package validation

import (
	"context"
	"errors"
	"os"
	"path/filepath"
	"strings"
	"testing"
	"time"
)

func TestResolveDestinationClassifiesCommittedPaths(t *testing.T) {
	repository := newTreeRepository(t)
	writeTreeFile(t, repository, "README.md", []byte("root\n"))
	writeTreeFile(t, repository, "docs/page.md", []byte("source\n"))
	writeTreeFile(t, repository, "docs/target.md", []byte("target\n"))
	writeTreeFile(t, repository, "docs/nested/item.txt", []byte("nested\n"))
	writeTreeFile(t, repository, "docs/dir/item.txt", []byte("directory\n"))
	for name, target := range map[string]string{
		"docs/inside":      "target.md",
		"docs/through-dir": "nested",
		"docs/outside":     "../../neighbor/file",
		"docs/absolute":    "/outside/file",
		"docs/dangling":    "missing-target",
		"docs/cycle-a":     "cycle-b",
		"docs/cycle-b":     "cycle-a",
	} {
		if err := os.Symlink(target, filepath.Join(repository, filepath.FromSlash(name))); err != nil {
			t.Fatal(err)
		}
	}
	submoduleSource := newTreeRepository(t)
	writeTreeFile(t, submoduleSource, "sub.txt", []byte("submodule\n"))
	gitTree(t, submoduleSource, "add", "--all")
	gitTree(t, submoduleSource, "commit", "-m", "create submodule source")
	submoduleOID := strings.TrimSpace(gitTree(t, submoduleSource, "rev-parse", "HEAD"))
	gitTree(t, repository, "add", "--all")
	gitTree(t, repository, "update-index", "--add", "--cacheinfo", "160000,"+submoduleOID+",docs/submodule")
	gitTree(t, repository, "commit", "-m", "capture destination fixtures")
	commit := strings.TrimSpace(gitTree(t, repository, "rev-parse", "HEAD"))
	tree, err := ReadCandidateTree(context.Background(), repository, commit)
	if err != nil {
		t.Fatal(err)
	}
	if err := os.Remove(filepath.Join(repository, "docs", "inside")); err != nil {
		t.Fatal(err)
	}
	if err := os.Symlink("../../neighbor/file", filepath.Join(repository, "docs", "inside")); err != nil {
		t.Fatal(err)
	}

	cases := []struct {
		name        string
		source      string
		destination string
		kind        DestinationKind
		path        string
	}{
		{name: "relative file", source: "docs/page.md", destination: "target.md", kind: DestinationEntry, path: "docs/target.md"},
		{name: "parent traversal inside root", source: "docs/page.md", destination: "../README.md", kind: DestinationEntry, path: "README.md"},
		{name: "outside root", source: "docs/page.md", destination: "../../neighbor/file", kind: DestinationOutsideCheckout, path: "../neighbor/file"},
		{name: "repository root directory", source: "docs/page.md", destination: "..", kind: DestinationDirectory, path: "."},
		{name: "directory", source: "docs/page.md", destination: "dir", kind: DestinationDirectory, path: "docs/dir"},
		{name: "symlink to file", source: "docs/page.md", destination: "inside", kind: DestinationEntry, path: "docs/target.md"},
		{name: "symlinked directory", source: "docs/page.md", destination: "through-dir/item.txt", kind: DestinationEntry, path: "docs/nested/item.txt"},
		{name: "absolute symlink", source: "docs/page.md", destination: "absolute", kind: DestinationOutsideCheckout, path: "/outside/file"},
		{name: "missing entry", source: "docs/page.md", destination: "missing", kind: DestinationMissing, path: "docs/missing"},
		{name: "dangling symlink", source: "docs/page.md", destination: "dangling", kind: DestinationMissing, path: "docs/missing-target"},
		{name: "symlink cycle", source: "docs/page.md", destination: "cycle-a", kind: DestinationSymlinkCycle, path: "docs/cycle-a"},
		{name: "submodule contents", source: "docs/page.md", destination: "submodule/child", kind: DestinationSubmodule, path: "docs/submodule/child"},
	}
	for _, test := range cases {
		t.Run(test.name, func(t *testing.T) {
			got, err := tree.ResolveDestination(context.Background(), test.source, test.destination)
			if err != nil {
				t.Fatalf("ResolveDestination() error = %v", err)
			}
			if got.Kind != test.kind || got.Path != test.path {
				t.Fatalf("ResolveDestination() = %#v, want kind %q path %q", got, test.kind, test.path)
			}
		})
	}
}

