package fejkdata

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"reflect"
	"regexp"
	"slices"
	"strings"
	"testing"
)

// TestList pins the discoverable paths: every category, its dotted fields, and
// folder segments — descending transparently through single-variant choices.
func TestList(t *testing.T) {
	dir := writeData(t, map[string]string{
		"person":   `{"format":"{first} {last}","first":"A","last":"B"}`,
		"word":     `["x", "y"]`,
		"geo/city": `"Z"`,
		// A bound {/path} reference is a render edge, not an addressable field.
		"greeting": `{"format":"hej {/person.first} and {own}","own":"x"}`,
		// Only the fields every variant carries are addressable, so "extra" is not.
		"coin": `[{"format":"{code}","code":"A","name":"Aa"},{"format":"{code}","code":"B","name":"Bb","extra":"x"}]`,
	})
	got := newGenerator(t, dir, WithSeed(1)).List()
	want := []string{"coin", "coin.code", "coin.name", "geo.city", "greeting", "greeting.own", "person", "person.first", "person.last", "word"}
	if !reflect.DeepEqual(got, want) {
		t.Fatalf("List() = %v, want %v", got, want)
	}
}

// writeData builds a temp data directory from a map of relative path (without
// ".json") -> file content, creating parent folders as needed. The directory's
// name carries no meaning anymore, so callers pick any layout they like —
// including nested folders, which become dot-path segments.
func writeData(t *testing.T, files map[string]string) string {
	t.Helper()
	dir := t.TempDir()
	for name, content := range files {
		p := filepath.Join(dir, name+".json")
		if err := os.MkdirAll(filepath.Dir(p), 0o755); err != nil {
			t.Fatal(err)
		}
		if err := os.WriteFile(p, []byte(content), 0o644); err != nil {
			t.Fatal(err)
		}
	}
	return dir
}

func TestNewLoadsAnyDirName(t *testing.T) {
	// No locale tag required: a directory named anything loads fine.
	dir := writeData(t, map[string]string{"greeting": `["hej", "hallå"]`})
	f := newGenerator(t, dir, WithSeed(1))
	if got := fake(t, f, "greeting"); got != "hej" && got != "hallå" {
		t.Fatalf("greeting = %q, want hej or hallå", got)
	}
}

func TestNewEmptyDirErrors(t *testing.T) {
	if _, err := New(WithoutShippedData(), WithDataPath(writeData(t, nil))); err == nil {
		t.Fatal("New(empty dir) = nil error")
	}
}

// TestFoldersBecomeDotPaths checks the core of the new model: a subfolder is a
// namespace, so data/<loc>/person.json is reachable as "<loc>.person".
func TestFoldersBecomeDotPaths(t *testing.T) {
	dir := writeData(t, map[string]string{
		"sv_SE/greeting": `"hej"`,
		"en_US/greeting": `"hi"`,
	})
	f := newGenerator(t, dir, WithSeed(1))
	if got := fake(t, f, "sv_SE.greeting"); got != "hej" {
		t.Fatalf("sv_SE.greeting = %q, want hej", got)
	}
	if got := fake(t, f, "en_US.greeting"); got != "hi" {
		t.Fatalf("en_US.greeting = %q, want hi", got)
	}
}

// TestNestedFoldersAndJSON crosses both nesting kinds in one dot path: folders
// a/b/c, then deep JSON fields inside the file at the end of that path.
func TestNestedFoldersAndJSON(t *testing.T) {
	dir := writeData(t, map[string]string{
		"a/b/c/thing": `{"format":"{x}","x":{"format":"{y}","y":{"format":"{z}","z":"leaf"}}}`,
	})
	f := newGenerator(t, dir, WithSeed(1))
	// Folders a.b.c, file thing, then JSON fields x.y.z — one continuous path.
	if got := fake(t, f, "a.b.c.thing.x.y.z"); got != "leaf" {
		t.Fatalf("a.b.c.thing.x.y.z = %q, want leaf", got)
	}
	// Rendering the file resolves the same chain top-down.
	if got := fake(t, f, "a.b.c.thing"); got != "leaf" {
		t.Fatalf("a.b.c.thing = %q, want leaf", got)
	}
}

func TestRenderingAFolderErrors(t *testing.T) {
	dir := writeData(t, map[string]string{"sv_SE/greeting": `"hej"`})
	f := newGenerator(t, dir, WithSeed(1))
	if _, err := f.Fake("sv_SE"); err == nil {
		t.Fatal("Fake(folder) = nil error, want a not-a-value error")
	}
}

