package fejkdata

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

// writeFiles writes a data directory from a map of relative file name, extension
// included, to content.
func writeFiles(t *testing.T, files map[string]string) string {
	t.Helper()
	dir := t.TempDir()
	for name, content := range files {
		p := filepath.Join(dir, name)
		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
}

// geo is three linked tables: region <- municipality <- locality.
func geo() map[string]string {
	return map[string]string{
		"region.json":       `{"format":"{name}","rows":"region.tsv","key":"code","name":"name","weight":"population"}`,
		"region.tsv":        "code\tname\tpopulation\ttimezone\n01\tStockholms län\t2400000\tEurope/Stockholm\n12\tSkåne län\t1400000\tEurope/Stockholm\n14\tVästra Götalands län\t1750000\tEurope/Stockholm\n",
		"municipality.json": `{"format":"{name}","rows":"municipality.tsv","key":"code","name":"name","parent":"region","weight":"population"}`,
		"municipality.tsv":  "code\tname\tregion\tpopulation\n0180\tStockholm\t01\t980000\n0184\tSolna\t01\t85000\n1280\tMalmö\t12\t360000\n1281\tLund\t12\t130000\n1480\tGöteborg\t14\t590000\n",
		"locality.json":     `{"format":"{name}","rows":"locality.tsv","key":"code","name":"name","parent":"municipality"}`,
		"locality.tsv":      "code\tname\tmunicipality\nL1\tStockholm\t0180\nL2\tSolna\t0184\nL3\tMalmö\t1280\nL4\tLund\t1281\nL5\tGöteborg\t1480\nL6\tHisingen\t1480\nL7\tSandby\t1281\nL8\tSandby\t0184\n",
	}
}

var (
	municipalityOf = map[string]string{"L1": "0180", "L2": "0184", "L3": "1280", "L4": "1281", "L5": "1480", "L6": "1480", "L7": "1281", "L8": "0184"}
	regionOf       = map[string]string{"0180": "01", "0184": "01", "1280": "12", "1281": "12", "1480": "14"}
)

func with(files map[string]string, more map[string]string) map[string]string {
	out := map[string]string{}
	for k, v := range files {
		out[k] = v
	}
	for k, v := range more {
		out[k] = v
	}
	return out
}

func TestTableRendersRowsAndColumns(t *testing.T) {
	f := newGenerator(t, writeFiles(t, geo()), WithSeed(1))
	names := map[string]bool{"Stockholms län": true, "Skåne län": true, "Västra Götalands län": true}
	for i := 0; i < 50; i++ {
		if v := fake(t, f, "region"); !names[v] {
			t.Fatalf("region = %q, want a row's format", v)
		}
		if v := fake(t, f, "region.timezone"); v != "Europe/Stockholm" {
			t.Fatalf("region.timezone = %q", v)
		}
		if v := fake(t, f, "region.code"); v != "01" && v != "12" && v != "14" {
			t.Fatalf("region.code = %q", v)
		}
	}
	want := []string{
		"locality", "locality.code", "locality.municipality", "locality.name",
		"municipality", "municipality.code", "municipality.locality", "municipality.locality.code", "municipality.locality.municipality", "municipality.locality.name", "municipality.name", "municipality.population", "municipality.region",
		"region", "region.code", "region.municipality", "region.municipality.code", "region.municipality.locality", "region.municipality.locality.code", "region.municipality.locality.municipality", "region.municipality.locality.name", "region.municipality.name", "region.municipality.population", "region.municipality.region", "region.name", "region.population", "region.timezone",
	}
	if got := f.List(); !reflect.DeepEqual(got, want) {
		t.Fatalf("List() = %v\nwant %v", got, want)
	}
	r, err := f.FakeRecord("region")
	if err != nil {
		t.Fatal(err)
	}
	if r.CSVHeader() != "code,name,population,timezone" {
		t.Fatalf("CSVHeader = %q", r.CSVHeader())
	}
	line := strings.Split(r.CSVLine(), ",")
	if len(line) != 4 || !names[line[1]] || line[3] != "Europe/Stockholm" {
		t.Fatalf("CSVLine = %q, want one row's cells", r.CSVLine())
	}
	for _, c := range r.Columns() {
		if c.DataType != DataTypeString || c.Null {
			t.Fatalf("column %q is %s null=%v, want a string", c.Name, c.DataType, c.Null)
		}
	}
}