func TestResolveDestinationHandlesExpandingCyclesAndRepeatedLinks(t *testing.T) {
	repository := newTreeRepository(t)
	writeTreeFile(t, repository, "README.md", []byte("source\n"))
	for name, target := range map[string]string{
		"direct":   "direct/child",
		"mutual-a": "mutual-b/child",
		"mutual-b": "mutual-a/child",
		"alias":    ".",
	} {
		if err := os.Symlink(target, filepath.Join(repository, name)); err != nil {
			t.Fatal(err)
		}
	}
	gitTree(t, repository, "add", "--all")
	gitTree(t, repository, "commit", "-m", "capture recursive links")
	tree, err := ReadCandidateTree(t.Context(), repository, strings.TrimSpace(gitTree(t, repository, "rev-parse", "HEAD")))
	if err != nil {
		t.Fatal(err)
	}
	for _, test := range []struct {
		destination string
		kind        DestinationKind
	}{
		{"direct", DestinationSymlinkCycle},
		{"mutual-a", DestinationSymlinkCycle},
		{"alias/alias/README.md", DestinationEntry},
	} {
		t.Run(test.destination, func(t *testing.T) {
			type result struct {
				destination Destination
				err         error
			}
			done := make(chan result, 1)
			ctx, cancel := context.WithTimeout(t.Context(), time.Second)
			defer cancel()
			go func() {
				destination, err := tree.ResolveDestination(ctx, "README.md", test.destination)
				done <- result{destination, err}
			}()
			select {
			case got := <-done:
				if got.err != nil || got.destination.Kind != test.kind {
					t.Fatalf("resolution = %#v, %v; want %s", got.destination, got.err, test.kind)
				}
				if test.kind == DestinationEntry && got.destination.Path != "README.md" {
					t.Fatalf("finite repeated link resolved to %q", got.destination.Path)
				}
			case <-ctx.Done():
				t.Fatal("symlink resolution did not finish")
			}
		})
	}
	ctx, cancel := context.WithCancel(t.Context())
	cancel()
	if _, err := tree.ResolveDestination(ctx, "README.md", "alias/README.md"); !errors.Is(err, context.Canceled) {
		t.Fatalf("canceled resolution error = %v", err)
	}
}

func TestResolveDestinationIgnoresNeighboringFiles(t *testing.T) {
	repository := newTreeRepository(t)
	writeTreeFile(t, repository, "docs/page.md", []byte("source\n"))
	if err := os.Symlink("../../neighbor/file", filepath.Join(repository, "docs", "outside")); err != nil {
		t.Fatal(err)
	}
	gitTree(t, repository, "add", "--all")
	gitTree(t, repository, "commit", "-m", "capture outside link")
	commit := strings.TrimSpace(gitTree(t, repository, "rev-parse", "HEAD"))
	tree, err := ReadCandidateTree(context.Background(), repository, commit)
	if err != nil {
		t.Fatal(err)
	}
	gotWithoutNeighbor, err := tree.ResolveDestination(context.Background(), "docs/page.md", "outside")
	if err != nil {
		t.Fatal(err)
	}
	neighbor := filepath.Join(filepath.Dir(repository), "neighbor", "file")
	if err := os.MkdirAll(filepath.Dir(neighbor), 0o755); err != nil {
		t.Fatal(err)
	}
	if err := os.WriteFile(neighbor, []byte("outside source\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	gotWithNeighbor, err := tree.ResolveDestination(context.Background(), "docs/page.md", "outside")
	if err != nil {
		t.Fatal(err)
	}
	if gotWithNeighbor != gotWithoutNeighbor || gotWithNeighbor.Kind != DestinationOutsideCheckout {
		t.Fatalf("neighbor changed resolution: absent=%#v present=%#v", gotWithoutNeighbor, gotWithNeighbor)
	}
}