// TestMultiPathLastWins loads two dirs; on a name clash the later dir wins, and
// non-clashing entries from both are reachable (data combines).
func TestMultiPathLastWins(t *testing.T) {
	a := writeData(t, map[string]string{"greeting": `"from-a"`, "only-a": `"a"`})
	b := writeData(t, map[string]string{"greeting": `"from-b"`, "only-b": `"b"`})
	f := newGeneratorN(t, []string{a, b}, WithSeed(1))
	if got := fake(t, f, "greeting"); got != "from-b" {
		t.Fatalf("greeting = %q, want from-b (last loaded wins)", got)
	}
	if got := fake(t, f, "only-a"); got != "a" {
		t.Fatalf("only-a = %q, want a", got)
	}
	if got := fake(t, f, "only-b"); got != "b" {
		t.Fatalf("only-b = %q, want b", got)
	}
}

// TestMultiPathMergesFolders checks that clashing folders merge by their
// children rather than replacing wholesale: each dir adds a file to sv_SE, and
// a per-file clash inside still resolves last-wins.
func TestMultiPathMergesFolders(t *testing.T) {
	a := writeData(t, map[string]string{"sv_SE/person": `"from-a"`, "sv_SE/shared": `"a"`})
	b := writeData(t, map[string]string{"sv_SE/company": `"from-b"`, "sv_SE/shared": `"b"`})
	f := newGeneratorN(t, []string{a, b}, WithSeed(1))
	if got := fake(t, f, "sv_SE.person"); got != "from-a" {
		t.Fatalf("sv_SE.person = %q, want from-a (folder merged, not replaced)", got)
	}
	if got := fake(t, f, "sv_SE.company"); got != "from-b" {
		t.Fatalf("sv_SE.company = %q, want from-b", got)
	}
	if got := fake(t, f, "sv_SE.shared"); got != "b" {
		t.Fatalf("sv_SE.shared = %q, want b (last loaded wins)", got)
	}
}

// TestListedPathsAllRender is the contract between List and Fake over the shipped
// tree: everything List advertises renders, every time, and the sub-fields the
// README advertises are discoverable.
func TestListedPathsAllRender(t *testing.T) {
	f := newGenerator(t, "data", WithSeed(4))
	paths := f.List()
	for _, p := range paths {
		for i := 0; i < 20; i++ {
			if _, err := f.Fake(p); err != nil {
				t.Fatalf("Fake(%q) = %v, but List() advertises it", p, err)
			}
		}
	}
	for _, p := range []string{"misc.car.maker", "misc.country.alpha2", "misc.currency.symbol", "misc.httpstatus.code", "misc.mimetype.ext"} {
		if !slices.Contains(paths, p) {
			t.Errorf("List() omits %q, which the README advertises and Fake renders", p)
		}
	}
}

// TestHiddenEntriesAreSkipped keeps a data directory usable when it is also a
// checkout or an editor workspace: a dot-prefixed entry is not data, and a folder
// carrying no JSON never contributed a namespace, so neither may fail the load.
func TestHiddenEntriesAreSkipped(t *testing.T) {
	dir := writeData(t, map[string]string{
		"cat":              `"V"`,
		".git/HEAD":        `"ignored"`,
		".hidden":          `"ignored"`,
		"empty.folder/doc": `"ignored"`,
	})
	if err := os.Rename(filepath.Join(dir, "empty.folder", "doc.json"), filepath.Join(dir, "empty.folder", "doc.txt")); err != nil {
		t.Fatal(err)
	}
	f := newGenerator(t, dir, WithSeed(1))
	if got := fake(t, f, "cat"); got != "V" {
		t.Fatalf("cat = %q, want V", got)
	}
	for _, p := range f.List() {
		if strings.HasPrefix(p, ".") || strings.Contains(p, "empty.folder") {
			t.Errorf("List() advertises %q, which is not data", p)
		}
	}
}

func TestRepeatProductAlongAPathIsCapped(t *testing.T) {
	for name, files := range map[string]map[string]string{
		"nested": {"cat": `{"format":"{a}","repeat":2048,"a":{"format":"{b}","repeat":2048,"b":"x"}}`},
		"through a reference": {
			"a": `{"format":"{/b}","repeat":2048}`,
			"b": `{"format":"x","repeat":2048}`,
		},
	} {
		_, err := New(WithoutShippedData(), WithDataPath(writeData(t, files)))
		if err == nil || !strings.Contains(err.Error(), "repeat") || !strings.Contains(err.Error(), "1048576") {
			t.Errorf("%s: New = %v, want the repeat product rejected naming the maximum", name, err)
		}
	}
	if _, err := New(WithoutShippedData(), WithDataPath(writeData(t, map[string]string{
		"cat": `{"format":"{a}{c}","repeat":1024,"a":{"format":"{b}","repeat":1024,"b":"x"},"c":{"format":"y","repeat":1024}}`,
	}))); err != nil {
		t.Errorf("New = %v, want 1024 x 1024 along one path accepted", err)
	}
}

