package articlequality

import (
	"math"
	"regexp"
	"sort"
	"strconv"
	"strings"
	"unicode"
)

const Algorithm = "lexical-coverage-depth-v2"

type Document struct {
	ID   string `json:"id"`
	Text string `json:"text"`
}
type Request struct {
	JobID         string     `json:"job_id,omitempty"`
	ArticleType   string     `json:"article_type"`
	Title         string     `json:"title"`
	Problem       string     `json:"problem"`
	Answer        string     `json:"answer"`
	Prerequisites []string   `json:"prerequisites,omitempty"`
	Validation    []string   `json:"validation,omitempty"`
	Troubleshoot  []string   `json:"troubleshooting,omitempty"`
	Categories    []string   `json:"categories,omitempty"`
	Keywords      []string   `json:"keywords,omitempty"`
	Sources       []Document `json:"sources,omitempty"`
}
type Result struct {
	Algorithm            string             `json:"algorithm"`
	Passed               bool               `json:"passed"`
	Score                float64            `json:"score"`
	WordCount            int                `json:"word_count"`
	ContentWordCount     int                `json:"content_word_count"`
	SectionCount         int                `json:"section_count"`
	ParagraphCount       int                `json:"paragraph_count"`
	ListItemCount        int                `json:"list_item_count"`
	LexicalDiversity     float64            `json:"lexical_diversity"`
	Redundancy           float64            `json:"redundancy"`
	EvidenceAlignment    float64            `json:"evidence_alignment"`
	SourceUtilization    float64            `json:"source_utilization"`
	TechnicalSpecificity float64            `json:"technical_specificity"`
	TypeDepthScore       float64            `json:"type_depth_score"`
	Metrics              map[string]float64 `json:"metrics,omitempty"`
	HardFailures         []string           `json:"hard_failures,omitempty"`
	Recommendations      []string           `json:"recommendations,omitempty"`
}

var headingRE = regexp.MustCompile(`(?m)^##+\s+`)
var numberedRE = regexp.MustCompile(`(?m)^\s*\d+[.)]\s+`)
var listRE = regexp.MustCompile(`(?m)^\s*(?:[-*+]\s+|\d+[.)]\s+)`)
var stopwords = map[string]bool{
	"aber": true, "alle": true, "als": true, "auch": true, "auf": true, "aus": true, "bei": true, "bis": true, "das": true, "dass": true, "dem": true, "den": true, "der": true, "des": true, "die": true, "durch": true, "ein": true, "eine": true, "einer": true, "eines": true, "für": true, "hat": true, "im": true, "in": true, "ist": true, "mit": true, "nicht": true, "oder": true, "ohne": true, "sich": true, "sind": true, "und": true, "von": true, "vor": true, "werden": true, "wird": true, "zu": true, "zum": true, "zur": true,
	"a": true, "an": true, "and": true, "are": true, "as": true, "at": true, "be": true, "by": true, "for": true, "from": true, "is": true, "it": true, "of": true, "on": true, "or": true, "that": true, "the": true, "to": true, "with": true,
}

func Evaluate(req Request) Result {
	// Answer is expected to be the final visible body. Structural arrays remain
	// separate metadata for operational gates and must not be counted twice.
	visible := strings.TrimSpace(strings.Join([]string{req.Title, req.Problem, req.Answer}, "\n\n"))
	all := tokenize(visible, false)
	content := tokenize(visible, true)
	uniqueContent := tokenSet(content)
	sourceSets := make([]map[string]bool, 0, len(req.Sources))
	df := map[string]int{}
	for _, d := range req.Sources {
		set := tokenSet(tokenize(d.Text, true))
		sourceSets = append(sourceSets, set)
		for t := range set {
			df[t]++
		}
	}
	paras := paragraphs(visible)
	redundancy := paragraphRedundancy(paras)
	alignment, specificity := weightedAlignment(content, df, len(req.Sources))
	utilization := sourceUtilization(uniqueContent, sourceSets)
	lexical := 0.0
	if len(content) > 0 {
		lexical = float64(len(uniqueContent)) / float64(len(content))
	}
	sections := len(headingRE.FindAllStringIndex(req.Problem+"\n"+req.Answer, -1))
	listItems := len(listRE.FindAllStringIndex(req.Problem+"\n"+req.Answer, -1))
	r := Result{Algorithm: Algorithm, WordCount: len(all), ContentWordCount: len(content), SectionCount: sections, ParagraphCount: len(paras), ListItemCount: listItems, LexicalDiversity: lexical, Redundancy: redundancy, EvidenceAlignment: alignment, SourceUtilization: utilization, TechnicalSpecificity: specificity}
	return NormalizeResult(req, r)
}

