package rectangles find rectangles in ASCII diagrams.
package rectangles
const corner = '+'
var (
	cHorizontal = []byte{corner, '-'}
	cVertical   = []byte{corner, '|'}
)
// Count returns the number of rectangles found in input ASCII diagram.
func Count(input []string) int {
	ret := 0
	for j, line := range input {
		for i, ch := range line {
			if ch == corner {
				// we are on the top-left corner of a possible rectangle
				for right := i + 1; right < len(line) &&
					continous(line[right], cHorizontal); right++ {
					// we are going right on valid edges, searching for next corner
					if line[right] == corner {
						// we are on top-right corner of a possible rectangle
						for down := j + 1; down < len(input) &&
							continous(input[down][i], cVertical) &&
							continous(input[down][right], cVertical); down++ {
							// we are going down on valid edges (left and right both)
							if input[down][i] == corner &&
								input[down][right] == corner {
								// we have a corner on both left and right position
								// so this is a rectangle
								ret++
							}
						}
					}
				}
			}
		}
	}
	return ret
}
// continous checks in an edge is valid.
func continous(in byte, ok []byte) bool {
	for _, r := range ok {
		if in == r {
			return true
		}
	}
	return false
}