package link

import (
	"encoding/json"
	"testing"
)

// The contract of order.go, case by case: what a node-engine refuses of a declaration (the rule
// mesh-host states, restated so the controller's tests say what the machines do with what it sends),
// what the controller refuses of a report, and the bytes on the wire both ways.

func TestADeclarationIsOlderOnlyWhenBothClaimAnEpoch(t *testing.T) {
	for _, c := range []struct {
		name     string
		arriving Order
		held     Order
		older    bool
	}{
		{"a newer sequence of the same epoch", Order{57, 12}, Order{57, 11}, false},
		{"the same declaration again (a reconcile)", Order{57, 12}, Order{57, 12}, false},
		{"a lower sequence of the same epoch", Order{57, 11}, Order{57, 12}, true},
		// Issue 204: a controller that lost its lease goes on sending.
		{"an older epoch, whatever its sequence", Order{41, 99}, Order{57, 12}, true},
		{"a newer epoch, whatever its sequence", Order{57, 3}, Order{41, 99}, false},
		{"no epoch arriving: a rolled-back controller is not stranded", Order{0, 11}, Order{57, 12}, false},
		{"no epoch held: what the machine held before any lease", Order{57, 11}, Order{0, 12}, false},
		{"no order at all", Order{}, Order{57, 12}, false},
	} {
		t.Run(c.name, func(t *testing.T) {
			if got := c.arriving.Older(c.held); got != c.older {
				t.Fatalf("%s against %s: older %v, want %v", c.arriving.Words(), c.held.Words(), got, c.older)
			}
		})
	}
}

func TestAnAccountIsOlderByEpochThenSequenceThenReportSequence(t *testing.T) {
	for _, c := range []struct {
		name     string
		arriving Account
		kept     Account
		older    bool
	}{
		// Issue 267: a reconcile's account of declaration 11 arrives after the apply's of 12.
		{"an account of an older declaration", Account{Order{57, 11}, 40}, Account{Order{57, 12}, 41}, true},
		{"an older report of the same declaration", Account{Order{57, 12}, 40}, Account{Order{57, 12}, 41}, true},
		{"a newer report of the same declaration (a reconcile after the apply)",
			Account{Order{57, 12}, 42}, Account{Order{57, 12}, 41}, false},
		{"the same report again (redelivered)", Account{Order{57, 12}, 41}, Account{Order{57, 12}, 41}, false},
		{"an account of a newer declaration, whatever its report sequence",
			Account{Order{57, 13}, 1}, Account{Order{57, 12}, 41}, false},
		{"an account of an older epoch", Account{Order{41, 99}, 50}, Account{Order{57, 12}, 41}, true},
		{"an account of a newer epoch", Account{Order{58, 1}, 2}, Account{Order{57, 12}, 41}, false},
		{"no epoch either side: the sequences", Account{Order{0, 11}, 50}, Account{Order{0, 12}, 41}, true},
		{"no report sequence: the declaration's alone", Account{Order{57, 12}, 0}, Account{Order{57, 12}, 41}, false},
		{"an unordered declaration: the report sequences", Account{Order{}, 40}, Account{Order{}, 41}, true},
		{"nothing kept yet", Account{Order{57, 3}, 1}, Account{}, false},
	} {
		t.Run(c.name, func(t *testing.T) {
			if got := c.arriving.OlderThan(c.kept); got != c.older {
				t.Fatalf("%+v against %+v: older %v, want %v", c.arriving, c.kept, got, c.older)
			}
		})
	}
}

// The bytes, as mesh-host's report writes them: every key optional, absent when zero.
func TestTheOrderOnTheWire(t *testing.T) {
	// A stale refusal, as the node-engine says it: the refused declaration's order at the top, the one
	// it holds in older_than, and how many it has refused ever.
	raw := []byte(`{"node":"anchor","refused":"older","declared":"d1","epoch":41,"sequence":11,` +
		`"report_sequence":7,"older_than":{"epoch":57,"sequence":12},"refused_older":3}`)
	var r Report
	if err := json.Unmarshal(raw, &r); err != nil {
		t.Fatal(err)
	}
	if r.Order != (Order{41, 11}) || r.ReportSequence != 7 || r.OlderThan == nil || *r.OlderThan != (Order{57, 12}) ||
		r.RefusedOlder != 3 {
		t.Fatalf("a node-engine's stale refusal reads as %+v", r)
	}
	if !r.Ordered() || !r.ReadsEpoch() || !r.StaleRefusalOf() {
		t.Fatalf("a node-engine that orders its reports reads as one that does not: %+v", r)
	}

	// A report from a node-engine older than the contract says none of it.
	var older Report
	if err := json.Unmarshal([]byte(`{"node":"anchor","applied":["a"],"declared":"d1"}`), &older); err != nil {
		t.Fatal(err)
	}
	if older.Ordered() || older.ReadsEpoch() || older.StaleRefusalOf() {
		t.Fatalf("an older node-engine's report reads as ordered: %+v", older)
	}
	// Its stale refusal, in the words it has always used, is still one.
	older.Refused = "this declaration " + StaleRefusal + ": it is sequence 3"
	if !older.StaleRefusalOf() {
		t.Fatal("an older node-engine's refusal of an older sequence does not read as stale")
	}

	// And a report with no order puts no order key on the wire.
	raw, err := json.Marshal(Report{Node: "anchor", Declared: "d1"})
	if err != nil {
		t.Fatal(err)
	}
	var keys map[string]any
	if err := json.Unmarshal(raw, &keys); err != nil {
		t.Fatal(err)
	}
	for _, key := range []string{"epoch", "sequence", "report_sequence", "older_than", "refused_older"} {
		if _, there := keys[key]; there {
			t.Fatalf("an unordered report carries %s: %s", key, raw)
		}
	}
}