func TestNewErrors(t *testing.T) {
	// Pointing New at a file (not a directory) fails.
	file := filepath.Join(t.TempDir(), "xx_XX")
	if err := os.WriteFile(file, []byte("{}"), 0o644); err != nil {
		t.Fatal(err)
	}
	if _, err := New(WithoutShippedData(), WithDataPath(file)); err == nil {
		t.Error("New(file) = nil error, want not-a-directory error")
	}
	// Invalid JSON in a category file fails.
	if _, err := New(WithoutShippedData(), WithDataPath(writeData(t, map[string]string{"broken": `{ not json`}))); err == nil {
		t.Error("New(invalid JSON) = nil error")
	}
	// An option that cannot take effect, and a category or folder no dot path can
	// reach, are mistakes New must name rather than accept and ignore.
	rejected := map[string]struct {
		files map[string]string
		want  string
	}{
		"separator without repeat": {
			map[string]string{"a": `{"format":"{x}","x":"1","separator":","}`},
			"has no effect without a repeat above 1",
		},
		"separator with an explicit repeat of 1": {
			map[string]string{"a": `{"format":"{x}","x":"1","separator":","}`},
			"has no effect without a repeat above 1",
		},
		"weight outside a choice": {
			map[string]string{"a": `{"format":"x","weight":5}`},
			"weight only skews a choice's items",
		},
		"non-numeric weight outside a choice": {
			map[string]string{"a": `{"format":"x","weight":"bad"}`},
			"weight only skews a choice's items",
		},
		"weight used as a field": {
			map[string]string{"a": `{"format":"{name} {weight}kg","name":"Anvil","weight":["7"]}`},
			"can never be a field",
		},
		"an option name used as a token": {
			map[string]string{"a": `"{weight}"`},
			`"weight" is an option and can never be a field`,
		},
		"category name with a dot": {
			map[string]string{"a.b": `"1"`},
			`category "a.b" contains "."`,
		},
		"folder name with a dot": {
			map[string]string{"a.b/cat": `"1"`},
			`/a.b: folder "a.b" contains "."`,
		},
		// The token grammar reserves three more characters. A name carrying one
		// still resolves by dot path, but no format can name it, so it is rejected
		// where it is authored rather than at the token that cannot reach it.
		"field name with a pipe": {
			map[string]string{"a": `{"format":"{x}","x":"1","b|c":"2"}`},
			`field "b|c" contains "|"`,
		},
		"field name with a paren": {
			map[string]string{"a": `{"format":"{x}","x":"1","b(c":"2"}`},
			`field "b(c" contains "("`,
		},
		"field name with a closing brace": {
			map[string]string{"a": `{"format":"{x}","x":"1","b}c":"2"}`},
			`field "b}c" contains "}"`,
		},
		"category name with a pipe": {
			map[string]string{"a|b": `"1"`},
			`category "a|b" contains "|"`,
		},
		// A bracket is not a token-grammar character, but the CLI reads an argument
		// starting with [ as a JSON array, so a name carrying one would be misread.
		"field name with a bracket": {
			map[string]string{"a": `{"format":"{x}","x":"1","b[c":"2"}`},
			`field "b[c" contains "["`,
		},
		"category name with a bracket": {
			map[string]string{"[abc]": `"1"`},
			`category "[abc]" contains "["`,
		},
		// An empty name is not a path segment, so List never offered it — while a
		// bare {}, a trailing dot in Fake("a.") and a {/a.} reference all reached
		// it. The engine accepted spellings it would never advertise.
		"empty field name": {
			map[string]string{"a": `{"format":"[{}]","":"VALUE"}`},
			`field "" is empty`,
		},
		"folder name with a paren": {
			map[string]string{"a(b/cat": `"1"`},
			`folder "a(b" contains "("`,
		},
		// A repeated arm skews an alternation, which weight is the spelling for.
		"repeated alternation arm": {
			map[string]string{"a": `{"format":"{x|x}","x":"1"}`},
			`arm "x" is repeated`,
		},
		"repeated arm among others": {
			map[string]string{"a": `{"format":"{x|y|x}","x":"1","y":"2"}`},
			`arm "x" is repeated`,
		},
		"repeated path arm": {
			map[string]string{"a": `{"format":"{p.v|p.v}","p":{"format":"{v}","v":"1"}}`},
			`arm "p.v" is repeated`,
		},
		// A reference arm is the only kind that reaches the repeat check by passing
		// the per-arm checks rather than falling through them.
		"repeated reference arm": {
			map[string]string{"a": `"x"`, "b": `"{/a|/a}"`},
			`arm "/a" is repeated`,
		},
		// An arm that is broken on its own terms is reported as that, not as a
		// repeat: the repeat is a consequence of the real mistake.
		"repeated arm with no path": {
			map[string]string{"a": `"{/|/}"`},
			"reference has no path",
		},
		// No field can be named "", so the token is told that rather than sent to
		// name one — the fix "no field" points at is itself a load error.
		"repeated empty arm": {
			map[string]string{"a": `"{|}"`},
			"a name is never empty",
		},
		"bare empty token": {
			map[string]string{"a": `{"format":"[{}]","x":"1"}`},
			"a name is never empty",
		},
	}
	for name, c := range rejected {
		_, err := New(WithoutShippedData(), WithDataPath(writeData(t, c.files)))
		if err == nil {
			t.Errorf("%s: New = nil error, want it rejected at load", name)
			continue
		}
		if !strings.Contains(err.Error(), c.want) {
			t.Errorf("%s: New = %v, want it to mention %q", name, err, c.want)
		}
	}
	// Data that works today must keep working, and stay reachable.
	accepted := map[string]struct {
		files map[string]string
		path  string
		want  string
	}{
		"option name as a field":     {map[string]string{"a": `{"format":"{name} {Weight}kg","name":"Anvil","Weight":"7"}`}, "a", "Anvil 7kg"},
		"format spelling as a field": {map[string]string{"a": `{"format":"{Format}","Format":"PDF"}`}, "a", "PDF"},
		"hyphenated field":           {map[string]string{"a": `{"format":"{x-y}","x-y":"1"}`}, "a.x-y", "1"},
		"category named Format":      {map[string]string{"Format": `"1"`}, "Format", "1"},
		"folder named Repeat":        {map[string]string{"Repeat/cat": `"1"`}, "Repeat.cat", "1"},
		"field with a closing paren": {map[string]string{"a": `{"format":"{b)c}","b)c":"2"}`}, "a", "2"},
		"repeat without a separator": {map[string]string{"a": `{"format":"{x}","repeat":3,"x":"1"}`}, "a", "111"},
		// One name in two separate tokens is two independent draws, not a repeated
		// arm; only a repeat within one alternation is rejected.
		"one name in two tokens": {map[string]string{"a": `{"format":"{x}{x}","x":"1"}`}, "a", "11"},
	}
	for name, c := range accepted {
		f, err := New(WithoutShippedData(), WithDataPath(writeData(t, c.files)))
		if err != nil {
			t.Errorf("%s: New = %v, want it accepted", name, err)
			continue
		}
		if got, err := f.Fake(c.path); err != nil || got != c.want {
			t.Errorf("%s: Fake(%q) = %q, %v, want %q", name, c.path, got, err, c.want)
		}
	}
}

