package fakes

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

// --- format string edge cases ---

func TestEscapeEdgeCases(t *testing.T) {
	f := engine(1)
	cases := map[string]string{
		`{"format":""}`:         "",     // empty format
		`{"format":"#"}`:        "#",    // trailing escape is a literal #
		`{"format":"##"}`:       "#",    // escaped hash
		`{"format":"#0#1#A#a"}`: "01Aa", // escaped class chars stay literal
		`{"format":"#{x#}"}`:    "{x}",  // escaping braces disables tokens
		`{"format":"x}y"}`:      "x}y",  // an unmatched } is literal (x, y aren't classes)
	}
	for tmpl, want := range cases {
		if got := mustRender(t, f, tmpl); got != want {
			t.Errorf("render(%s) = %q, want %q", tmpl, got, want)
		}
	}
}

func TestMultibyteFormat(t *testing.T) {
	// Scanning is rune-aware: multibyte literals coexist with class chars and
	// tokens without corrupting indices.
	got := mustRender(t, engine(2), `{"format":"Öster{x}-0å","x":["väg"]}`)
	if !regexp.MustCompile(`^Österväg-[0-9]å$`).MatchString(got) {
		t.Fatalf("multibyte format = %q", got)
	}
}

func TestAlternationThreeWay(t *testing.T) {
	f := engine(4)
	seen := map[string]bool{}
	for i := 0; i < 200; i++ {
		seen[mustRender(t, f, `{"format":"{a|b|c}","a":["A"],"b":["B"],"c":["C"]}`)] = true
	}
	if !seen["A"] || !seen["B"] || !seen["C"] || len(seen) != 3 {
		t.Fatalf("3-way alternation produced %v, want A, B and C", seen)
	}
}

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([]string{file}); err == nil {
		t.Error("New(file) = nil error, want not-a-directory error")
	}
	// Invalid JSON in a category file fails.
	if _, err := New([]string{writeData(t, map[string]string{"broken": `{ not json`})}); err == nil {
		t.Error("New(invalid JSON) = nil error")
	}
}

// --- deep path navigation ---

func TestDeepDottedPath(t *testing.T) {
	// A 5-segment path descends through alternating object/array nodes; choices
	// on the path are single-variant, so it resolves deterministically.
	f := engine(1)
	f.categories = map[string]node{
		"deep": compiled(t, `[{"format":"{a}","a":[{"format":"{b}","b":[{"format":"{c}","c":[{"format":"{d}","d":["leaf"]}]}]}]}]`),
	}
	if got, err := f.Fake("deep.a.b.c.d"); err != nil || got != "leaf" {
		t.Fatalf("Fake(deep.a.b.c.d) = %q, %v, want leaf", got, err)
	}
	// Rendering the whole tree resolves the same chain.
	if got, err := f.Fake("deep"); err != nil || got != "leaf" {
		t.Fatalf("Fake(deep) = %q, %v, want leaf", got, err)
	}
}

func TestDescendIntoLiteralErrors(t *testing.T) {
	f := engine(1)
	f.categories = map[string]node{"greeting": compiled(t, `["hej"]`)}
	if _, err := f.Fake("greeting.extra"); err == nil {
		t.Fatal("Fake(greeting.extra) = nil error, want descend-into-literal error")
	}
}

// --- category root shapes ---

func TestCategoryRootShapes(t *testing.T) {
	dir := writeData(t, map[string]string{
		"obj": `{"format":"00"}`, // object root
		"lit": `"hello"`,         // bare-string root
	})
	f := newFakes(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)
	}
}

// --- very long lists ---

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 := newFakes(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)
	}
}

// --- composition against the shipped sv_SE data ---

// swedishName matches one or more letter-words, optionally space/hyphen joined
// ("Storgatan", "Norra Promenaden", "von Flemming"). Used by the composition
// tests so shipped name lists can grow without re-enumerating them here.
var swedishName = regexp.MustCompile(`^\p{L}+([ -]\p{L}+)*$`)

func TestShippedStreetComposition(t *testing.T) {
	// street is a choice of composed {first}{last} templates and literal names.
	f := newFakes(t, "data/sv_SE", WithSeed(5))
	for i := 0; i < 300; i++ {
		if s := fake(t, f, "address.street"); !swedishName.MatchString(s) {
			t.Fatalf("street %q is not a Swedish street name", s)
		}
	}
}

func TestShippedLastNameComposition(t *testing.T) {
	// last is a choice of patronymic {first}sson templates and literal surnames.
	f := newFakes(t, "data/sv_SE", WithSeed(6))
	for i := 0; i < 300; i++ {
		if s := fake(t, f, "person.last"); !swedishName.MatchString(s) {
			t.Fatalf("last name %q is not a Swedish surname", s)
		}
	}
}

func TestShippedStreetNumberFormats(t *testing.T) {
	// Reachable via a hyphenated path; covers all five weighted number variants.
	f := newFakes(t, "data/sv_SE", WithSeed(8))
	re := regexp.MustCompile(`^[1-9]\d{0,2}[A-Z]?$`)
	for i := 0; i < 300; i++ {
		if n := fake(t, f, "address.street-number"); !re.MatchString(n) {
			t.Fatalf("street-number %q does not match %s", n, re)
		}
	}
}