func TestTableWeightSkewsTheDraw(t *testing.T) {
	f := newGenerator(t, writeFiles(t, geo()), WithSeed(3))
	count := map[string]int{}
	for i := 0; i < 3000; i++ {
		count[fake(t, f, "region.code")]++
	}
	if count["01"] < 1200 || count["12"] > 900 {
		t.Fatalf("region draws %v, want weighted by population (01 ≈ 43%%, 12 ≈ 25%%)", count)
	}
	count = map[string]int{}
	for i := 0; i < 3000; i++ {
		count[fake(t, f, "region[01].municipality.code")]++
	}
	if count["0180"] < 2500 || count["0184"] == 0 || len(count) != 2 {
		t.Fatalf("municipality draws inside 01 %v, want Stockholm ≈ 92%% and Solna the rest", count)
	}
}

func TestTableCellsAreStringNodes(t *testing.T) {
	dir := writeFiles(t, map[string]string{
		"w.json":     `"x"`,
		"place.json": `{"format":"{zip} {name}","rows":"place.tsv","key":"name"}`,
		"place.tsv":  "name\tzip\ttag\nStockholm\t1{digits(2)} {digits(2)}\t{/w}\nTranås\t573 {digits(2)}\tplain\n",
	})
	f := newGenerator(t, dir, WithSeed(1))
	zip := regexp.MustCompile(`^(1\d\d \d\d Stockholm|573 \d\d Tranås)$`)
	for i := 0; i < 50; i++ {
		if v := fake(t, f, "place"); !zip.MatchString(v) {
			t.Fatalf("place = %q, want the cell's tokens expanded", v)
		}
	}
	if v := fake(t, f, "place[Stockholm].tag"); v != "x" {
		t.Fatalf("place[Stockholm].tag = %q, want the reference rendered", v)
	}
	bad := writeFiles(t, map[string]string{
		"place.json": `{"format":"{name}","rows":"place.tsv"}`,
		"place.tsv":  "name\tzip\nA\t{name}\nB\t2\n",
	})
	if _, err := New(WithoutShippedData(), WithDataPath(bad)); err == nil || !strings.Contains(err.Error(), "place.tsv") || !strings.Contains(err.Error(), `no field "name"`) {
		t.Fatalf("New = %v, want a cell reading a column refused, naming the file", err)
	}
}

func TestTableSelectsARowByKeyOrName(t *testing.T) {
	files := with(geo(), map[string]string{
		"city.json": `{"format":"{name}","rows":"city.tsv","key":"code","name":"name"}`,
		"city.tsv":  "code\tname\nSTL\tSt. Louis\nSPI\tSpringfield\n",
	})
	f := newGenerator(t, writeFiles(t, files), WithSeed(1))
	for path, want := range map[string]string{
		"region[12]":                               "Skåne län",
		"region[Skåne län].code":                   "12",
		"municipality[1281].locality[Sandby]":      "Sandby",
		"municipality[1281].locality[Sandby].code": "L7",
		"municipality[0184].locality[Sandby].code": "L8",
		"city[St. Louis].code":                     "STL",
	} {
		if got := fake(t, f, path); got != want {
			t.Errorf("Fake(%q) = %q, want %q", path, got, want)
		}
	}
	for path, want := range map[string]string{
		"region[99]":                    `"99"`,
		"locality[Sandby]":              "L7 L8",
		"region[12].code[1]":            "not a table",
		"region[]":                      "empty",
		"region[12":                     "]",
		"region[12].municipality[1480]": "not inside",
	} {
		if _, err := f.Fake(path); err == nil || !strings.Contains(err.Error(), want) {
			t.Errorf("Fake(%q) = %v, want an error mentioning %s", path, err, want)
		}
	}
	if v := fake(t, f, "municipality[0180].region"); v != "01" {
		t.Fatalf("municipality[0180].region = %q, want the link column's cell", v)
	}
	noKey := writeFiles(t, map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv"}`, "t.tsv": "a\nx\ny\n"})
	if _, err := newGenerator(t, noKey).Fake("t[x]"); err == nil || !strings.Contains(err.Error(), "no key") {
		t.Fatalf("Fake(t[x]) = %v, want no column to select by", err)
	}
}