func TestCategoryRootShapes(t *testing.T) {
	dir := writeData(t, map[string]string{
		"obj": `"{digits(2)}"`, // object root
		"lit": `"hello"`,       // bare-string root
	})
	f := newGenerator(t, dir, WithSeed(1))
	if got := fake(t, f, "obj"); !regexp.MustCompile(`^\d\d$`).MatchString(got) {
		t.Errorf("object-root category = %q, want two digits", got)
	}
	if got := fake(t, f, "lit"); got != "hello" {
		t.Errorf("string-root category = %q, want hello", got)
	}
}

func TestLongStringList(t *testing.T) {
	const n = 2000
	names := make([]string, n)
	for i := range names {
		names[i] = fmt.Sprintf("name-%04d", i)
	}
	list, err := json.Marshal(names)
	if err != nil {
		t.Fatal(err)
	}
	f := newGenerator(t, writeData(t, map[string]string{"name": string(list)}), WithSeed(1))

	valid := map[string]bool{}
	for _, v := range names {
		valid[v] = true
	}
	seen := map[string]bool{}
	for i := 0; i < 20000; i++ {
		v := fake(t, f, "name")
		if !valid[v] {
			t.Fatalf("got %q, not in the list", v)
		}
		seen[v] = true
	}
	if len(seen) < n*8/10 {
		t.Fatalf("only %d/%d distinct values seen; selection looks skewed", len(seen), n)
	}
}