// Thanks to https://github.com/mattyork/fuzzy
class TributeSearch {
    constructor(tribute) {
        this.tribute = tribute
        this.tribute.search = this
    }

    simpleFilter(pattern, array) {
        return array.filter(string => {
            return this.test(pattern, string)
        })
    }

    test(pattern, string) {
        return this.match(pattern, string) !== null
    }

    match(pattern, string, opts) {
        opts = opts || {}
        let patternIdx = 0,
            result = [],
            len = string.length,
            totalScore = 0,
            currScore = 0,
            pre = opts.pre || '',
            post = opts.post || '',
            compareString = opts.caseSensitive && string || string.toLowerCase(),
            ch, compareChar

        if (opts.skip) {
            return {rendered: string, score: 0}
        }

        pattern = opts.caseSensitive && pattern || pattern.toLowerCase()

        let patternCache = this.traverse(compareString, pattern, 0, 0, [])
        if (!patternCache) {
            return null
        }
        return {
            rendered: this.render(string, patternCache.cache, pre, post),
            score: patternCache.score
        }
    }

    traverse(string, pattern, stringIndex, patternIndex, patternCache) {
        // if the pattern search at end
        if (pattern.length === patternIndex) {

            // calculate score and copy the cache containing the indices where it's found
            return {
                score: this.calculateScore(patternCache),
                cache: patternCache.slice()
            }
        }

        // if string at end or remaining pattern > remaining string
        if (string.length === stringIndex || pattern.length - patternIndex > string.length - stringIndex) {
            return undefined
        }

        let c = pattern[patternIndex]
        let index = string.indexOf(c, stringIndex)
        let best, temp

        while (index > -1) {
            patternCache.push(index)
            temp = this.traverse(string, pattern, index + 1, patternIndex + 1, patternCache)
            patternCache.pop()

            // if downstream traversal failed, return best answer so far
            if (!temp) {
                return best
            }

            if (!best || best.score < temp.score) {
                best = temp
            }

            index = string.indexOf(c, index + 1)
        }

        return best
    }

    calculateScore(patternCache) {
        let score = 0
        let temp = 1

        patternCache.forEach((index, i) => {
            if (i > 0) {
                if (patternCache[i - 1] + 1 === index) {
                    temp += temp + 1
                }
                else {
                    temp = 1
                }
            }

            score += temp
        })

        return score
    }

    render(string, indices, pre, post) {
        var rendered = string.substring(0, indices[0])

        indices.forEach((index, i) => {
            rendered += pre + string[index] + post +
                string.substring(index + 1, (indices[i + 1]) ? indices[i + 1] : string.length)
        })

        return rendered
    }

    filter(pattern, arr, opts) {
        opts = opts || {}
        return arr
            .reduce((prev, element, idx, arr) => {
                let str = element

                if (opts.extract) {
                    str = opts.extract(element)

                    if (!str) { // take care of undefineds / nulls / etc.
                        str = ''
                    }
                }

                let rendered = this.match(pattern, str, opts)

                if (rendered != null) {
                    prev[prev.length] = {
                        string: rendered.rendered,
                        score: rendered.score,
                        index: idx,
                        original: element
                    }
                }

                return prev
            }, [])

        .sort((a, b) => {
            let compare = b.score - a.score
            if (compare) return compare
            return a.index - b.index
        })
    }
}

export default TributeSearch;