func TestTableDescendsToALinkedTable(t *testing.T) {
	f := newGenerator(t, writeFiles(t, geo()), WithSeed(2))
	for i := 0; i < 200; i++ {
		if m := fake(t, f, "region[12].municipality.code"); regionOf[m] != "12" {
			t.Fatalf("region[12].municipality.code = %q, outside 12", m)
		}
		if l := fake(t, f, "region[12].locality.code"); regionOf[municipalityOf[l]] != "12" {
			t.Fatalf("region[12].locality.code = %q, outside 12", l)
		}
		if l := fake(t, f, "municipality[1480].locality"); l != "Göteborg" && l != "Hisingen" {
			t.Fatalf("municipality[1480].locality = %q", l)
		}
		if l := fake(t, f, "region.municipality.locality.name"); l == "" {
			t.Fatal("region.municipality.locality.name rendered empty")
		}
	}
	r, err := f.FakeRecord("region[14].municipality")
	if err != nil {
		t.Fatal(err)
	}
	if line := r.CSVLine(); line != "1480,Göteborg,590000,14" {
		t.Fatalf("record inside region 14 = %q", line)
	}
}

func TestLinkedTablesDrawConsistently(t *testing.T) {
	spellings := map[string]string{
		"leaf first":   `{"format":"{l}|{m}|{r}","l":"{/locality.code}","m":"{/municipality.code}","r":"{/region.code}"}`,
		"root first":   `{"format":"{r}|{m}|{l}","r":"{/region.code}","m":"{/municipality.code}","l":"{/locality.code}"}`,
		"skipping one": `{"format":"{r}|{l}","r":"{/region.code}","l":"{/locality.code}"}`,
		"nested":       `{"format":"{a}|{l}","a":{"format":"{r}|{m}","r":"{/region.code}","m":"{/municipality.code}"},"l":"{/locality.code}"}`,
		"a record":     `{"format":"","l":"{/locality.code}","m":"{/municipality.code}","r":"{/region.code}"}`,
	}
	for name, addr := range spellings {
		f := newGenerator(t, writeFiles(t, with(geo(), map[string]string{"addr.json": addr})), WithSeed(5))
		seen := map[string]bool{}
		for i := 0; i < 300; i++ {
			var parts []string
			if name == "a record" {
				r, err := f.FakeRecord("addr")
				if err != nil {
					t.Fatal(err)
				}
				for _, c := range r.Columns() {
					parts = append(parts, c.Value)
				}
			} else {
				parts = strings.Split(fake(t, f, "addr"), "|")
			}
			var l, m, r string
			for _, p := range parts {
				switch {
				case strings.HasPrefix(p, "L"):
					l = p
				case len(p) == 4:
					m = p
				default:
					r = p
				}
			}
			if m == "" {
				m = municipalityOf[l]
			}
			if municipalityOf[l] != m || regionOf[m] != r {
				t.Fatalf("%s: %v is not one consistent draw", name, parts)
			}
			seen[l] = true
		}
		if len(seen) < 4 {
			t.Fatalf("%s: only %v drawn in 300 renders", name, seen)
		}
	}
}

func TestLinkedTablesDrawApartAcrossGroupsAndRepeats(t *testing.T) {
	files := with(geo(), map[string]string{
		"groups.json": `{"format":"{a}|{b}","a":{"format":"{/locality.code}","drawGroup":"g"},"b":"{/locality.code}"}`,
		"many.json":   `{"format":"{x}","x":{"format":"{/locality.code}","repeat":8,"separator":"|"}}`,
	})
	f := newGenerator(t, writeFiles(t, files), WithSeed(9))
	for _, path := range []string{"groups", "many"} {
		differ := false
		for i := 0; i < 100 && !differ; i++ {
			parts := strings.Split(fake(t, f, path), "|")
			for _, p := range parts[1:] {
				differ = differ || p != parts[0]
			}
		}
		if !differ {
			t.Fatalf("%s: every draw agreed in 100 renders, want groups and repeat iterations drawn apart", path)
		}
	}
}

