package pgstore

import (
	"fmt"
	"testing"
	"time"
)

// perf_test.go: the measurements a projection change has to be judged by.
//
// Benchmarks rather than tests: `go test` does not run them, so the battery stays fast, and the
// numbers are reproducible on demand — `go test ./internal/pgstore/ -bench LibraryPage -run xxx`.
// The note counter was added to the library row from reasoning alone and cost 96% of the page's
// time on a COLD corpus-sized account; this is what says so before and after. The condition is part
// of the number — on a vacuumed corpus the same change reads as about 80%, and see below for both.
//
// ⚠ THE SAME CHANGE HAS TWO HONEST NUMBERS, and the difference is the state of the corpus — which is
// why every figure about it has to carry its conditions or it reads as a contradiction:
//
//   - COLD corpus, never vacuumed (act 4's own measurement): 636 ms a page against 24 ms. That is
//     the number above, and nothing here reproduces it.
//   - VACUUMED corpus, 40 books x 500 chapters, 1000 notes each: 16.8 ms against 3.4 ms, the join
//     alone 9 ms — about 80%. Those are the NORMATIVE figures and their carrier is migration
//     00022_chapter_note_count.sql, which states them with its conditions. It is also the world THIS
//     benchmark measures: `corpus` ends with `vacuum analyze`.
//
// Both are true, they measure different worlds, and the reason to keep both is that a deployment is
// not vacuumed on the day a user's library grows.

// corpus seeds one account with a library the size of a real one: books whose chapters carry
// resolutions, a fifth of them flagged.
func corpus(t testing.TB, s *Store, books, chapters, units int) string {
	t.Helper()
	ctx := t.Context()
	now := fundedAccount(t, s, t.Context(), "u1", "1000")
	for b := range books {
		id := fmt.Sprintf("bk%03d", b)
		seedBook(t, s, ctx, id, "u1", chapters)
		exec(t, s, ctx, `
			insert into chapters (id, book_id, number, units_total, units_edit_done)
			select $1 || '_' || n, $1, n, $2, $2 from generate_series(1, $3) as n`, id, units, chapters)
		exec(t, s, ctx, `
			insert into unit_resolutions (book_id, chapter, unit, wave, shipped, flagged, at, revision)
			select $1, n, u, 'edit', true, (u % 5 = 0), $2, 1
			  from generate_series(1, $3) as n, generate_series(0, $4) as u`,
			id, now, chapters, units-1)
	}
	exec(t, s, ctx, `vacuum analyze`)
	return "u1"
}

func BenchmarkLibraryPage(b *testing.B) {
	s, ctx := testDB(b)
	user := corpus(b, s, 40, 500, 10)
	start := time.Now()
	for b.Loop() {
		if _, err := s.ListBooks(ctx, user, 100, ""); err != nil {
			b.Fatal(err)
		}
	}
	b.ReportMetric(float64(time.Since(start).Milliseconds())/float64(b.N), "ms/page")
}