package staffing

import (
	"testing"

	"github.com/shopspring/decimal"
)

func dec(s string) decimal.Decimal { return decimal.RequireFromString(s) }

func TestPriorityMultiplier(t *testing.T) {
	ref := decimal.NewFromInt(5_000_000)
	minM := decimal.NewFromInt(1)
	maxM := decimal.NewFromInt(3)
	cases := []struct {
		name  string
		value decimal.Decimal
		want  string
	}{
		{"zero value is minimum", decimal.Zero, "1"},
		{"negative value clamps to minimum", decimal.NewFromInt(-100), "1"},
		{"reference value is midpoint", decimal.NewFromInt(5_000_000), "2"},
		{"double reference hits the cap", decimal.NewFromInt(10_000_000), "3"},
		{"far above reference stays capped", decimal.NewFromInt(50_000_000), "3"},
		{"half reference is 1.5", decimal.NewFromInt(2_500_000), "1.5"},
	}
	for _, c := range cases {
		t.Run(c.name, func(t *testing.T) {
			got := PriorityMultiplier(c.value, ref, minM, maxM)
			if !got.Equal(dec(c.want)) {
				t.Fatalf("PriorityMultiplier(%s) = %s, want %s", c.value, got, c.want)
			}
		})
	}
}

func TestPriorityMultiplierNonPositiveReferenceDisablesWeighting(t *testing.T) {
	got := PriorityMultiplier(decimal.NewFromInt(9_000_000), decimal.Zero, decimal.NewFromInt(1), decimal.NewFromInt(3))
	if !got.Equal(decimal.NewFromInt(1)) {
		t.Fatalf("a non positive reference must return the minimum multiplier, got %s", got)
	}
}

func TestScaledValueKnown(t *testing.T) {
	// total 90, multiplier 2, scale 1e6 -> 180,000,000
	got := ScaledValue(decimal.NewFromInt(90), decimal.NewFromInt(2), 1_000_000)
	if got != 180_000_000 {
		t.Fatalf("ScaledValue = %d, want 180000000", got)
	}
}

func TestScaledValueDeterministicRounding(t *testing.T) {
	// 0.0000005 * 1 * 1e6 = 0.5, shopspring rounds half away from zero -> 1.
	got := ScaledValue(dec("0.0000005"), decimal.NewFromInt(1), 1_000_000)
	if got != 1 {
		t.Fatalf("half away from zero rounding expected 1, got %d", got)
	}
	// Stability: the same input always yields the same integer.
	a := ScaledValue(dec("87.6543"), dec("1.7"), 1_000_000)
	b := ScaledValue(dec("87.6543"), dec("1.7"), 1_000_000)
	if a != b {
		t.Fatalf("ScaledValue is not deterministic: %d vs %d", a, b)
	}
}

func TestScaledValueZeroFitIsZero(t *testing.T) {
	if got := ScaledValue(decimal.Zero, decimal.NewFromInt(3), 1_000_000); got != 0 {
		t.Fatalf("zero fit must be zero value, got %d", got)
	}
}