package main

import (
	"testing"
	"time"

	"github.com/novox/mesh-controller/internal/inventory"
	"github.com/novox/mesh-controller/internal/link"
)

// A merge produces a tiered plan (novox/hq ADR 0162): what moved and everything reachable from it,
// sorted so a tier depends only on earlier ones — with the three kinds of dependency told apart.
func TestAMergeIsPlannedInTiersAlongTheThreeKindsOfDependency(t *testing.T) {
	edges := []inventory.Edge{
		// build dependencies: images on the runtime, a plugin on one of them
		{From: "shop", To: "mesh-tools", Kind: inventory.EdgeStandsOn},
		{From: "postgres", To: "mesh-tools", Kind: inventory.EdgeStandsOn},
		{From: "shop-plugin", To: "shop", Kind: inventory.EdgeDeclared},
		// a code dependency: the proxy packages the controller's source — same tier
		{From: "route-proxy", To: "mesh-controller", Kind: inventory.EdgePackages},
		{From: "builder", To: "mesh-controller", Kind: inventory.EdgePackages},
		// runtime dependencies: everything source-built is built by the builder
		{From: "shop", To: "builder", Kind: inventory.EdgeBuiltBy},
		{From: "postgres", To: "builder", Kind: inventory.EdgeBuiltBy},
		{From: "shop-plugin", To: "builder", Kind: inventory.EdgeBuiltBy},
		{From: "route-proxy", To: "builder", Kind: inventory.EdgeBuiltBy},
		{From: "mesh-controller", To: "builder", Kind: inventory.EdgeBuiltBy},
		{From: "mesh-tools", To: "builder", Kind: inventory.EdgeBuiltBy},
		{From: "builder", To: "mesh-tools", Kind: inventory.EdgeStandsOn},
		{From: "unrelated", To: "alpine", Kind: inventory.EdgeStandsOn},
	}
	// The runtime image moved: everything on it, and what is built by what is on it.
	set := reachableFrom([]string{"mesh-tools"}, edges)
	// What stands on the runtime, and the builder that stands on it; not the controller, which the
	// builder merely builds, nor the proxy that packages the controller.
	want := []string{"builder", "mesh-tools", "postgres", "shop", "shop-plugin"}
	if len(set) != len(want) {
		t.Fatalf("reachable from the runtime: %v, want %v", set, want)
	}
	tiers := tiersOf(set, edges)
	pos := map[string]int{}
	for i, tier := range tiers {
		for _, m := range tier {
			pos[m] = i
		}
	}
	if pos["mesh-tools"] != 0 || pos["builder"] != 1 {
		t.Fatalf("the runtime then the builder: %v", tiers)
	}
	if !(pos["shop"] > pos["builder"] && pos["postgres"] > pos["builder"]) {
		t.Fatalf("what the builder builds comes after the builder: %v", tiers)
	}
	if pos["shop-plugin"] <= pos["shop"] {
		t.Fatalf("a plugin after what it is declared on: %v", tiers)
	}
	if hasCycle(tiers, edges) {
		t.Fatalf("no cycle here: %v", tiers)
	}

	// The controller alone moved: the proxy with it, nothing else.
	small := reachableFrom([]string{"mesh-controller"}, edges)
	if len(small) != 3 {
		t.Fatalf("a controller merge rebuilds the controller and what packages it: %v", small)
	}
	// The builder packages the controller's source (same tier by that edge) and the controller is
	// built by the builder (next tier by that one): the builder first, then the controller and the
	// proxy together — a code dependency in one tier, a runtime dependency across tiers.
	smallTiers := tiersOf(small, edges)
	if len(smallTiers) != 2 || smallTiers[0][0] != "builder" || len(smallTiers[1]) != 2 {
		t.Fatalf("the builder, then the controller and the proxy together: %v", smallTiers)
	}
	// The builder alone moved: the builder, and nothing it builds.
	if only := reachableFrom([]string{"builder"}, edges); len(only) != 1 {
		t.Fatalf("a build machine change rebuilds the build machine alone: %v", only)
	}

	// Only a runtime dependency gates on deployment, and only when the module rolls out.
	p := planOfMerge(link.SourceMoved{Owner: "novox", Repo: "mesh-tools", Commit: "abc"}, []string{"mesh-tools"}, edges)
	p.Tier = pos["builder"]
	rollsOut := func(m string) bool { return m == "builder" }
	if g := gates(p, edges, rollsOut); len(g) != 1 || g[0] != "builder" {
		t.Fatalf("the builder gates the tier after it: %v", g)
	}
	p.Tier = 0
	if g := gates(p, edges, rollsOut); len(g) != 0 {
		t.Fatalf("the runtime image is a build dependency and gates nothing: %v", g)
	}
	if g := gates(p, edges, func(string) bool { return false }); len(g) != 0 {
		t.Fatalf("a module that only records its upgrade gates nothing: %v", g)
	}
}

// A gate is open once every machine running the module has reported after it was built.
func TestAGateOpensWhenTheMachinesHaveReportedSinceTheBuild(t *testing.T) {
	built := time.Date(2026, 10, 1, 15, 0, 0, 0, time.UTC)
	before, after := built.Add(-time.Minute), built.Add(time.Minute)
	reports := []inventory.Reported{{Node: "anchor", At: &after}, {Node: "home-server", At: &before}}
	ok, waiting := applied("builder", built, []string{"anchor", "home-server"}, reports)
	if ok || len(waiting) != 1 || waiting[0] != "home-server" {
		t.Fatalf("one machine has not reported since the build: ok=%v waiting=%v", ok, waiting)
	}
	if ok, _ := applied("builder", built, []string{"anchor"}, reports); !ok {
		t.Fatal("the machine that reported after the build holds the gate open")
	}
	if ok, _ := applied("builder", built, nil, reports); !ok {
		t.Fatal("a module running nowhere gates nothing")
	}
}

// A cycle is not lost: what remains is one last tier, and the caller says so.
func TestACycleIsOneLastTierAndSaidSo(t *testing.T) {
	edges := []inventory.Edge{{From: "a", To: "b", Kind: inventory.EdgeStandsOn}, {From: "b", To: "a", Kind: inventory.EdgeStandsOn}}
	tiers := tiersOf([]string{"a", "b"}, edges)
	if len(tiers) != 1 || len(tiers[0]) != 2 || !hasCycle(tiers, edges) {
		t.Fatalf("a cycle should be one tier of two, said: %v", tiers)
	}
}