package magstore

import (
	"reflect"
	"testing"
)

func mem(slate, cand string, approved bool, f ...float64) SlateMember {
	return SlateMember{SlateID: slate, CandidateID: cand, Approved: approved, Features: f}
}

func TestRerankCoeffsInFeatureOrder(t *testing.T) {
	m := Model{Coeffs: map[string]float64{
		"clearance_score": 1, "skills_score": 2, "certs_score": 3,
		"customer_score": 4, "experience_score": 5, "location_score": 6,
	}}
	got := RerankCoeffs(m)
	if !reflect.DeepEqual(got, []float64{1, 2, 3, 4, 5, 6}) {
		t.Fatalf("coeffs must come back in RerankFeatureOrder, got %v", got)
	}
}

func TestOrderMembersByUtilityStableTiebreak(t *testing.T) {
	// weight only the first feature; a higher first feature sorts first.
	coeffs := []float64{1, 0, 0, 0, 0, 0}
	members := []SlateMember{
		mem("s", "low", false, 10, 0, 0, 0, 0, 0),
		mem("s", "high", true, 90, 0, 0, 0, 0, 0),
		mem("s", "mid", false, 50, 0, 0, 0, 0, 0),
	}
	ordered := OrderMembers(coeffs, members)
	got := []string{ordered[0].CandidateID, ordered[1].CandidateID, ordered[2].CandidateID}
	if !reflect.DeepEqual(got, []string{"high", "mid", "low"}) {
		t.Fatalf("must order by utility descending, got %v", got)
	}
}

func TestOrderMembersZeroWeightPreservesEngineOrder(t *testing.T) {
	// zero weights => every utility ties => the stable incoming (engine) order is preserved exactly.
	coeffs := []float64{0, 0, 0, 0, 0, 0}
	members := []SlateMember{
		mem("s", "a", true, 1, 0, 0, 0, 0, 0),
		mem("s", "b", false, 9, 0, 0, 0, 0, 0),
		mem("s", "c", true, 5, 0, 0, 0, 0, 0),
	}
	ordered := OrderMembers(coeffs, members)
	got := []string{ordered[0].CandidateID, ordered[1].CandidateID, ordered[2].CandidateID}
	if !reflect.DeepEqual(got, []string{"a", "b", "c"}) {
		t.Fatalf("a zero weight must preserve the engine order, got %v", got)
	}
}

func TestTopKSelectionUsesApprovedCount(t *testing.T) {
	// two approved on this slate => the top 2 by utility are the selection the ranking nudges.
	coeffs := []float64{1, 0, 0, 0, 0, 0}
	groups := []SlateGroup{{SlateID: "s", Members: []SlateMember{
		mem("s", "top", true, 90, 0, 0, 0, 0, 0),
		mem("s", "second", false, 80, 0, 0, 0, 0, 0),
		mem("s", "third", true, 10, 0, 0, 0, 0, 0),
	}}}
	sel := TopKSelection(coeffs, groups)
	// two approved => top 2 by the weight (top=90, second=80) are selected; third (10) is not.
	if !sel["s|top"] || !sel["s|second"] {
		t.Fatalf("the top two by utility must be selected, got %v", sel)
	}
	if sel["s|third"] {
		t.Fatalf("the third ranked must not be in a top two selection, got %v", sel)
	}
	if len(sel) != 2 {
		t.Fatalf("the selection size must equal the approved count (2), got %d", len(sel))
	}
}

func TestTopKSelectionSkipsUnanimousReject(t *testing.T) {
	// no approvals => nothing is selected (no ordering signal to gate).
	coeffs := []float64{1, 0, 0, 0, 0, 0}
	groups := []SlateGroup{{SlateID: "s", Members: []SlateMember{
		mem("s", "a", false, 90, 0, 0, 0, 0, 0),
		mem("s", "b", false, 10, 0, 0, 0, 0, 0),
	}}}
	if sel := TopKSelection(coeffs, groups); len(sel) != 0 {
		t.Fatalf("a slate with no approvals must select nothing, got %v", sel)
	}
}