// NormalizeResult reconstructs all decision-bearing values from bounded counters
// and metrics. Agent workers therefore cannot inject free-form rewrite text or
// choose pass/fail themselves; the Brain applies the same canonical rules again.
func NormalizeResult(req Request, r Result) Result {
	r.Algorithm = Algorithm
	r.TypeDepthScore = typeDepth(normalizeType(req.ArticleType), r.WordCount, r.SectionCount, r.ListItemCount, len(req.Validation), len(req.Troubleshoot))
	// EvidenceAlignment is deliberately a soft signal. Lexical overlap is useful for
	// detecting gross drift, but paraphrased multi-source synthesis (especially in
	// German) must not be rejected before the semantic claim reviewer can inspect it.
	r.Score = clamp01(.30*r.TypeDepthScore + .10*r.EvidenceAlignment + .24*r.SourceUtilization + .14*r.TechnicalSpecificity + .12*clamp01(r.LexicalDiversity/.55) + .10*(1-r.Redundancy))
	r.Metrics = map[string]float64{"depth": r.TypeDepthScore, "evidence_alignment": r.EvidenceAlignment, "source_utilization": r.SourceUtilization, "technical_specificity": r.TechnicalSpecificity, "lexical_diversity": r.LexicalDiversity, "redundancy": r.Redundancy}
	r.HardFailures, r.Recommendations = hardGates(req, r)
	r.Passed = len(r.HardFailures) == 0
	if !r.Passed && len(r.Recommendations) == 0 {
		r.Recommendations = []string{"Fachliche Tiefe, Quellenabdeckung und Informationsdichte erhöhen."}
	}
	return r
}
func hardGates(req Request, r Result) ([]string, []string) {
	typ := normalizeType(req.ArticleType)
	minWords, minSections := 450, 4
	switch typ {
	case "reference":
		minWords, minSections = 600, 4
	case "concept":
		minWords, minSections = 520, 4
	case "decision_guide":
		minWords, minSections = 520, 4
	case "troubleshooting":
		minWords, minSections = 500, 4
	case "how_to":
		minWords, minSections = 450, 4
	}
	var f, rec []string
	if r.WordCount < minWords {
		f = append(f, "article_too_short")
		repairTarget := minWords + 80
		rec = append(rec, "Artikel fachlich ausarbeiten und die vorhandene Substanz nicht kürzen; für die Revision mindestens etwa "+strconv.Itoa(repairTarget)+" Wörter mit zusätzlichen belegten Details anstreben.")
	}
	if r.SectionCount < minSections {
		f = append(f, "insufficient_section_depth")
		rec = append(rec, "Mehrere artikeltypspezifische Abschnitte mit eigenständigem fachlichem Inhalt ausarbeiten.")
	}
	if len(req.Sources) >= 3 && r.SourceUtilization < .34 {
		f = append(f, "low_source_utilization")
		rec = append(rec, "Mehr der bereitgestellten fachlich relevanten Quellen in konkrete, belegbare Inhalte überführen.")
	}
	// Low lexical overlap is not a hard evidence verdict. A well-grounded synthesis
	// can paraphrase source language heavily, while the subsequent Qwen claim review
	// is explicitly responsible for semantic support/contradiction. Keep the metric
	// observable and only emit a diagnostic recommendation for extreme drift.
	if len(req.Sources) > 0 && r.EvidenceAlignment < .12 {
		rec = append(rec, "Lexikalische Evidenznähe ist niedrig; semantisches Claim-Grounding im Reviewer besonders streng prüfen.")
	}
	if r.Redundancy > .52 {
		f = append(f, "high_redundancy")
		rec = append(rec, "Wiederholungen entfernen und stattdessen zusätzliche technische Details oder Abgrenzungen ergänzen.")
	}
	if r.LexicalDiversity < .24 && r.WordCount > 250 {
		f = append(f, "low_information_density")
		rec = append(rec, "Generische Wiederholungen durch technologiespezifische Erklärungen, Zuordnungen und Beispiele ersetzen.")
	}
	if (typ == "how_to" || typ == "troubleshooting") && (len(numberedRE.FindAllStringIndex(req.Answer, -1)) < 3 || len(req.Validation) < 1) {
		f = append(f, "insufficient_operational_structure")
		rec = append(rec, "Mindestens drei belegte Arbeitsschritte und eine überprüfbare Ergebnisvalidierung angeben.")
	}
	if (typ == "reference" || typ == "concept") && r.ListItemCount < 3 && r.ParagraphCount < 6 {
		f = append(f, "insufficient_explanatory_depth")
		rec = append(rec, "Nicht nur Kernaussagen aufzählen, sondern Zusammenhänge, technische Bedeutung und Grenzen erklären.")
	}
	return unique(f), unique(rec)
}
func normalizeType(v string) string {
	v = strings.ToLower(strings.TrimSpace(v))
	switch v {
	case "reference", "concept", "decision_guide", "troubleshooting", "how_to":
		return v
	}
	return "how_to"
}
func tokenize(s string, filter bool) []string {
	var out []string
	var b strings.Builder
	flush := func() {
		if b.Len() == 0 {
			return
		}
		t := strings.ToLower(b.String())
		b.Reset()
		if len([]rune(t)) < 2 {
			return
		}
		if filter && stopwords[t] {
			return
		}
		out = append(out, t)
	}
	for _, r := range s {
		if unicode.IsLetter(r) || unicode.IsDigit(r) || r == '_' || r == '-' || r == '.' || r == ':' {
			b.WriteRune(r)
		} else {
			flush()
		}
	}
	flush()
	return out
}
func tokenSet(ts []string) map[string]bool {
	m := map[string]bool{}
	for _, t := range ts {
		m[t] = true
	}
	return m
}
func paragraphs(s string) []string {
	parts := regexp.MustCompile(`\n\s*\n`).Split(s, -1)
	out := []string{}
	for _, p := range parts {
		p = strings.TrimSpace(p)
		if len(tokenize(p, false)) >= 5 {
			out = append(out, p)
		}
	}
	return out
}
func weightedAlignment(article []string, df map[string]int, docs int) (float64, float64) {
	if len(article) == 0 || docs == 0 {
		return 0, 0
	}
	seen := map[string]bool{}
	matchedWeight, totalWeight, technicalHits, technicalTotal := 0.0, 0.0, 0.0, 0.0
	for _, t := range article {
		if seen[t] {
			continue
		}
		seen[t] = true
		freq := df[t]
		if freq > 0 {
			// Present evidence terms count fully. Rarer terms get a small bonus, but
			// common cross-source terminology remains valuable instead of being
			// suppressed by inverse-document weighting.
			rarity := math.Log(1 + float64(docs+1)/float64(freq+1))
			w := 1.0 + .25*rarity
			matchedWeight += w
			totalWeight += w
		} else {
			// v1 accidentally gave source-absent words the strongest IDF weight.
			// That made normal explanatory/paraphrased prose dominate the
			// denominator. Unsupported lexical additions now carry only a bounded
			// penalty; semantic support is checked later by the claim reviewer.
			w := .28
			if looksTechnical(t) {
				w = .50
			}
			totalWeight += w
		}
		if looksTechnical(t) {
			technicalTotal++
			if freq > 0 {
				technicalHits++
			}
		}
	}
	alignment := 0.0
	if totalWeight > 0 {
		alignment = matchedWeight / totalWeight
	}
	specificity := alignment
	if technicalTotal > 0 {
		specificity = technicalHits / technicalTotal
	}
	return clamp01(alignment), clamp01(specificity)
}

