// Package interp is an interpolation search
// Moved to https://github.com/dgryski/go-interp
package interp

// modified from http://data.linkedin.com/blog/2010/06/beating-binary-search
func Search(array []int, key int) int {

	min, max := array[0], array[len(array)-1]

	low, high := 0, len(array)-1

	for {
		if key < min {
			return low
		}

		if key > max {
			return high + 1
		}

		// make a guess of the location
		var guess int
		if high == low {
			guess = high
		} else {
			size := high - low
			offset := int(float64(size-1) * (float64(key-min) / float64(max-min)))
			guess = low + offset
		}

		// maybe we found it?
		if array[guess] == key {
			// scan backwards for start of value range
			for guess > 0 && array[guess-1] == key {
				guess--
			}
			return guess
		}

		// if we guessed to high, guess lower or vice versa
		if array[guess] > key {
			high = guess - 1
			max = array[high]
		} else {
			low = guess + 1
			min = array[low]
		}
	}
}