package catalogue

import (
	"strings"
	"testing"
)

// A module whose files cannot be written in advance.
//
// The mesh's private network is the case: a machine's peer list is derived from every other
// machine, so it differs on each one and changes when any of them changes. What matters in these
// tests is not that it works, but that being computed changes *nothing else* about being a
// module — it is assigned, resolved, settled and absent when nobody asked for it.

type fake struct {
	on    map[string]bool
	asked []string
	err   error
}

func (f *fake) Resources(node string) ([]map[string]any, bool, error) {
	f.asked = append(f.asked, node)
	if f.err != nil {
		return nil, false, f.err
	}
	if !f.on[node] {
		return nil, false, nil
	}
	return []map[string]any{{"id": "peers", "type": "file", "path": "/etc/x.conf",
		"merge": MergeJSON, "content": `{"peer":"` + node + `"}`}}, true, nil
}

func computedShelf() map[string]Manifest {
	return shelf(Manifest{Module: "mesh-network", Computed: "mesh-network",
		Provides: Offers("private-network")})
}

func TestAComputedModuleIsAskedAboutTheNodeItIsFor(t *testing.T) {
	// The generator gets a node name, not a plan. Everything it needs is the whole mesh, which
	// it was built with — this is the one thing a node could never work out for itself.
	got, err := Resolve(computedShelf(), []string{"mesh-network"}, workstation(), World{})
	if err != nil {
		t.Fatal(err)
	}
	gen := &fake{on: map[string]bool{"workstation": true}}
	out, err := got.Declaration(Rendering{Generators: map[string]Generator{"mesh-network": gen}})
	if err != nil {
		t.Fatal(err)
	}
	if len(gen.asked) != 1 || gen.asked[0] != "workstation" {
		t.Fatalf("asked about %v, wanted workstation once", gen.asked)
	}
	if len(out) != 1 || !strings.Contains(out[0]["content"].(string), `"peer": "workstation"`) {
		t.Fatalf("got %v", out)
	}
}

func TestAMachineNobodyGaveItGetsNothing(t *testing.T) {
	// The whole point of making the network a module. Before this, every machine with an address
	// was on the private network and there was no way to say one should stay off.
	got, err := Resolve(computedShelf(), nil, workstation(), World{})
	if err != nil {
		t.Fatal(err)
	}
	gen := &fake{on: map[string]bool{"workstation": true}}
	out, err := got.Declaration(Rendering{Generators: map[string]Generator{"mesh-network": gen}})
	if err != nil {
		t.Fatal(err)
	}
	if len(out) != 0 {
		t.Fatalf("a machine that was assigned nothing got %d resource(s)", len(out))
	}
	if len(gen.asked) != 0 {
		t.Fatalf("the generator was asked about %v, and nobody had asked for it", gen.asked)
	}
}

func TestAssignedAndNotYetPartOfItIsNotAFailure(t *testing.T) {
	// A machine given the network module before it has a place on it. Brief and ordinary — the
	// answer is "nothing yet", and treating it as an error would make an ordering a fault.
	got, _ := Resolve(computedShelf(), []string{"mesh-network"}, workstation(), World{})
	gen := &fake{on: map[string]bool{}}
	out, err := got.Declaration(Rendering{Generators: map[string]Generator{"mesh-network": gen}})
	if err != nil {
		t.Fatalf("refused a node that is not on the network yet: %v", err)
	}
	if len(out) != 0 {
		t.Fatalf("got %v", out)
	}
}

func TestAGeneratorThisControlPlaneDoesNotHaveIsRefused(t *testing.T) {
	// Sending a machine a module with no files would look like it worked. Named in the message,
	// because the only fix is a control plane that has it.
	got, _ := Resolve(shelf(Manifest{Module: "weather", Computed: "the-weather"}), []string{"weather"}, workstation(), World{})

	_, err := got.Declaration(Rendering{Generators: map[string]Generator{"mesh-network": &fake{}}})
	if err == nil {
		t.Fatal("a module computed by nothing was accepted")
	}
	if !strings.Contains(err.Error(), "the-weather") {
		t.Fatalf("the refusal does not name what is missing: %v", err)
	}
}

func TestAModuleIsEitherWrittenOrComputedNotBoth(t *testing.T) {
	// Otherwise nobody could say where a given file on a machine came from.
	_, err := ParseManifest([]byte(`{"module":"mesh-network","version":"1",
		"computed":"mesh-network",
		"resources":[{"id":"a","type":"package","package":"wireguard-tools"}]}`))
	if err == nil {
		t.Fatal("a module that both ships files and has them computed was accepted")
	}
	if !strings.Contains(err.Error(), "one or the other") {
		t.Fatalf("unhelpful refusal: %v", err)
	}
}

func TestSettingsApplyToAComputedModuleToo(t *testing.T) {
	// Being computed is about where the files come from, not about whether they are configurable.
	// A line drawn there would be arbitrary and nobody could predict it.
	got, _ := Resolve(computedShelf(), []string{"mesh-network"}, workstation(), World{})
	gen := &fake{on: map[string]bool{"workstation": true}}
	out, err := got.Declaration(Rendering{
		Generators: map[string]Generator{"mesh-network": gen},
		Settings: SettingsBy{"mesh-network": {{From: "the mesh",
			Values: map[string]any{"keepalive": 25}}}},
	})
	if err != nil {
		t.Fatal(err)
	}
	content := out[0]["content"].(string)
	if !strings.Contains(content, `"keepalive": 25`) {
		t.Fatalf("the setting did not reach a computed file: %s", content)
	}
	if !strings.Contains(content, `"peer": "workstation"`) {
		t.Fatalf("the setting replaced what the generator computed: %s", content)
	}
}

func TestTwoWaysToBeOnAPrivateNetworkRefuseAndNameBoth(t *testing.T) {
	// WireGuard is one way. The refusing rule is what makes a second one safe to add: assigning
	// both is caught rather than producing a machine on two networks that each half-work.
	_, err := Resolve(shelf(
		Manifest{Module: "mesh-network", Computed: "mesh-network",
			Provides: Offers("private-network")},
		Manifest{Module: "tailscale", Provides: Offers("private-network")},
		Manifest{Module: "backups", Requires: []string{"private-network"}},
	), []string{"backups"}, workstation(), World{})

	if err == nil {
		t.Fatal("two answers to one requirement were taken silently")
	}
	for _, want := range []string{"mesh-network", "tailscale", "private-network"} {
		if !strings.Contains(err.Error(), want) {
			t.Fatalf("the refusal does not name %s: %v", want, err)
		}
	}
}