package lem

import (
	"testing"
)

func TestFindGaps_UniformCoverage(t *testing.T) {
	entries := []ScoredEntry{
		{ID: "a", Grammar: GrammarScore{VocabRichness: 0.1, TenseEntropy: 0.5, QuestionRatio: 0.1, DomainDepth: 3, VerbDiversity: 10, NounDiversity: 15}},
		{ID: "b", Grammar: GrammarScore{VocabRichness: 0.2, TenseEntropy: 1.0, QuestionRatio: 0.3, DomainDepth: 6, VerbDiversity: 20, NounDiversity: 25}},
		{ID: "c", Grammar: GrammarScore{VocabRichness: 0.3, TenseEntropy: 1.5, QuestionRatio: 0.5, DomainDepth: 9, VerbDiversity: 30, NounDiversity: 35}},
	}
	gaps := FindGaps(entries, 3)
	if gaps == nil {
		t.Fatal("expected non-nil gaps")
	}
	if len(gaps) == 0 {
		t.Error("expected some gap reports")
	}
}

func TestFindGaps_ClusteredData(t *testing.T) {
	// All entries clustered in one corner — grid probes far from cluster should show gaps.
	entries := []ScoredEntry{
		{ID: "a", Grammar: GrammarScore{VocabRichness: 0.10, TenseEntropy: 0.50, QuestionRatio: 0.1, DomainDepth: 3, VerbDiversity: 10, NounDiversity: 15}},
		{ID: "b", Grammar: GrammarScore{VocabRichness: 0.11, TenseEntropy: 0.51, QuestionRatio: 0.11, DomainDepth: 3, VerbDiversity: 10, NounDiversity: 15}},
		{ID: "c", Grammar: GrammarScore{VocabRichness: 0.12, TenseEntropy: 0.52, QuestionRatio: 0.12, DomainDepth: 3, VerbDiversity: 10, NounDiversity: 15}},
	}
	gaps := FindGaps(entries, 2)
	if len(gaps) == 0 {
		t.Error("expected gaps in clustered data")
	}
	// Top gap should have positive distance.
	if gaps[0].AvgDistance <= 0 {
		t.Error("expected positive distance for worst gap")
	}
}

func TestFindGaps_SortedByWorst(t *testing.T) {
	entries := []ScoredEntry{
		{ID: "a", Grammar: GrammarScore{VocabRichness: 0.1, TenseEntropy: 0.3, QuestionRatio: 0.1, DomainDepth: 2, VerbDiversity: 5, NounDiversity: 8}},
		{ID: "b", Grammar: GrammarScore{VocabRichness: 0.5, TenseEntropy: 1.0, QuestionRatio: 0.3, DomainDepth: 5, VerbDiversity: 15, NounDiversity: 20}},
		{ID: "c", Grammar: GrammarScore{VocabRichness: 0.9, TenseEntropy: 1.5, QuestionRatio: 0.8, DomainDepth: 12, VerbDiversity: 30, NounDiversity: 40}},
	}
	gaps := FindGaps(entries, 2)
	if len(gaps) < 2 {
		t.Fatalf("expected at least 2 gaps, got %d", len(gaps))
	}
	// Descending order.
	if gaps[0].AvgDistance < gaps[len(gaps)-1].AvgDistance {
		t.Error("expected gaps sorted descending by AvgDistance")
	}
}

func TestFindGaps_TooFewEntries(t *testing.T) {
	entries := []ScoredEntry{
		{ID: "solo", Grammar: GrammarScore{VocabRichness: 0.1}},
	}
	gaps := FindGaps(entries, 1)
	if gaps != nil {
		t.Error("expected nil for single entry")
	}
}

func TestGapReport_HasFields(t *testing.T) {
	entries := []ScoredEntry{
		{ID: "a", Grammar: GrammarScore{VocabRichness: 0.1, TenseEntropy: 0.5, QuestionRatio: 0.2, DomainDepth: 3, VerbDiversity: 10, NounDiversity: 15}},
		{ID: "b", Grammar: GrammarScore{VocabRichness: 0.9, TenseEntropy: 1.5, QuestionRatio: 0.8, DomainDepth: 12, VerbDiversity: 35, NounDiversity: 45}},
	}
	gaps := FindGaps(entries, 1)
	for _, g := range gaps {
		if g.AvgDistance < 0 {
			t.Error("AvgDistance should be non-negative")
		}
		if len(g.Probe) != 6 {
			t.Errorf("Probe should be 6D, got %d", len(g.Probe))
		}
		if len(g.NearestIDs) == 0 {
			t.Error("NearestIDs should not be empty")
		}
	}
}