package catalogue

import (
	"strings"
	"testing"
)

// A domain module is a module with requirements and no files of its own.
//
// Most people want the network working and do not want to choose a VPN. Some want a particular
// one. Both are the same mechanism: assigning `networking` takes the only answer to each of its
// requirements silently, and the day there are two answers the resolver refuses and names them,
// so choosing is assigning the one you want. There is no flavor field and nothing to configure.

func networkingShelf(extra ...Manifest) map[string]Manifest {
	base := []Manifest{
		{Module: "networking", Requires: []string{"private-network", "name-resolution"}},
		{Module: "mesh-wireguard", Computed: "mesh-wireguard",
			Provides: Offers("private-network", "mesh-addressing"),
			Claims:   []Claim{{Name: "the-private-network", Scope: ScopeNode}}},
		{Module: "mesh-names", Computed: "mesh-names",
			Provides: Offers("name-resolution"), Requires: []string{"mesh-addressing"}},
	}
	return shelf(append(base, extra...)...)
}

func TestOneWordBringsUpTheNetwork(t *testing.T) {
	// The case that has to stay easy. Nothing is asked, because with one answer to each
	// requirement there was never a question.
	got, err := Resolve(networkingShelf(), []string{"networking"}, workstation(), World{})
	if err != nil {
		t.Fatal(err)
	}
	have := strings.Join(names(got), " ")
	for _, want := range []string{"networking", "mesh-wireguard", "mesh-names"} {
		if !strings.Contains(have, want) {
			t.Fatalf("assigning networking did not bring in %s: %s", want, have)
		}
	}
}

func TestASecondVPNTurnsItIntoAChoice(t *testing.T) {
	// And the choice is offered rather than made. A default here would be the flavor field coming
	// back under another name.
	_, err := Resolve(networkingShelf(
		Manifest{Module: "tailscale", Provides: Offers("private-network"),
			Claims: []Claim{{Name: "the-private-network", Scope: ScopeNode}}},
	), []string{"networking"}, workstation(), World{})

	if err == nil {
		t.Fatal("two VPNs and one was picked silently")
	}
	for _, want := range []string{"mesh-wireguard", "tailscale"} {
		if !strings.Contains(err.Error(), want) {
			t.Fatalf("the refusal does not name %s: %v", want, err)
		}
	}
}

func TestChoosingIsAssigning(t *testing.T) {
	// No second verb. Assigning the one you want answers the requirement, and the bundle takes it.
	got, err := Resolve(networkingShelf(
		Manifest{Module: "tailscale",
			Provides: Offers("private-network", "name-resolution"),
			Claims:   []Claim{{Name: "the-private-network", Scope: ScopeNode}}},
	), []string{"networking", "tailscale"}, workstation(), World{})

	if err != nil {
		t.Fatal(err)
	}
	have := strings.Join(names(got), " ")
	if !strings.Contains(have, "tailscale") {
		t.Fatalf("the chosen VPN is not in the set: %s", have)
	}
	if strings.Contains(have, "mesh-wireguard") {
		t.Fatalf("choosing tailscale still installed WireGuard: %s", have)
	}
}

func TestChoosingOneVPNCannotDragTheOtherBackIn(t *testing.T) {
	// This happened. The person chose tailscale; the names module required the mesh's own
	// addressing; only WireGuard provides that; so both were installed and nobody was told.
	//
	// The claim is what catches it. Providing a private network is not the singular part — a
	// machine could run two VPNs for two purposes — but being *the* one the mesh runs over is.
	_, err := Resolve(networkingShelf(
		Manifest{Module: "tailscale", Provides: Offers("private-network"),
			Claims: []Claim{{Name: "the-private-network", Scope: ScopeNode}}},
	), []string{"networking", "tailscale"}, workstation(), World{})

	if err == nil {
		t.Fatal("a machine was given two private networks without being told")
	}
	if !strings.Contains(err.Error(), "the-private-network") {
		t.Fatalf("the refusal does not say what collided: %v", err)
	}
}

func TestNamesNeedTheMeshsOwnAddresses(t *testing.T) {
	// Names are computed from addresses the mesh handed out. Over a VPN that hands out its own,
	// the mesh has nothing to write, so the names module requires the addressing rather than a
	// private network in general — otherwise a machine gets a hosts file full of addresses that
	// mean nothing on it.
	_, err := Resolve(shelf(
		Manifest{Module: "mesh-names", Computed: "mesh-names",
			Provides: Offers("name-resolution"), Requires: []string{"mesh-addressing"}},
		Manifest{Module: "tailscale", Provides: Offers("private-network")},
	), []string{"mesh-names", "tailscale"}, workstation(), World{})

	if err == nil {
		t.Fatal("the mesh's names were installed over a VPN whose addresses it does not hand out")
	}
	if !strings.Contains(err.Error(), "mesh-addressing") {
		t.Fatalf("the refusal does not say what is missing: %v", err)
	}
}

func TestARequirementWantedTwiceIsReportedOnce(t *testing.T) {
	// Two identical lines make a person hunt for the difference between them before realising
	// there is none.
	_, err := Resolve(shelf(
		Manifest{Module: "one", Requires: []string{"shell"}},
		Manifest{Module: "two", Requires: []string{"shell"}},
		Manifest{Module: "bash", Provides: Offers("shell")},
		Manifest{Module: "zsh", Provides: Offers("shell")},
	), []string{"one", "two"}, workstation(), World{})

	if err == nil {
		t.Fatal("two shells and one was picked silently")
	}
	if n := strings.Count(err.Error(), `"shell" is wanted by`); n != 1 {
		t.Fatalf("the same requirement was reported %d times:\n%v", n, err)
	}
}