package lagoon

import (
	"bytes"
	"context"
	"database/sql"
	"errors"
	"log/slog"
	"reflect"
	"strings"
	"sync"
	"testing"

	"gorm.io/gorm"
)

type acItem struct {
	ID   uint   `gorm:"column:id;primaryKey"`
	Name string `gorm:"column:name"`
}

func (acItem) TableName() string { return "lagoon_ac_items" }

type acOther struct {
	ID    uint   `gorm:"column:id;primaryKey"`
	Label string `gorm:"column:label"`
}

func (acOther) TableName() string { return "lagoon_ac_others" }

// recorder collects after-commit callback names and whether the row they
// were registered for was visible to another connection when they ran.
type recorder struct {
	mu  sync.Mutex
	got []string
}

func (r *recorder) add(name string) {
	r.mu.Lock()
	defer r.mu.Unlock()
	r.got = append(r.got, name)
}

func (r *recorder) names() []string {
	r.mu.Lock()
	defer r.mu.Unlock()
	return append([]string(nil), r.got...)
}

func committedCount(t *testing.T, db *sql.DB, name string) int {
	t.Helper()
	var n int
	if err := db.QueryRowContext(context.Background(), `SELECT count(*) FROM lagoon_ac_items WHERE name = $1`, name).Scan(&n); err != nil {
		t.Error(err)
	}
	return n
}

// TestTransactionAfterCommit covers the after-commit seam: callbacks run
// only after a successful commit, in order, and never for rolled-back work.
func TestTransactionAfterCommit(t *testing.T) {
	db, _ := dedicatedDB(t, "lagoon_after_commit")
	gdb, err := Use(t.Context(), db)
	if err != nil {
		t.Fatal(err)
	}
	if err := gdb.Exec(`CREATE TABLE lagoon_ac_items (id SERIAL PRIMARY KEY, name TEXT NOT NULL UNIQUE)`).Error; err != nil {
		t.Fatal(err)
	}
	ctx := t.Context()

	t.Run("commit_runs_in_order", func(t *testing.T) {
		var r recorder
		err := Transaction(ctx, gdb, func(ctx context.Context, tx *gorm.DB) error {
			AfterCommit(ctx, tx, func(context.Context, *gorm.DB) {
				if committedCount(t, db, "ordered") != 1 {
					t.Error("callback ran before the row was committed")
				}
				r.add("a")
			})
			if err := tx.Create(&acItem{Name: "ordered"}).Error; err != nil {
				return err
			}
			AfterCommit(ctx, tx, func(context.Context, *gorm.DB) { r.add("b") })
			if len(r.names()) != 0 {
				t.Error("callback ran inside the transaction")
			}
			return nil
		})
		if err != nil {
			t.Fatal(err)
		}
		if got := r.names(); !reflect.DeepEqual(got, []string{"a", "b"}) {
			t.Fatalf("callbacks = %v, want [a b]", got)
		}
	})

	t.Run("rollback_runs_none", func(t *testing.T) {
		var r recorder
		rollback := errors.New("rollback")
		err := Transaction(ctx, gdb, func(ctx context.Context, tx *gorm.DB) error {
			AfterCommit(ctx, tx, func(context.Context, *gorm.DB) { r.add("x") })
			if err := tx.Create(&acItem{Name: "rolled-back"}).Error; err != nil {
				return err
			}
			return rollback
		})
		if !errors.Is(err, rollback) {
			t.Fatalf("err = %v", err)
		}
		if got := r.names(); len(got) != 0 {
			t.Fatalf("callbacks after rollback = %v", got)
		}
		if committedCount(t, db, "rolled-back") != 0 {
			t.Fatal("row survived the rollback")
		}
	})