func TestTableSelectorInAReference(t *testing.T) {
	files := with(geo(), map[string]string{
		"x.json": `{"format":"{a} {b} {c}","a":"{/region[12].name}","b":"{/region[12].municipality.code}","c":"{/region[12].locality.code}"}`,
	})
	f := newGenerator(t, writeFiles(t, files), WithSeed(1))
	for i := 0; i < 100; i++ {
		parts := strings.Fields(fake(t, f, "x"))
		m, l := parts[len(parts)-2], parts[len(parts)-1]
		if !strings.HasPrefix(fake(t, f, "x"), "Skåne län") || regionOf[m] != "12" || municipalityOf[l] != m {
			t.Fatalf("x = %v, want one draw inside region 12", parts)
		}
	}
	for name, c := range map[string]struct{ json, want string }{
		"unknown row":          {`"{/region[99].name}"`, `"99"`},
		"ambiguous name":       {`"{/locality[Sandby].name}"`, "L7 L8"},
		"not inside":           {`"{/region[12].municipality[0180].name}"`, "not inside"},
		"selector on template": {`"{/x[1].a}"`, "not a table"},
	} {
		_, err := New(WithoutShippedData(), WithDataPath(writeFiles(t, with(files, map[string]string{"bad.json": c.json}))))
		if err == nil || !strings.Contains(err.Error(), c.want) {
			t.Errorf("%s: New = %v, want an error mentioning %q", name, err, c.want)
		}
	}
}

func TestTableSelectionFences(t *testing.T) {
	rejected := map[string]struct{ json, want string }{
		"bare beside a path":            {`"{/region} {/region.name}"`, "reads a path into"},
		"bare beside a linked path":     {`"{/region} {/locality.name}"`, "drawGroup"},
		"selected beside unselected":    {`"{/region[12].municipality.name} {/municipality.code}"`, "{/region[12].municipality.code}"},
		"two selections":                {`"{/region[12].name} {/region[14].name}"`, "drawGroup"},
		"selection beside a descendant": {`"{/region[12].name} {/locality.code}"`, "{/region[12].locality.code}"},
	}
	for name, c := range rejected {
		_, err := New(WithoutShippedData(), WithDataPath(writeFiles(t, with(geo(), map[string]string{"x.json": c.json}))))
		if err == nil || !strings.Contains(err.Error(), c.want) {
			t.Errorf("%s: New = %v, want it rejected mentioning %q", name, err, c.want)
		}
	}
	accepted := map[string]string{
		"a descent beside a path into it": `"{/region.municipality} {/region.municipality.name}"`,
		"selections in two groups":        `{"format":"{a} {b}","a":{"format":"{/region[12].name}","drawGroup":"a"},"b":"{/region[14].name}"}`,
		"one selection twice":             `"{/region[12].name} {/region[12].timezone} {/region[12].locality.name}"`,
		"a bare table in another group":   `{"format":"{a} {b}","a":{"format":"{/region}","drawGroup":"a"},"b":"{/locality.name}"}`,
	}
	for name, json := range accepted {
		f, err := New(WithoutShippedData(), WithDataPath(writeFiles(t, with(geo(), map[string]string{"x.json": json}))), WithSeed(1))
		if err != nil {
			t.Errorf("%s: New = %v, want it accepted", name, err)
			continue
		}
		fake(t, f, "x")
	}
	f := newGenerator(t, writeFiles(t, with(geo(), map[string]string{"x.json": accepted["a descent beside a path into it"]})), WithSeed(1))
	for i := 0; i < 100; i++ {
		if parts := strings.Fields(fake(t, f, "x")); parts[0] != parts[1] {
			t.Fatalf("x = %v, want the descended row and the path into it to agree", parts)
		}
	}
}

