package engine

import (
	"context"
	"testing"
)

// TestGoldenScoringSnapshot is the behavior preservation harness for the three tool separation. It
// scores a fixed set of candidates against one fixed requirement through the shared engine and asserts
// the EXACT sub scores, total, and band for each. The three tools (screenMATCH, slateMATCH,
// missionMATCH) all call this one engine, so these golden values are the contract: re run this after
// every workstream and prove the numbers are byte identical. A drift here means a refactor changed a
// score, which the acceptance criteria forbid. The candidates span all three bands (Green, Yellow,
// Red) so a band cut change is caught too.
//
// The requirement is perfectRequirement(): Secret, no poly, mandatory AWS and Go, Security+, DISA
// customer, 5 years, Fort Meade with no remote.
func TestGoldenScoringSnapshot(t *testing.T) {
	req := perfectRequirement()

	type want struct {
		clearance, skills, certs, customer, experience, location string
		total                                                    string
		band                                                     Band
		gaps                                                     int
	}

	cases := []struct {
		name string
		cand Candidate
		want want
	}{
		{
			// Every dimension perfect. Total 100.00, Green, no gaps.
			name: "green perfect",
			cand: perfectCandidate(),
			want: want{
				clearance: "100", skills: "100", certs: "100", customer: "100",
				experience: "100", location: "100", total: "100.00", band: BandGreen, gaps: 0,
			},
		},
		{
			// Clearance, customer, certs, experience, location perfect; one of two mandatory skills met.
			// Skills 50. Total 25+12.5+15+15+10+10 = 87.50, Yellow, one mandatory skill gap (Go).
			name: "yellow one skill short",
			cand: Candidate{
				ID:                 "cand-yellow",
				Clearance:          Clearance{Level: ClearanceSecret, Poly: PolyNone, Status: StatusActive},
				Skills:             []CandidateSkill{{SkillID: "sk-aws", Name: "AWS"}},
				Certifications:     []string{"Security+"},
				CustomerExperience: []string{"DISA"},
				YearsExperience:    5,
				Location:           "Fort Meade, MD",
				Available:          true,
			},
			want: want{
				clearance: "100", skills: "50", certs: "100", customer: "100",
				experience: "100", location: "100", total: "87.50", band: BandYellow, gaps: 1,
			},
		},
		{
			// Confidential cannot satisfy Secret so clearance is 0; one skill of two; no certs; no DISA;
			// 3 of 5 years (60); wrong location but relocatable (50) and available (100) so location 75.
			// Total 0+12.5+0+0+6+7.5 = 26.00, Red. Gaps: clearance, mandatory Go, Security+.
			name: "red underqualified",
			cand: Candidate{
				ID:                 "cand-red",
				Clearance:          Clearance{Level: ClearanceConfidential, Poly: PolyNone, Status: StatusActive},
				Skills:             []CandidateSkill{{SkillID: "sk-aws", Name: "AWS"}},
				Certifications:     nil,
				CustomerExperience: nil,
				YearsExperience:    3,
				Location:           "Denver, CO",
				Relocatable:        true,
				Available:          true,
			},
			want: want{
				clearance: "0", skills: "50", certs: "0", customer: "0",
				experience: "60", location: "75", total: "26.00", band: BandRed, gaps: 3,
			},
		},
	}

	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			res := ScoreCandidate(context.Background(), tc.cand, req, nil)
			eq(t, res.Clearance, tc.want.clearance)
			eq(t, res.Skills, tc.want.skills)
			eq(t, res.Certifications, tc.want.certs)
			eq(t, res.CustomerExperience, tc.want.customer)
			eq(t, res.Experience, tc.want.experience)
			eq(t, res.Location, tc.want.location)
			if res.Total.StringFixed(2) != tc.want.total {
				t.Fatalf("total %s, want %s", res.Total.StringFixed(2), tc.want.total)
			}
			if res.Band != tc.want.band {
				t.Fatalf("band %s, want %s", res.Band, tc.want.band)
			}
			if len(res.GapSummary) != tc.want.gaps {
				t.Fatalf("gap count %d, want %d: %v", len(res.GapSummary), tc.want.gaps, res.GapSummary)
			}
			// The weighted trace must always re sum to the total: the AEDT explainability invariant.
			sum := zero
			for _, comp := range res.Trace {
				sum = sum.Add(comp.Weighted)
			}
			if !sum.Round(2).Equal(res.Total) {
				t.Fatalf("trace sum %s != total %s", sum.Round(2), res.Total)
			}
		})
	}
}