	t.Run("nested_failure_drops_inner", func(t *testing.T) {
		var r recorder
		err := Transaction(ctx, gdb, func(ctx context.Context, tx *gorm.DB) error {
			AfterCommit(ctx, tx, func(context.Context, *gorm.DB) { r.add("outer") })
			inner := Transaction(ctx, tx, func(ctx context.Context, tx *gorm.DB) error {
				AfterCommit(ctx, tx, func(context.Context, *gorm.DB) { r.add("inner-failed") })
				if err := tx.Create(&acItem{Name: "inner-failed"}).Error; err != nil {
					return err
				}
				return errors.New("inner fails")
			})
			if inner == nil {
				t.Error("inner transaction did not fail")
			}
			return Transaction(ctx, tx, func(ctx context.Context, tx *gorm.DB) error {
				AfterCommit(ctx, tx, func(context.Context, *gorm.DB) { r.add("inner-ok") })
				return tx.Create(&acItem{Name: "inner-ok"}).Error
			})
		})
		if err != nil {
			t.Fatal(err)
		}
		if got := r.names(); !reflect.DeepEqual(got, []string{"outer", "inner-ok"}) {
			t.Fatalf("callbacks = %v, want [outer inner-ok]", got)
		}
		if committedCount(t, db, "inner-failed") != 0 || committedCount(t, db, "inner-ok") != 1 {
			t.Fatal("savepoint work was not rolled back or kept as expected")
		}
	})

	t.Run("panicking_callback_does_not_fail_commit", func(t *testing.T) {
		var r recorder
		err := Transaction(ctx, gdb, func(ctx context.Context, tx *gorm.DB) error {
			AfterCommit(ctx, tx, func(context.Context, *gorm.DB) { panic("boom") })
			AfterCommit(ctx, tx, func(context.Context, *gorm.DB) { r.add("after-panic") })
			return nil
		})
		if err != nil {
			t.Fatalf("committed transaction reported %v", err)
		}
		if got := r.names(); !reflect.DeepEqual(got, []string{"after-panic"}) {
			t.Fatalf("callbacks = %v", got)
		}
	})

	t.Run("implicit_single_statement", func(t *testing.T) {
		// A separate handle so the test callback stays off the shared one.
		g2, err := Use(ctx, db)
		if err != nil {
			t.Fatal(err)
		}
		var r recorder
		if err := g2.Callback().Create().Before("gorm:create").Register("lagoon_test:after_commit", func(stmt *gorm.DB) {
			item, ok := stmt.Statement.Dest.(*acItem)
			if !ok {
				return
			}
			name := item.Name
			AfterCommit(stmt.Statement.Context, stmt, func(context.Context, *gorm.DB) {
				if committedCount(t, db, name) != 1 {
					t.Errorf("callback for %s ran before commit", name)
				}
				r.add(name)
			})
		}); err != nil {
			t.Fatal(err)
		}
		if err := g2.WithContext(ctx).Create(&acItem{Name: "implicit"}).Error; err != nil {
			t.Fatal(err)
		}
		if err := g2.WithContext(ctx).Create(&acItem{Name: "implicit"}).Error; err == nil {
			t.Fatal("duplicate insert succeeded")
		}
		if got := r.names(); !reflect.DeepEqual(got, []string{"implicit"}) {
			t.Fatalf("callbacks = %v, want only the committed insert", got)
		}
	})

	t.Run("plain_gorm_transaction_is_refused", func(t *testing.T) {
		var logs bytes.Buffer
		previous := slog.Default()
		slog.SetDefault(slog.New(slog.NewTextHandler(&logs, &slog.HandlerOptions{Level: slog.LevelWarn})))
		defer slog.SetDefault(previous)
		ran := false
		err := gdb.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
			AfterCommit(ctx, tx, func(context.Context, *gorm.DB) { ran = true })
			return nil
		})
		if err != nil {
			t.Fatal(err)
		}
		if ran {
			t.Fatal("callback ran inside an unmanaged transaction")
		}
		if !strings.Contains(logs.String(), "after-commit callback skipped inside unmanaged transaction") {
			t.Fatalf("warning = %q", logs.String())
		}
	})

