package enrich

import (
	"sort"
	"strings"
	"unicode"
)

// KeywordExtractor extracts keywords from text
type KeywordExtractor struct{}

// NewKeywordExtractor creates a new KeywordExtractor
func NewKeywordExtractor() *KeywordExtractor {
	return &KeywordExtractor{}
}

// Extract extracts keywords from text and returns them
func (e *KeywordExtractor) Extract(text Text) ([]Keyword, error) {
	// This is a simplified implementation
	// In a real-world scenario, you would use a library like github.com/jdkato/prose
	// or call an external API for keyword extraction

	content := strings.ToLower(text.Body)

	// Split into words
	words := strings.FieldsFunc(content, func(r rune) bool {
		return !unicode.IsLetter(r) && !unicode.IsNumber(r)
	})

	// Count word frequencies
	wordFreq := make(map[string]int)
	for _, word := range words {
		if len(word) > 2 { // Skip very short words
			wordFreq[word]++
		}
	}

	// Filter out stop words
	for word := range wordFreq {
		if isStopWord(word) {
			delete(wordFreq, word)
		}
	}

	// Convert to keywords
	keywords := make([]Keyword, 0, len(wordFreq))
	totalWords := len(words)
	for word, count := range wordFreq {
		// Calculate relevance based on frequency
		relevance := float64(count) / float64(totalWords)

		// Boost longer words slightly
		relevance *= (1.0 + float64(len(word))/20.0)

		keywords = append(keywords, Keyword{
			Text:      word,
			Relevance: relevance,
		})
	}

	// Sort by relevance
	sort.Slice(keywords, func(i, j int) bool {
		return keywords[i].Relevance > keywords[j].Relevance
	})

	// Limit to top keywords
	maxKeywords := 20
	if len(keywords) > maxKeywords {
		keywords = keywords[:maxKeywords]
	}

	return keywords, nil
}

// isStopWord checks if a word is a common stop word
func isStopWord(word string) bool {
	stopWords := map[string]bool{
		"a": true, "about": true, "above": true, "after": true, "again": true,
		"against": true, "all": true, "am": true, "an": true, "and": true,
		"any": true, "are": true, "as": true, "at": true, "be": true,
		"because": true, "been": true, "before": true, "being": true, "below": true,
		"between": true, "both": true, "but": true, "by": true, "can": true,
		"did": true, "do": true, "does": true, "doing": true, "don": true,
		"down": true, "during": true, "each": true, "few": true, "for": true,
		"from": true, "further": true, "had": true, "has": true, "have": true,
		"having": true, "he": true, "her": true, "here": true, "hers": true,
		"herself": true, "him": true, "himself": true, "his": true, "how": true,
		"i": true, "if": true, "in": true, "into": true, "is": true,
		"it": true, "its": true, "itself": true, "just": true, "me": true,
		"more": true, "most": true, "my": true, "myself": true, "no": true,
		"nor": true, "not": true, "now": true, "of": true, "off": true,
		"on": true, "once": true, "only": true, "or": true, "other": true,
		"our": true, "ours": true, "ourselves": true, "out": true, "over": true,
		"own": true, "same": true, "she": true, "should": true, "so": true,
		"some": true, "such": true, "than": true, "that": true, "the": true,
		"their": true, "theirs": true, "them": true, "themselves": true, "then": true,
		"there": true, "these": true, "they": true, "this": true, "those": true,
		"through": true, "to": true, "too": true, "under": true, "until": true,
		"up": true, "very": true, "was": true, "we": true, "were": true,
		"what": true, "when": true, "where": true, "which": true, "while": true,
		"who": true, "whom": true, "why": true, "will": true, "with": true,
		"would": true, "you": true, "your": true, "yours": true, "yourself": true,
		"yourselves": true,
	}

	return stopWords[word]
}