package service

import (
	"encoding/json"
	"testing"
	"unicode/utf16"
)

// utf16Slice extracts a span the way a JavaScript client would, so the tests
// assert the offsets are usable by the actual renderer rather than merely
// self-consistent.
func utf16Slice(s string, offset, length int) string {
	u := utf16.Encode([]rune(s))
	if offset < 0 || offset+length > len(u) {
		return "<out of range>"
	}
	return string(utf16.Decode(u[offset : offset+length]))
}

func TestParseEntities_Markers(t *testing.T) {
	tests := []struct {
		name     string
		raw      string
		wantBody string
		wantSpan map[string]string // entity type -> the text it should cover
	}{
		{"bold", "hello *world*", "hello world", map[string]string{"bold": "world"}},
		{"strike", "~gone~ now", "gone now", map[string]string{"strike": "gone"}},
		{"code", "run `go test` please", "run go test please", map[string]string{"code": "go test"}},
		{"markers stripped from body", "*a* ~b~ `c`", "a b c", nil},
	}
	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			body, entities := ParseEntities(tc.raw)
			if body != tc.wantBody {
				t.Fatalf("body = %q, want %q", body, tc.wantBody)
			}
			for kind, want := range tc.wantSpan {
				found := false
				for _, e := range entities {
					if e.Type == kind {
						if got := utf16Slice(body, e.Offset, e.Length); got != want {
							t.Errorf("%s covers %q, want %q", kind, got, want)
						}
						found = true
					}
				}
				if !found {
					t.Errorf("no %s entity in %+v", kind, entities)
				}
			}
		})
	}
}

// Offsets are UTF-16 code units because the client slices JS strings with them.
// Devanāgarī is multi-byte and emoji are surrogate pairs, so a byte- or
// rune-based offset would silently mis-highlight in exactly this app's content.
func TestParseEntities_UTF16Offsets(t *testing.T) {
	tests := []struct{ name, raw, want string }{
		{"devanagari prefix", "श्री कृष्ण *bold*", "bold"},
		{"emoji prefix", "🙏🙏 *namaste*", "namaste"},
		{"emoji inside span", "*🙏 namaste*", "🙏 namaste"},
		{"iast prefix", "Bhagavad-gītā ~old~", "old"},
	}
	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			body, entities := ParseEntities(tc.raw)
			if len(entities) == 0 {
				t.Fatalf("no entities for %q (body %q)", tc.raw, body)
			}
			e := entities[len(entities)-1]
			if got := utf16Slice(body, e.Offset, e.Length); got != tc.want {
				t.Errorf("span covers %q, want %q (body %q, entity %+v)", got, tc.want, body, e)
			}
		})
	}
}

// Text that merely contains marker characters must survive untouched.
func TestParseEntities_NotFormatting(t *testing.T) {
	for _, raw := range []string{
		"2*3*4",             // mid-word asterisks
		"a~b~c",             // mid-word tildes
		"* not bold",        // space after opener
		"unmatched *marker", // no closer
		"**",                // empty
		"5 * 3 = 15",        // spaced operators
	} {
		body, entities := ParseEntities(raw)
		if body != raw {
			t.Errorf("ParseEntities(%q) rewrote body to %q", raw, body)
		}
		for _, e := range entities {
			if e.Type != EntityURL {
				t.Errorf("ParseEntities(%q) produced %s entity %+v", raw, e.Type, e)
			}
		}
	}
}

func TestParseEntities_Nesting(t *testing.T) {
	body, entities := ParseEntities("*bold with `code` inside*")
	const wantBody = "bold with code inside"
	if body != wantBody {
		t.Fatalf("body = %q, want %q", body, wantBody)
	}
	var bold, code *Entity
	for i := range entities {
		switch entities[i].Type {
		case EntityBold:
			bold = &entities[i]
		case EntityCode:
			code = &entities[i]
		}
	}
	if bold == nil || code == nil {
		t.Fatalf("want both bold and code, got %+v", entities)
	}
	if got := utf16Slice(body, bold.Offset, bold.Length); got != wantBody {
		t.Errorf("bold covers %q, want the whole body", got)
	}
	if got := utf16Slice(body, code.Offset, code.Length); got != "code" {
		t.Errorf("code covers %q, want %q", got, "code")
	}
	// Outer span must sort first so a renderer opens it before the nested one.
	if entities[0].Type != EntityBold {
		t.Errorf("entities[0] = %s, want the outer bold span first", entities[0].Type)
	}
}

func TestParseEntities_URLs(t *testing.T) {
	tests := []struct {
		name     string
		raw      string
		wantText string
		wantHref string
	}{
		{"https", "see https://prabhupadasays.org/bg/2/13 here",
			"https://prabhupadasays.org/bg/2/13", "https://prabhupadasays.org/bg/2/13"},
		{"bare www gets a scheme", "visit www.prabhupadasays.org now",
			"www.prabhupadasays.org", "https://www.prabhupadasays.org"},
		{"trailing sentence punctuation excluded", "read https://example.org/a.",
			"https://example.org/a", "https://example.org/a"},
	}
	for _, tc := range tests {
		t.Run(tc.name, func(t *testing.T) {
			body, entities := ParseEntities(tc.raw)
			var url *Entity
			for i := range entities {
				if entities[i].Type == EntityURL {
					url = &entities[i]
				}
			}
			if url == nil {
				t.Fatalf("no url entity in %+v", entities)
			}
			if got := utf16Slice(body, url.Offset, url.Length); got != tc.wantText {
				t.Errorf("covers %q, want %q", got, tc.wantText)
			}
			if url.URL != tc.wantHref {
				t.Errorf("href = %q, want %q", url.URL, tc.wantHref)
			}
		})
	}
}

// A URL inside backticks is being shown, not linked.
func TestParseEntities_URLInsideCodeIsNotLinked(t *testing.T) {
	_, entities := ParseEntities("run `curl https://example.org` first")
	for _, e := range entities {
		if e.Type == EntityURL {
			t.Errorf("linked a URL inside a code span: %+v", e)
		}
	}
}

// "Bg 2.13" and "e.g" must not become links — the conservative pattern is what
// keeps scripture references from turning blue.
func TestParseEntities_NoFalsePositiveLinks(t *testing.T) {
	for _, raw := range []string{"Bg 2.13 is the verse", "e.g. this one", "version 1.2.3"} {
		_, entities := ParseEntities(raw)
		for _, e := range entities {
			if e.Type == EntityURL {
				t.Errorf("ParseEntities(%q) linked %+v", raw, e)
			}
		}
	}
}

// entities is stored as jsonb; empty must round-trip as [] rather than null so
// the column default and the parser agree.
func TestParseEntities_JSONShape(t *testing.T) {
	_, entities := ParseEntities("plain text")
	if entities == nil {
		entities = []Entity{}
	}
	b, err := json.Marshal(entities)
	if err != nil {
		t.Fatal(err)
	}
	if string(b) != "[]" {
		t.Errorf("marshalled %s, want []", b)
	}
}