	// The handle a callback receives has an empty statement on the write's
	// connection: a query through it (with WithContext, as application code
	// writes it) must not continue from the written model's statement.
	t.Run("callback_handle_has_a_clean_statement", func(t *testing.T) {
		if err := gdb.Exec(`CREATE TABLE lagoon_ac_others (id SERIAL PRIMARY KEY, label TEXT NOT NULL)`).Error; err != nil {
			t.Fatal(err)
		}
		if err := gdb.Exec(`INSERT INTO lagoon_ac_others (label) VALUES ('other')`).Error; err != nil {
			t.Fatal(err)
		}
		g3, err := Use(ctx, db)
		if err != nil {
			t.Fatal(err)
		}
		var mu sync.Mutex
		labels := map[string]string{}
		if err := g3.Callback().Create().Before("gorm:create").Register("lagoon_test:clean_handle", func(stmt *gorm.DB) {
			item, ok := stmt.Statement.Dest.(*acItem)
			if !ok {
				return
			}
			name := item.Name
			AfterCommit(stmt.Statement.Context, stmt, func(ctx context.Context, d *gorm.DB) {
				var o acOther
				label := ""
				if err := d.WithContext(ctx).Take(&o).Error; err != nil {
					label = "error: " + err.Error()
				} else {
					label = o.Label
				}
				mu.Lock()
				labels[name] = label
				mu.Unlock()
			})
		}); err != nil {
			t.Fatal(err)
		}
		if err := g3.WithContext(ctx).Create(&acItem{Name: "clean-implicit"}).Error; err != nil {
			t.Fatal(err)
		}
		if err := g3.WithContext(ctx).Transaction(func(tx *gorm.DB) error {
			return tx.Create(&acItem{Name: "clean-plain-tx"}).Error
		}); err != nil {
			t.Fatal(err)
		}
		if err := Transaction(ctx, g3, func(ctx context.Context, tx *gorm.DB) error {
			return tx.WithContext(ctx).Create(&acItem{Name: "clean-lagoon-tx"}).Error
		}); err != nil {
			t.Fatal(err)
		}
		mu.Lock()
		defer mu.Unlock()
		for _, name := range []string{"clean-implicit", "clean-lagoon-tx"} {
			if got := labels[name]; got != "other" {
				t.Errorf("%s: query through the callback handle read %q, want the lagoon_ac_others row \"other\"", name, got)
			}
		}
		if _, ok := labels["clean-plain-tx"]; ok {
			t.Fatal("unmanaged transaction callback ran")
		}
	})

	t.Run("outside_transaction_runs_now", func(t *testing.T) {
		ran := false
		AfterCommit(ctx, gdb, func(context.Context, *gorm.DB) { ran = true })
		if !ran {
			t.Fatal("callback outside a transaction did not run immediately")
		}
	})
}

// TestTransactionEdges covers the argument edges of Transaction and
// AfterCommit.
func TestTransactionEdges(t *testing.T) {
	if err := Transaction(context.Background(), nil, func(context.Context, *gorm.DB) error { return nil }); err == nil {
		t.Fatal("Transaction accepted a nil handle")
	}
	AfterCommit(context.Background(), nil, nil) // a nil fn is a no-op
	ran := false
	AfterCommit(nil, nil, func(ctx context.Context, db *gorm.DB) {
		if ctx == nil || db != nil {
			t.Error("nil ctx and handle were not normalized")
		}
		ran = true
	})
	if !ran {
		t.Fatal("AfterCommit without a handle did not run immediately")
	}
	if cleanHandle(nil, context.Background()) != nil {
		t.Fatal("cleanHandle(nil) is not nil")
	}
	db, _ := dedicatedDB(t, "lagoon_after_commit_edges")
	gdb, err := Use(t.Context(), db)
	if err != nil {
		t.Fatal(err)
	}
	var got context.Context
	if err := Transaction(nil, gdb, func(ctx context.Context, tx *gorm.DB) error {
		AfterCommit(ctx, tx, func(ctx context.Context, _ *gorm.DB) { got = ctx })
		return nil
	}); err != nil {
		t.Fatal(err)
	}
	if got == nil {
		t.Fatal("callback of a Transaction with a nil ctx did not run with a context")
	}
	var nestedRan bool
	var nestedEntered bool
	err = Transaction(t.Context(), gdb, func(ctx context.Context, _ *gorm.DB) error {
		return Transaction(ctx, gdb, func(ctx context.Context, tx *gorm.DB) error {
			nestedEntered = true
			AfterCommit(ctx, tx, func(context.Context, *gorm.DB) { nestedRan = true })
			return nil
		})
	})
	if err == nil || !strings.Contains(err.Error(), "parent transaction handle") {
		t.Fatalf("nested Transaction with root handle err = %v", err)
	}
	if nestedEntered || nestedRan {
		t.Fatal("nested root handle entered work or ran callbacks")
	}
	if err := registerAfterCommit(gdb); err != nil {
		t.Fatalf("registering the after-commit callback twice: %v", err)
	}
}