package boxchoice

import (
	"reflect"
	"testing"
	"time"
)

var policyNow = time.Date(2026, 10, 16, 12, 0, 0, 0, time.UTC)

// roomy is a candidate every §7 rule passes at policyNow.
func roomy(id string, memFree int64) Candidate {
	return Candidate{BoxID: id, Region: "eu-west-2", MemFreeMiB: memFree, MemTotalMiB: 8000, DiskFreeMiB: 50000, DiskTotalMiB: 100000,
		Generation: policyNow.Add(-5 * time.Minute).Format(time.RFC3339)}
}

func TestPlaceableAppliesEachRule(t *testing.T) {
	gen := func(d time.Duration) string { return policyNow.Add(d).Format(time.RFC3339) }
	cases := []struct {
		name string
		mut  func(*Candidate)
		role string
		want bool
	}{
		{"every rule holds", nil, "", true},
		{"memory exactly 15%", func(c *Candidate) { c.MemFreeMiB = 1200 }, "", true},
		{"memory under 15%", func(c *Candidate) { c.MemFreeMiB = 1199 }, "", false},
		{"no memory total", func(c *Candidate) { c.MemTotalMiB = 0 }, "", false},
		{"disk exactly 10%", func(c *Candidate) { c.DiskFreeMiB = 10000 }, "", true},
		{"disk under 10%", func(c *Candidate) { c.DiskFreeMiB = 9999 }, "", false},
		{"no disk total", func(c *Candidate) { c.DiskTotalMiB = 0 }, "", false},
		{"edges file exactly 15 minutes old", func(c *Candidate) { c.Generation = gen(-15 * time.Minute) }, "", true},
		{"edges file older than 15 minutes", func(c *Candidate) { c.Generation = gen(-15*time.Minute - time.Second) }, "", false},
		{"edges file a minute in the future", func(c *Candidate) { c.Generation = gen(time.Minute) }, "", true},
		{"edges file further in the future", func(c *Candidate) { c.Generation = gen(time.Minute + time.Second) }, "", false},
		{"no generation", func(c *Candidate) { c.Generation = "" }, "", false},
		{"unreadable generation", func(c *Candidate) { c.Generation = "yesterday" }, "", false},
		{"legacy role", nil, "legacy", false},
		{"platform role", nil, "platform", false},
		{"a role this build does not know", nil, "draining", false},
	}
	for _, tc := range cases {
		t.Run(tc.name, func(t *testing.T) {
			c := roomy("i-0aaa", 4000)
			if tc.mut != nil {
				tc.mut(&c)
			}
			got := Placeable([]Candidate{c}, map[string]string{"i-0aaa": tc.role}, policyNow)
			if (len(got) == 1) != tc.want {
				t.Fatalf("placeable = %v, want %v", ids(got), tc.want)
			}
		})
	}
}

func TestExcludeRolesKeepsOrderAndDefaults(t *testing.T) {
	cands := []Candidate{roomy("c", 1), roomy("a", 1), roomy("b", 1)}
	got := ExcludeRoles(cands, map[string]string{"a": "legacy", "b": ""})
	if !reflect.DeepEqual(ids(got), []string{"c", "b"}) {
		t.Fatalf("got %v", ids(got))
	}
	if got := ExcludeRoles(cands, nil); len(got) != 3 {
		t.Fatalf("no roles excluded %v", ids(got))
	}
}

func TestChooseRoomiestSpreadsThenMostMemoryThenHash(t *testing.T) {
	running := map[string]Load{"a": {Hosts: 1, Apps: map[string]int{"bab/jam": 1}}}
	// a has the most memory but already runs the app: spread wins.
	got, ok := ChooseRoomiest("h.example", []Candidate{roomy("a", 7000), roomy("b", 2000), roomy("c", 3000)}, running, "bab/jam")
	if !ok || got.BoxID != "c" {
		t.Fatalf("spread then memory: got %q", got.BoxID)
	}
	// Spread never refuses: every box runs the app, so memory decides.
	all := map[string]Load{"a": running["a"], "b": running["a"]}
	got, _ = ChooseRoomiest("h.example", []Candidate{roomy("a", 1000), roomy("b", 2000)}, all, "bab/jam")
	if got.BoxID != "b" {
		t.Fatalf("all run the app: got %q", got.BoxID)
	}
	// Fewer hosts is no longer a rule: memory beats it.
	busy := map[string]Load{"a": {Hosts: 50}, "b": {Hosts: 1}}
	got, _ = ChooseRoomiest("h.example", []Candidate{roomy("a", 5000), roomy("b", 4000)}, busy, "bab/jam")
	if got.BoxID != "a" {
		t.Fatalf("memory over host count: got %q", got.BoxID)
	}
	// Equal memory: the P5-D2 hash, whatever the order.
	one, _ := ChooseRoomiest("h.example", []Candidate{roomy("a", 1000), roomy("b", 1000)}, nil, "bab/jam")
	two, _ := ChooseRoomiest("h.example", []Candidate{roomy("b", 1000), roomy("a", 1000)}, nil, "bab/jam")
	if one.BoxID != two.BoxID {
		t.Fatalf("order changed the answer: %q %q", one.BoxID, two.BoxID)
	}
	want, _ := Choose("h.example", []Candidate{roomy("a", 1000), roomy("b", 1000)}, nil, "bab/jam")
	if one.BoxID != want.BoxID {
		t.Fatalf("hash tie-break differs from spec 1's: %q, want %q", one.BoxID, want.BoxID)
	}
	if _, ok := ChooseRoomiest("h.example", nil, nil, "bab/jam"); ok {
		t.Fatal("chose from nothing")
	}
}

func TestEligibleCarriesTotalsAndGeneration(t *testing.T) {
	body := haBox("i-0aaa", func(m map[string]any) {
		m["headroom"] = map[string]any{"mem_free_mib": 1000, "disk_free_mib": 2000, "mem_total_mib": 8000, "disk_total_mib": 40000, "awake": 1}
		m["generation"] = "2026-10-16T11:55:00Z"
	})
	got := Eligible(views(t, body), rosterFor("i-0aaa"), "uk", "eu-west-2", "ie", testKeyFP, nil)
	want := Candidate{BoxID: "i-0aaa", Region: "eu-west-2", MemFreeMiB: 1000, DiskFreeMiB: 2000, MemTotalMiB: 8000, DiskTotalMiB: 40000, Awake: 1, Generation: "2026-10-16T11:55:00Z"}
	if len(got) != 1 || got[0] != want {
		t.Fatalf("got %+v, want %+v", got, want)
	}
}