// The family fence replays each read's selectors through the walk the render uses, so
// spellings that pin the same rows by different routes agree, and two rows of one
// table are refused at load rather than found at render.
func TestTableFamilyFenceReplaysPins(t *testing.T) {
	accepted := map[string]string{
		"skip-level selectors":     `"{/region[12].locality[L4].name}|{/region[12].name}"`,
		"descendant then ancestor": `"{/locality[L4].name}|{/region[12].name}"`,
		"two selected levels":      `"{/municipality[1281].name}|{/locality[L4].name}"`,
		"nested prefixes":          `"{/region[12].municipality[1281].name}|{/municipality[1281].locality[L4].name}"`,
		"selected above a draw":    `"{/region[12].locality[L4].name}|{/region[12].municipality.code}"`,
	}
	for name, json := range accepted {
		f, err := New(WithoutShippedData(), WithDataPath(writeFiles(t, with(geo(), map[string]string{"x.json": json}))), WithSeed(1))
		if err != nil {
			t.Errorf("%s: New = %v, want it accepted", name, err)
			continue
		}
		for i := 0; i < 50; i++ {
			v := fake(t, f, "x")
			if strings.Contains(v, "Sandby") || strings.Contains(v, "Malmö") || strings.Contains(v, "1280") || !strings.Contains(v, "Lund") && !strings.Contains(v, "Skåne") {
				t.Fatalf("%s: x = %q, want every part inside region 12 and Lund", name, v)
			}
		}
	}
	rejected := map[string]struct{ json, want string }{
		"two rows of one table":             {`"{/region[12].locality[L4].name} {/region[12].locality[L7].name}"`, "drawGroup"},
		"a row outside a selected ancestor": {`"{/region[14].name} {/locality[L4].name}"`, "not inside"},
	}
	for name, c := range rejected {
		_, err := New(WithoutShippedData(), WithDataPath(writeFiles(t, with(geo(), map[string]string{"x.json": c.json}))))
		if err == nil || !strings.Contains(err.Error(), c.want) {
			t.Errorf("%s: New = %v, want it rejected mentioning %q", name, err, c.want)
		}
	}
}

