package apply

import (
	"context"
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"testing"

	"github.com/novox/mesh-host/internal/store"
)

// A filled write is one file, not an apply: it asks no container runtime, and judges where nothing is placed
// (issue 339) with the roots the last apply read, falling back to the runtimes' configuration files when no apply
// has read them yet (novox/hq issue 1138). These tests set the package's runtimeRoots and AskRuntimes, so none
// runs in parallel with another that reads or sets them, and each restores what it changed.

// setRuntimeRoots makes runtimeDataRoots answer roots, as if an apply had just read them (or, with nil, as if none
// ever had), restoring what a test before it left there once this one is done.
func setRuntimeRoots(t *testing.T, roots []string) {
	t.Helper()
	runtimeRootsMu.Lock()
	before := runtimeRoots
	runtimeRoots = roots
	runtimeRootsMu.Unlock()
	t.Cleanup(func() {
		runtimeRootsMu.Lock()
		runtimeRoots = before
		runtimeRootsMu.Unlock()
	})
}

// askNoRuntime makes AskRuntimes record the name of every runtime it is asked for, answering as one that is not
// running does (nothing, no error): were it consulted, that is what would say so. Restored once the test is done.
func askNoRuntime(t *testing.T, asked *[]string) {
	t.Helper()
	before := AskRuntimes
	AskRuntimes = func(_ context.Context, name string, _ ...string) (string, error) {
		*asked = append(*asked, name)
		return "", nil
	}
	t.Cleanup(func() { AskRuntimes = before })
}

// aRuntimeConfig points the runtimes' configuration at a fresh, unmounted root below a temp directory, restoring
// the engine's real configuration once the test is done.
func aRuntimeConfig(t *testing.T) (dir, root string) {
	t.Helper()
	dir = t.TempDir()
	root = filepath.Join(dir, "docker")
	daemon := filepath.Join(dir, "daemon.json")
	if err := os.WriteFile(daemon, []byte(`{"data-root":"`+root+`"}`), 0o644); err != nil {
		t.Fatal(err)
	}
	before := runtimeConfigs
	runtimeConfigs = runtimeFiles{daemonJSON: daemon, storageConf: filepath.Join(dir, "none.conf")}
	t.Cleanup(func() { runtimeConfigs = before })
	return dir, root
}

// refusedAsPlacement fails the test unless err is a PlacementRefusedError.
func refusedAsPlacement(t *testing.T, err error) {
	t.Helper()
	var refusal *PlacementRefusedError
	if err == nil || !errors.As(err, &refusal) {
		t.Fatalf("a filled file below a refused runtime root was not refused: %v", err)
	}
}

// 1138/AC1: a filled write asks no runtime, and judges with the roots the last apply read.
func TestAFilledWriteAsksNoRuntimeAndUsesTheLastApplysRoots(t *testing.T) {
	root := filepath.Join(t.TempDir(), "docker-root")
	setRuntimeRoots(t, []string{root}) // as if an apply had just read it

	var asked []string
	askNoRuntime(t, &asked)

	path := filepath.Join(root, "app.conf")
	d := filledDecl(t, path, `"content":"","owner-at-runtime":"owned"`, "")
	_, _, err := WriteFilled(context.Background(), archHost(t), d, store.State{}, path, []byte("x\n"), noServices,
		nil, nil, nil)

	refusedAsPlacement(t, err)
	if len(asked) != 0 {
		t.Errorf("a filled write asked the container runtimes: %v", asked)
	}
}

// 1138/AC2: given a real apply that read a runtime data root, a filled write below it is refused as today, with
// no apply run again in between.
func TestAFilledWriteBelowARootARealApplyReadIsRefused(t *testing.T) {
	dir, root := aRuntimeConfig(t)
	t.Cleanup(func() {
		runtimeRootsMu.Lock()
		runtimeRoots = nil
		runtimeRootsMu.Unlock()
	})

	// A full apply of something unrelated reads the runtimes' configuration once, at its start.
	elsewhere := filepath.Join(dir, "elsewhere.conf")
	if _, _, err := Apply(context.Background(), archHost(t), declare(t,
		fmt.Sprintf(`{"id":"m.other","type":"file","path":%q,"content":"x\n"}`, elsewhere)),
		store.State{}, store.OriginDeclared, noServices, nil, nil); err != nil {
		t.Fatal(err)
	}

	// A filled write below the runtime's root, with no apply run since, is still refused.
	path := filepath.Join(root, "sub", "app.conf")
	d := filledDecl(t, path, `"content":"","owner-at-runtime":"owned"`, "")
	_, _, err := WriteFilled(context.Background(), archHost(t), d, store.State{}, path, []byte("x\n"), noServices,
		nil, nil, nil)
	refusedAsPlacement(t, err)
}

// 1138/AC3: with no apply having read the roots yet, a filled write judges by the runtimes' configuration files,
// asking no runtime.
func TestAFilledWriteWithNoApplyYetUsesTheRuntimesConfigFiles(t *testing.T) {
	setRuntimeRoots(t, nil) // no apply has read the roots yet
	_, root := aRuntimeConfig(t)

	var asked []string
	askNoRuntime(t, &asked)

	path := filepath.Join(root, "sub", "app.conf")
	d := filledDecl(t, path, `"content":"","owner-at-runtime":"owned"`, "")
	_, _, err := WriteFilled(context.Background(), archHost(t), d, store.State{}, path, []byte("x\n"), noServices,
		nil, nil, nil)

	refusedAsPlacement(t, err)
	if len(asked) != 0 {
		t.Errorf("a filled write with no apply yet asked the container runtimes: %v", asked)
	}
}

// 1138/AC4: a full apply still asks each runtime once, at its start, whatever the number of files it writes.
func TestAFullApplyAsksEachRuntimeOnceRegardlessOfFileCount(t *testing.T) {
	dir := t.TempDir()
	var asked []string
	before := AskRuntimes
	AskRuntimes = func(_ context.Context, name string, _ ...string) (string, error) {
		asked = append(asked, name)
		return "", errors.New("not running in this test")
	}
	t.Cleanup(func() {
		AskRuntimes = before
		runtimeRootsMu.Lock()
		runtimeRoots = nil
		runtimeRootsMu.Unlock()
	})

	var resources []string
	for i := 0; i < 3; i++ {
		resources = append(resources, fmt.Sprintf(`{"id":"m.f%d","type":"file","path":%q,"content":"x\n"}`, i,
			filepath.Join(dir, fmt.Sprintf("f%d.conf", i))))
	}
	if _, _, err := Apply(context.Background(), archHost(t), declare(t, strings.Join(resources, ",")),
		store.State{}, store.OriginDeclared, noServices, nil, nil); err != nil {
		t.Fatal(err)
	}
	if got := count(asked, "docker"); got != 1 {
		t.Errorf("docker was asked %d times for one apply of 3 files; want 1: %v", got, asked)
	}
	if got := count(asked, "podman"); got != 1 {
		t.Errorf("podman was asked %d times for one apply of 3 files; want 1: %v", got, asked)
	}
}