package catalogue

import (
	"encoding/json"
	"strings"
	"testing"
)

func file(content string, protected ...string) map[string]any {
	r := map[string]any{"id": "conf", "type": "file", "path": "/etc/thing.json",
		"merge": MergeJSON, "content": content}
	if len(protected) > 0 {
		var as []any
		for _, p := range protected {
			as = append(as, p)
		}
		r["protected"] = as
	}
	return r
}

func merged(t *testing.T, resource map[string]any, layers ...Layer) map[string]any {
	t.Helper()
	out, err := ApplySettings(resource, layers)
	if err != nil {
		t.Fatal(err)
	}
	var parsed map[string]any
	if err := json.Unmarshal([]byte(out["content"].(string)), &parsed); err != nil {
		t.Fatalf("the merged file is not JSON: %v", err)
	}
	return parsed
}

func TestASettingBeatsTheModulesDefault(t *testing.T) {
	// The whole rule. A setting is a statement about that key made deliberately; the default was
	// only ever what to do in the absence of one. So there is nothing to resolve.
	got := merged(t, file(`{"port":8080,"log":"info"}`),
		Layer{From: "node", Values: map[string]any{"port": 9090.0}})

	if got["port"] != 9090.0 {
		t.Errorf("port is %v; the setting should have won", got["port"])
	}
	if got["log"] != "info" {
		t.Errorf("log is %v; a key nobody set should keep the module's value", got["log"])
	}
}

func TestUpstreamKeepsTheKeysNobodySet(t *testing.T) {
	// The point of merging rather than replacing: the module can change its half freely and only
	// the keys somebody actually cares about are pinned.
	got := merged(t, file(`{"port":8080,"log":"info","workers":4}`),
		Layer{From: "node", Values: map[string]any{"log": "debug"}})

	if got["port"] != 8080.0 || got["workers"] != 4.0 {
		t.Errorf("the module's other keys did not survive: %v", got)
	}
}

func TestTheNodeBeatsTheMesh(t *testing.T) {
	// Two layers, in order. A node that differs is expressed by differing, rather than by
	// repeating everything the rest of the mesh already says.
	got := merged(t, file(`{"log":"info"}`),
		Layer{From: "mesh", Values: map[string]any{"log": "warn", "workers": 8.0}},
		Layer{From: "node", Values: map[string]any{"log": "debug"}})

	if got["log"] != "debug" {
		t.Errorf("log is %v; the node's setting should have won", got["log"])
	}
	if got["workers"] != 8.0 {
		t.Errorf("workers is %v; a mesh-wide setting the node did not touch should stand", got["workers"])
	}
}

func TestNestedBlocksMergeRatherThanReplace(t *testing.T) {
	// Setting one field of a block must not delete its siblings, or every setting would have to
	// restate the whole block and would then pin all of it against upstream.
	got := merged(t, file(`{"http":{"gzip":"off","timeout":30,"port":80}}`),
		Layer{From: "node", Values: map[string]any{
			"http": map[string]any{"gzip": "on"}}})

	block := got["http"].(map[string]any)
	if block["gzip"] != "on" {
		t.Errorf("gzip is %v", block["gzip"])
	}
	if block["timeout"] != 30.0 || block["port"] != 80.0 {
		t.Errorf("the block's other fields were lost: %v", block)
	}
}

func TestAListIsReplacedWholeNotMerged(t *testing.T) {
	// A list that merged element-wise could neither be shortened nor reordered, and there is no
	// correct guess about which element is "the same one".
	got := merged(t, file(`{"hosts":["a","b","c"]}`),
		Layer{From: "node", Values: map[string]any{"hosts": []any{"x"}}})

	hosts := got["hosts"].([]any)
	if len(hosts) != 1 || hosts[0] != "x" {
		t.Errorf("hosts is %v; a list is replaced whole", hosts)
	}
}

func TestAProtectedKeyIsRefusedNotIgnored(t *testing.T) {
	// A setting quietly dropped is somebody believing they changed something. Refusing says so
	// while they are looking at it.
	_, err := ApplySettings(file(`{"socket":"/run/thing.sock","log":"info"}`, "socket"),
		[]Layer{{From: "node", Values: map[string]any{"socket": "/tmp/mine.sock"}}})
	if err == nil {
		t.Fatal("a protected key was overridden")
	}
	if !strings.Contains(err.Error(), "socket") || !strings.Contains(err.Error(), "not settable") {
		t.Errorf("the refusal does not say which key or why: %v", err)
	}
}

func TestSettingsAroundAProtectedKeyStillApply(t *testing.T) {
	got := merged(t, file(`{"socket":"/run/thing.sock","log":"info"}`, "socket"),
		Layer{From: "node", Values: map[string]any{"log": "debug"}})
	if got["log"] != "debug" {
		t.Errorf("log is %v", got["log"])
	}
}

func TestTheSameSettingsAlwaysProduceTheSameBytes(t *testing.T) {
	// A file whose lines move for no reason makes every reconcile look like a change, and a
	// service reflecting it would restart for ever.
	//
	// Note what this defends: Go's JSON encoder sorts map keys, so the stability comes from the
	// standard library and this passes with the merging removed. It is worth keeping as the thing
	// that would catch a move to an encoder that does not sort — but it is not evidence about the
	// code below it, and it was checked.
	resource := file(`{"b":2,"a":1,"c":3}`)
	layer := Layer{From: "node", Values: map[string]any{"z": 26.0, "a": 100.0}}

	first, err := ApplySettings(resource, []Layer{layer})
	if err != nil {
		t.Fatal(err)
	}
	for i := 0; i < 5; i++ {
		again, err := ApplySettings(resource, []Layer{layer})
		if err != nil {
			t.Fatal(err)
		}
		if again["content"] != first["content"] {
			t.Fatal("the same settings produced different bytes")
		}
	}
}

func TestAFileThatDoesNotMergeIsLeftAlone(t *testing.T) {
	plain := map[string]any{"id": "conf", "type": "file", "path": "/etc/thing",
		"content": "not structured at all\n"}
	out, err := ApplySettings(plain, []Layer{{From: "node", Values: map[string]any{"x": 1}}})
	if err != nil {
		t.Fatal(err)
	}
	if out["content"] != "not structured at all\n" {
		t.Errorf("a file with no merge rule was changed: %v", out["content"])
	}
}

func TestSettingsThatReachNothingAreNamed(t *testing.T) {
	// Somebody who misspells a module, or sets a key on one with nothing mergeable, has changed
	// nothing — and would otherwise find out by the machine not behaving differently, which is
	// the slowest way there is.
	m := Manifest{Module: "thing", Resources: []map[string]any{
		{"id": "conf", "type": "file", "path": "/etc/thing", "content": "plain"},
	}}
	unused := UnusedSettings(m, []Layer{{From: "node", Values: map[string]any{"port": 1}}})
	if len(unused) != 1 || !strings.Contains(unused[0], "no file to merge it into") {
		t.Errorf("settings that reached nothing were not named: %v", unused)
	}
}

func TestContentThatIsNotJSONIsRefusedWhereSomebodyIsLooking(t *testing.T) {
	// Rather than on the machine, at apply time, as a file the program cannot read.
	_, err := ApplySettings(file(`this is not json`), nil)
	if err == nil {
		t.Fatal("a module claiming to merge as JSON shipped something else and was accepted")
	}
}