func TestTableFences(t *testing.T) {
	base := map[string]string{
		"region.json": `{"format":"{name}","rows":"region.tsv","key":"code","name":"name"}`,
		"region.tsv":  "code\tname\n01\tA\n12\tB\n",
	}
	rejected := map[string]struct {
		files map[string]string
		want  string
	}{
		"rows names a missing file":                    {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv"}`}, "t.tsv"},
		"a TSV nothing names":                          {with(base, map[string]string{"stray.tsv": "a\nx\n"}), "stray.tsv"},
		"rows outside its folder":                      {with(base, map[string]string{"t.json": `{"format":"{code}","rows":"../region.tsv"}`}), "beside"},
		"rows not a tsv":                               {with(base, map[string]string{"t.json": `{"format":"{code}","rows":"region.txt"}`, "region.txt": "code\n1\n"}), ".tsv"},
		"key names no column":                          {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv","key":"b"}`, "t.tsv": "a\nx\ny\n"}, `"b"`},
		"name names no column":                         {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv","name":"b"}`, "t.tsv": "a\nx\ny\n"}, `"b"`},
		"weight names no column":                       {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv","weight":"b"}`, "t.tsv": "a\nx\ny\n"}, `"b"`},
		"parent names no column":                       {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv","parent":"b"}`, "t.tsv": "a\nx\ny\n"}, `"b"`},
		"key equals name":                              {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv","key":"a","name":"a"}`, "t.tsv": "a\nx\ny\n"}, "drop"},
		"duplicate key":                                {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv","key":"a"}`, "t.tsv": "a\nx\nx\n"}, `"x"`},
		"empty key":                                    {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv","key":"a"}`, "t.tsv": "a\tb\n\ty\nx\tz\n"}, "empty"},
		"a bracket in a key":                           {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv","key":"a"}`, "t.tsv": "a\nx[1]\ny\n"}, `"["`},
		"a brace in a name":                            {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv","key":"a","name":"n"}`, "t.tsv": "a\tn\nx\tx{1}\ny\ty\n"}, `"{"`},
		"name without a key":                           {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv","name":"a"}`, "t.tsv": "a\nx\nx\n"}, "key"},
		"a name that is another row's key":             {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv","key":"a","name":"n"}`, "t.tsv": "a\tn\nx\ty\ny\tz\n"}, `"y"`},
		"a cell reading its family":                    {with(geo(), map[string]string{"locality.tsv": "code\tname\tmunicipality\nL1\t{/municipality.code}\t0180\nL2\tSolna\t0184\nL3\tMalmö\t1280\nL4\tLund\t1281\nL5\tGöteborg\t1480\n"}), "family"},
		"a format reading its family":                  {with(geo(), map[string]string{"locality.json": `{"format":"{name} {/region.name}","rows":"locality.tsv","key":"code","name":"name","parent":"municipality"}`}), "family"},
		"a descendant named like an ancestor's column": {with(geo(), map[string]string{"region.tsv": "code\tname\tpopulation\tlocality\n01\tStockholms län\t2400000\tx\n12\tSkåne län\t1400000\ty\n14\tVästra Götalands län\t1750000\tz\n"}), `"locality"`},
		"weight not a number":                          {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv","weight":"w"}`, "t.tsv": "a\tw\nx\tmany\ny\t2\n"}, `"many"`},
		"weight zero":                                  {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv","weight":"w"}`, "t.tsv": "a\tw\nx\t0\ny\t2\n"}, "0"},
		"weight negative":                              {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv","weight":"w"}`, "t.tsv": "a\tw\nx\t-1\ny\t2\n"}, "-1"},
		"reserved column name":                         {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv"}`, "t.tsv": "a\tb.c\nx\ty\n"}, `"b.c"`},
		"duplicate column":                             {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv"}`, "t.tsv": "a\ta\nx\ty\n"}, `"a"`},
		"empty column name":                            {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv"}`, "t.tsv": "a\t\nx\ty\n"}, "empty"},
		"short row":                                    {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv"}`, "t.tsv": "a\tb\nx\ty\nz\n"}, "line 3"},
		"no rows":                                      {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv"}`, "t.tsv": "a\n"}, "no rows"},
		"one row":                                      {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv"}`, "t.tsv": "a\nx\n"}, "one row"},
		"empty file":                                   {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv"}`, "t.tsv": ""}, "header"},
		"parent is not a table":                        {map[string]string{"p.json": `"x"`, "t.json": `{"format":"{a}","rows":"t.tsv","parent":"p"}`, "t.tsv": "a\tp\nx\tx\ny\tx\n"}, "not a table"},
		"parent does not exist":                        {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv","parent":"p"}`, "t.tsv": "a\tp\nx\tx\ny\tx\n"}, `"p"`},
		"parent in another folder":                     {map[string]string{"g/p.json": `{"format":"{k}","rows":"p.tsv","key":"k"}`, "g/p.tsv": "k\nx\ny\n", "t.json": `{"format":"{a}","rows":"t.tsv","parent":"p"}`, "t.tsv": "a\tp\nx\tx\ny\ty\n"}, `"p"`},
		"parent has no key":                            {map[string]string{"p.json": `{"format":"{k}","rows":"p.tsv"}`, "p.tsv": "k\nx\ny\n", "t.json": `{"format":"{a}","rows":"t.tsv","parent":"p"}`, "t.tsv": "a\tp\nx\tx\ny\ty\n"}, "key"},
		"dangling link":                                {with(base, map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv","parent":"region"}`, "t.tsv": "a\tregion\nx\t01\ny\t99\n"}), `"99"`},
		"childless parent row":                         {with(base, map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv","parent":"region"}`, "t.tsv": "a\tregion\nx\t01\ny\t01\n"}), `"12"`},
		"parent cycle":                                 {map[string]string{"a.json": `{"format":"{k}","rows":"a.tsv","key":"k","parent":"b"}`, "a.tsv": "k\tb\nx\tx\ny\ty\n", "b.json": `{"format":"{k}","rows":"b.tsv","key":"k","parent":"a"}`, "b.tsv": "k\ta\nx\tx\ny\ty\n"}, "cycle"},
		"child named like a column":                    {with(base, map[string]string{"name.json": `{"format":"{a}","rows":"name.tsv","parent":"region"}`, "name.tsv": "a\tregion\nx\t01\ny\t12\n"}), `"name"`},
		"rows nested in a field":                       {map[string]string{"t.json": `{"format":"{x}","x":{"format":"{a}","rows":"x.tsv"}}`, "x.tsv": "a\nx\ny\n"}, "category"},
		"rows in a choice item":                        {map[string]string{"t.json": `[{"format":"{a}","rows":"t.tsv"},"y"]`, "t.tsv": "a\nx\ny\n"}, "category"},
		"unknown table option":                         {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv","fields":"a"}`, "t.tsv": "a\nx\ny\n"}, "a table takes"},
		"repeat on a table":                            {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv","repeat":2}`, "t.tsv": "a\nx\ny\n"}, "a table takes"},
		"drawGroup on a table":                         {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv","drawGroup":"g"}`, "t.tsv": "a\nx\ny\n"}, "a table takes"},
		"option not a string":                          {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv","key":1}`, "t.tsv": "a\nx\ny\n"}, "string"},
		"format names no column":                       {map[string]string{"t.json": `{"format":"{b}","rows":"t.tsv"}`, "t.tsv": "a\nx\ny\n"}, `no column "b"`},
		"format reads into a column":                   {map[string]string{"t.json": `{"format":"{a.x}","rows":"t.tsv"}`, "t.tsv": "a\nx\ny\n"}, `"a"`},
		"a reference into a column":                    {with(base, map[string]string{"t.json": `"{/region.name.x}"`}), "column"},
		"a category referencing itself":                {map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv"}`, "t.tsv": "a\n{/t.a}\ny\n"}, "names the category it sits in"},
	}
	for name, c := range rejected {
		_, err := New(WithoutShippedData(), WithDataPath(writeFiles(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)
		}
	}
	if _, err := New(WithoutShippedData(), WithDataFS(os.DirFS(writeFiles(t, base)))); err != nil {
		t.Fatalf("New(WithDataFS) = %v, want a table loaded from any fs.FS", err)
	}
	inline := newGenerator(t, writeFiles(t, base))
	if _, err := inline.NewTemplate(`{"format":"{a}","rows":"t.tsv"}`); err == nil || !strings.Contains(err.Error(), "inline") {
		t.Fatalf("NewTemplate(rows) = %v, want a table refused inline", err)
	}
	bom := newGenerator(t, writeFiles(t, map[string]string{"t.json": `{"format":"{a}","rows":"t.tsv","key":"a"}`, "t.tsv": "\xEF\xBB\xBFa\tb\nx\t1\ny\t2\n"}), WithSeed(1))
	if v := fake(t, bom, "t[x].b"); v != "1" {
		t.Fatalf("t[x].b under a BOM header = %q, want the mark stripped", v)
	}
	empty := newGenerator(t, writeFiles(t, map[string]string{"t.json": `{"format":"","rows":"t.tsv","key":"a"}`, "t.tsv": "a\tb\nx\t1\ny\t2\n"}), WithSeed(1))
	if v := fake(t, empty, "t"); v != "" {
		t.Fatalf("a record-only table renders %q, want \"\"", v)
	}
	if v := fake(t, empty, "t[y].b"); v != "2" {
		t.Fatalf("t[y].b = %q", v)
	}
}

