package services

import (
	"testing"

	"github.com/google/uuid"
	"github.com/jackc/pgx/v5/pgtype"
)

func mustUUID(t *testing.T, raw string) pgtype.UUID {
	t.Helper()
	parsed, err := uuid.Parse(raw)
	if err != nil {
		t.Fatalf("invalid test uuid %q: %v", raw, err)
	}
	return pgtype.UUID{Bytes: parsed, Valid: true}
}

// alwaysExists simulates every candidate's file still being on disk:
// deliberate copies across libraries must never be repointed.
func TestSelectMoveCandidateAllFilesExist(t *testing.T) {
	candidates := []moveCandidate{
		{ID: mustUUID(t, "00000000-0000-0000-0000-000000000001"), FilePath: "a/book.epub"},
		{ID: mustUUID(t, "00000000-0000-0000-0000-000000000002"), FilePath: "b/book.epub"},
	}

	if _, ok := selectMoveCandidate(candidates, func(moveCandidate) bool { return true }); ok {
		t.Fatal("expected no move candidate when every file still exists")
	}
}

// Input arrives pre-ordered (archived first, then most missing scans, then
// oldest), so the first missing candidate must win.
func TestSelectMoveCandidatePicksFirstMissing(t *testing.T) {
	onDisk := moveCandidate{ID: mustUUID(t, "00000000-0000-0000-0000-000000000001"), FilePath: "a/book.epub"}
	gone := moveCandidate{ID: mustUUID(t, "00000000-0000-0000-0000-000000000002"), FilePath: "b/book.epub"}
	candidates := []moveCandidate{onDisk, gone}

	got, ok := selectMoveCandidate(candidates, func(c moveCandidate) bool {
		return c.ID == onDisk.ID
	})
	if !ok {
		t.Fatal("expected a move candidate")
	}
	if got.ID != gone.ID {
		t.Fatalf("expected candidate %v, got %v", gone.ID, got.ID)
	}
}

func TestSelectMoveCandidateOnlyMissingQualifies(t *testing.T) {
	gone := moveCandidate{ID: mustUUID(t, "00000000-0000-0000-0000-000000000001"), FilePath: "old/book.epub"}
	candidates := []moveCandidate{gone}

	got, ok := selectMoveCandidate(candidates, func(moveCandidate) bool { return false })
	if !ok {
		t.Fatal("expected the missing candidate to qualify")
	}
	if got.ID != gone.ID {
		t.Fatalf("expected candidate %v, got %v", gone.ID, got.ID)
	}
}

func TestSelectMoveCandidateEmptyList(t *testing.T) {
	if _, ok := selectMoveCandidate(nil, func(moveCandidate) bool { return false }); ok {
		t.Fatal("expected no candidate for an empty list")
	}
}