package database

import (
	"context"
	"database/sql"
	sqldriver "database/sql/driver"
	"errors"
	"fmt"
	"net/http"
)

var dbCtxKey = &contextKey{"database"}

type contextKey struct {
	name string
}

func Middleware(db *sql.DB) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			ctx := Context(r.Context(), db)
			r = r.WithContext(ctx)
			next.ServeHTTP(w, r)
		})
	}
}

func Context(ctx context.Context, db *sql.DB) context.Context {
	return context.WithValue(ctx, dbCtxKey, db)
}

func ForContext(ctx context.Context) (*sql.Conn, error) {
	raw, ok := ctx.Value(dbCtxKey).(*sql.DB)
	if !ok {
		panic(errors.New("Invalid database context"))
	}
	return raw.Conn(ctx)
}

func DBForContext(ctx context.Context) *sql.DB {
	raw, ok := ctx.Value(dbCtxKey).(*sql.DB)
	if !ok {
		panic(errors.New("Invalid database context"))
	}
	return raw
}

func WithTx(ctx context.Context, opts *sql.TxOptions, fn func(tx *sql.Tx) error) error {
	db := DBForContext(ctx)

	tx, err := db.BeginTx(ctx, opts)
	if err != nil {
		return err
	}
	defer tx.Rollback()

	err = fn(tx)

	var txErr error
	if err != nil {
		txErr = tx.Rollback()
	} else {
		txErr = tx.Commit()
	}

	if errors.Is(err, context.Canceled) && errors.Is(txErr, sqldriver.ErrBadConn) {
		// When a query fails because the context has been canceled, pq will
		// return "driver: bad connection" from tx.Rollback. Do not panic in
		// this case. See https://github.com/lib/pq/issues/1137
		return err
	}
	if txErr != nil && txErr != sql.ErrTxDone {
		if err != nil {
			panic(fmt.Errorf("Transaction error: %v\nClosure error: %v", txErr, err))
		} else {
			panic(txErr)
		}
	}
	return err
}