func TestSameShapedChoiceIsATable(t *testing.T) {
	rows := `[{"format":"{name}","name":"Sweden","alpha2":"SE"},{"format":"{name}","name":"Norway","alpha2":"NO"},{"format":"{name}","name":"Denmark","alpha2":"DK"}]`
	_, err := New(WithoutShippedData(), WithDataPath(writeData(t, map[string]string{"country": rows})))
	for _, want := range []string{"country.tsv", `"rows"`, `alpha2\tname`, "3 "} {
		if err == nil || !strings.Contains(err.Error(), want) {
			t.Fatalf("New(same-shaped choice) = %v, want it refused mentioning %q", err, want)
		}
	}
	weighted := `[{"format":"{name}","name":"Sweden","weight":2},{"format":"{name}","name":"Norway"}]`
	if _, err := New(WithoutShippedData(), WithDataPath(writeData(t, map[string]string{"country": weighted}))); err == nil || !strings.Contains(err.Error(), "weight") {
		t.Fatalf("New(weighted same-shaped choice) = %v, want it refused naming a weight column", err)
	}
	accepted := map[string]string{
		"nested":            `{"format":"{c}","c":` + rows + `}`,
		"a choice field":    `[{"format":"{maker} {model}","maker":"BMW","model":["X3","X5"]},{"format":"{maker} {model}","maker":"Ford","model":["Focus","Fiesta"]}]`,
		"different formats": `[{"format":"{a}-{b}","a":"1","b":"2"},{"format":"{b}-{a}","a":"3","b":"4"}]`,
		"different fields":  `[{"format":"{a}","a":"1","b":"2"},{"format":"{a}","a":"3"}]`,
		"a string item":     `[{"format":"{a}","a":"1"},"x"]`,
		"strings":           `["a","b","c"]`,
	}
	for name, json := range accepted {
		if _, err := New(WithoutShippedData(), WithDataPath(writeData(t, map[string]string{"x": json}))); err != nil {
			t.Errorf("%s: New = %v, want it accepted", name, err)
		}
	}
	f := newGenerator(t, writeData(t, map[string]string{"w": `"x"`}))
	if _, err := f.NewTemplate(rows); err != nil {
		t.Fatalf("NewTemplate(same-shaped choice) = %v, want an inline template exempt", err)
	}
}

