package pipeline

import (
	"reflect"
	"strings"
	"testing"
)

func TestSplitChunksSingleParagraph(t *testing.T) {
	got := SplitChunks("静かな図書館の朝。")
	want := []Chunk{{Chapter: 1, ChunkIdx: 0, Text: "静かな図書館の朝。"}}
	if !reflect.DeepEqual(got, want) {
		t.Fatalf("single paragraph = %+v, want %+v", got, want)
	}
}

func TestSplitChunksChapters(t *testing.T) {
	src := "Глава один." + chapterSep + "Глава два." + chapterSep + "Глава три."
	got := SplitChunks(src)
	want := []Chunk{
		{Chapter: 1, ChunkIdx: 0, Text: "Глава один."},
		{Chapter: 2, ChunkIdx: 0, Text: "Глава два."},
		{Chapter: 3, ChunkIdx: 0, Text: "Глава три."},
	}
	if !reflect.DeepEqual(got, want) {
		t.Fatalf("chapters = %+v, want %+v", got, want)
	}
}

func TestSplitChunksPacksToTarget(t *testing.T) {
	// Two paragraphs that together exceed the target must split into two chunks,
	// each never splitting a paragraph.
	p1 := strings.Repeat("a", 800)
	p2 := strings.Repeat("b", 800)
	got := SplitChunks(p1 + "\n\n" + p2)
	want := []Chunk{
		{Chapter: 1, ChunkIdx: 0, Text: p1},
		{Chapter: 1, ChunkIdx: 1, Text: p2},
	}
	if !reflect.DeepEqual(got, want) {
		t.Fatalf("packing = chapters/chunks %d, want 2 chunks; got %+v", len(got), summarize(got))
	}
}

func TestSplitChunksPacksSmallParagraphsTogether(t *testing.T) {
	// Small paragraphs pack into one chunk (under the target), joined by a blank line.
	got := SplitChunks("Абзац один.\n\nАбзац два.\n\nАбзац три.")
	if len(got) != 1 {
		t.Fatalf("small paragraphs must pack into one chunk, got %d: %+v", len(got), summarize(got))
	}
	if got[0].Text != "Абзац один.\n\nАбзац два.\n\nАбзац три." {
		t.Fatalf("packed text = %q", got[0].Text)
	}
}

func TestSplitChunksOversizeParagraphIsOwnChunk(t *testing.T) {
	big := strings.Repeat("ы", 2000) // > targetChunkChars but never split
	got := SplitChunks(big)
	if len(got) != 1 || got[0].Text != big {
		t.Fatalf("an oversize paragraph must be one un-split chunk, got %+v", summarize(got))
	}
}

func TestSplitChunksDropsEmpties(t *testing.T) {
	// Empty chapter blocks and whitespace-only paragraphs vanish; chapter numbers
	// only advance for non-empty chapters.
	src := "A" + chapterSep + "   \n\n  " + chapterSep + "B"
	got := SplitChunks(src)
	want := []Chunk{
		{Chapter: 1, ChunkIdx: 0, Text: "A"},
		{Chapter: 2, ChunkIdx: 0, Text: "B"},
	}
	if !reflect.DeepEqual(got, want) {
		t.Fatalf("empties = %+v, want %+v", got, want)
	}
}

func TestSplitChunksDeterministic(t *testing.T) {
	src := "Абзац.\n\nЕщё абзац." + chapterSep + strings.Repeat("длинный ", 300)
	a, b := SplitChunks(src), SplitChunks(src)
	if !reflect.DeepEqual(a, b) {
		t.Fatal("SplitChunks must be deterministic")
	}
}

func summarize(cs []Chunk) []string {
	out := make([]string, len(cs))
	for i, c := range cs {
		txt := c.Text
		if len(txt) > 12 {
			txt = txt[:12] + "…"
		}
		out[i] = strings.TrimSpace(txt)
	}
	return out
}