func sourceUtilization(article map[string]bool, sources []map[string]bool) float64 {
	if len(sources) == 0 {
		return 0
	}
	used := 0
	for _, src := range sources {
		inter, den := 0, 0
		for t := range src {
			if len(t) < 4 {
				continue
			}
			den++
			if article[t] {
				inter++
			}
		}
		if den > 0 && (inter >= 4 || float64(inter)/float64(den) >= .09) {
			used++
		}
	}
	return float64(used) / float64(len(sources))
}
func paragraphRedundancy(ps []string) float64 {
	if len(ps) < 2 {
		return 0
	}
	sets := make([]map[string]bool, len(ps))
	for i, p := range ps {
		sets[i] = tokenSet(tokenize(p, true))
	}
	total := 0.0
	for i := range sets {
		best := 0.0
		for j := range sets {
			if i == j {
				continue
			}
			v := jaccard(sets[i], sets[j])
			if v > best {
				best = v
			}
		}
		total += best
	}
	return clamp01(total / float64(len(sets)))
}
func jaccard(a, b map[string]bool) float64 {
	if len(a) == 0 && len(b) == 0 {
		return 0
	}
	inter := 0
	union := map[string]bool{}
	for k := range a {
		union[k] = true
		if b[k] {
			inter++
		}
	}
	for k := range b {
		union[k] = true
	}
	return float64(inter) / float64(len(union))
}
func typeDepth(typ string, words, sections, listItems, validation, troubleshoot int) float64 {
	tw, ts := 650.0, 5.0
	switch typ {
	case "reference":
		tw, ts = 900, 6
	case "concept":
		tw, ts = 800, 5
	case "decision_guide":
		tw, ts = 800, 5
	case "troubleshooting":
		tw, ts = 750, 6
	}
	w := math.Min(1, float64(words)/tw)
	s := math.Min(1, float64(sections)/ts)
	l := math.Min(1, float64(listItems)/8)
	extra := math.Min(1, float64(validation+troubleshoot)/4)
	if typ == "reference" || typ == "concept" {
		return clamp01(.62*w + .30*s + .08*l)
	}
	return clamp01(.45*w + .25*s + .15*l + .15*extra)
}
func looksTechnical(t string) bool {
	if len(t) >= 7 {
		return true
	}
	for _, r := range t {
		if unicode.IsDigit(r) {
			return true
		}
	}
	return strings.ContainsAny(t, "._:-/")
}
func unique(in []string) []string {
	m := map[string]bool{}
	out := []string{}
	for _, v := range in {
		if v != "" && !m[v] {
			m[v] = true
			out = append(out, v)
		}
	}
	sort.Strings(out)
	return out
}
func clamp01(v float64) float64 {
	if v < 0 {
		return 0
	}
	if v > 1 {
		return 1
	}
	return v
}