func TestTableInAStructTag(t *testing.T) {
	f := newGenerator(t, writeFiles(t, geo()), WithSeed(1))
	var v struct {
		Region   string `fake:"region[12].name"`
		Locality string `fake:"region[12].locality.code"`
		Any      string `fake:"{/region[Skåne län].timezone}-x"` // the row region[12] names, by name
	}
	if err := f.FakeStruct(&v); err != nil {
		t.Fatal(err)
	}
	if v.Region != "Skåne län" || regionOf[municipalityOf[v.Locality]] != "12" || v.Any != "Europe/Stockholm-x" {
		t.Fatalf("FakeStruct = %+v, want the selected rows", v)
	}
}

func TestTableOverridesByLayering(t *testing.T) {
	mine := writeFiles(t, map[string]string{
		"misc/country.json": `{"format":"{name}","rows":"country.tsv","key":"alpha2"}`,
		"misc/country.tsv":  "alpha2\tname\nXX\tNowhere\nYY\tElsewhere\n",
	})
	f, err := New(WithDataPath(mine), WithSeed(1))
	if err != nil {
		t.Fatal(err)
	}
	if v := fake(t, f, "misc.country[XX]"); v != "Nowhere" {
		t.Fatalf("misc.country[XX] = %q, want the layered table", v)
	}
	if paths := f.List(); slices.Contains(paths, "misc.country.alpha3") {
		t.Fatal("List() still offers the shipped table's columns under an overridden category")
	}
}

func TestShippedTables(t *testing.T) {
	f := newGenerator(t, "data/misc", WithSeed(1))
	for path, want := range map[string]string{
		"country[SE]":                    "Sweden",
		"country[Sweden].alpha3":         "SWE",
		"country[SE].numeric":            "752",
		"country[SE].tld":                ".se",
		"country[SE].calling-code":       "46",
		"country[SE].capital":            "Stockholm",
		"country[SE].currency":           "SEK",
		"country[SE].flag":               "🇸🇪",
		"currency[SEK].name":             "Swedish Krona",
		"currency[SEK].symbol":           "kr",
		"currency[SEK].numeric":          "752",
		"currency[SEK].decimals":         "2",
		"currency[Euro].code":            "EUR",
		"language[sv]":                   "Swedish",
		"httpstatus[404]":                "404 Not Found",
		"httpstatus[404].reason":         "Not Found",
		"mimetype[application/json].ext": ".json",
	} {
		if got := fake(t, f, path); got != want {
			t.Errorf("Fake(%q) = %q, want %q", path, got, want)
		}
	}
	re := map[string]*regexp.Regexp{
		"country.numeric":      regexp.MustCompile(`^\d{3}$`),
		"country.tld":          regexp.MustCompile(`^\.[a-z]{2}$`),
		"country.calling-code": regexp.MustCompile(`^\d{1,4}(-\d{3})?$`),
		"country.capital":      regexp.MustCompile(`\p{L}`),
		"country.currency":     regexp.MustCompile(`^[A-Z]{3}$`),
		"country.flag":         regexp.MustCompile(`^[\x{1F1E6}-\x{1F1FF}]{2}$`),
		"country.languages":    regexp.MustCompile(`^[a-z]{2,3}(-[A-Z]{2})?(,[a-z]{2,3}(-[A-Z]{2})?)*$`),
		"currency.numeric":     regexp.MustCompile(`^\d{3}$`),
		"currency.decimals":    regexp.MustCompile(`^[0-4]$`),
	}
	for i := 0; i < 100; i++ {
		for p, rx := range re {
			if v := fake(t, f, p); !rx.MatchString(v) {
				t.Fatalf("misc %s = %q, want %s", p, v, rx)
			}
		}
	}
	count := map[string]bool{}
	for i := 0; i < 5000; i++ {
		count[fake(t, f, "country.alpha2")] = true
	}
	if len(count) < 200 {
		t.Fatalf("country draws %d distinct rows in 5000, want the full register", len(count))
	}
}