// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package sql

import (
	"context"
	"database/sql/driver"
	"errors"
)

func ctxDriverPrepare(ctx context.Context, ci driver.Conn, query string) (driver.Stmt, error) {
	if ciCtx, is := ci.(driver.ConnPrepareContext); is {
		return ciCtx.PrepareContext(ctx, query)
	}
	si, err := ci.Prepare(query)
	if err == nil {
		select {
		default:
		case <-ctx.Done():
			si.Close()
			return nil, ctx.Err()
		}
	}
	return si, err
}

func ctxDriverExec(ctx context.Context, execer driver.Execer, query string, nvdargs []driver.NamedValue) (driver.Result, error) {
	if execerCtx, is := execer.(driver.ExecerContext); is {
		return execerCtx.ExecContext(ctx, query, nvdargs)
	}
	dargs, err := namedValueToValue(nvdargs)
	if err != nil {
		return nil, err
	}

	resi, err := execer.Exec(query, dargs)
	if err == nil {
		select {
		default:
		case <-ctx.Done():
			return resi, ctx.Err()
		}
	}
	return resi, err
}

func ctxDriverQuery(ctx context.Context, queryer driver.Queryer, query string, nvdargs []driver.NamedValue) (driver.Rows, error) {
	if queryerCtx, is := queryer.(driver.QueryerContext); is {
		ret, err := queryerCtx.QueryContext(ctx, query, nvdargs)
		return ret, err
	}
	dargs, err := namedValueToValue(nvdargs)
	if err != nil {
		return nil, err
	}

	rowsi, err := queryer.Query(query, dargs)
	if err == nil {
		select {
		default:
		case <-ctx.Done():
			rowsi.Close()
			return nil, ctx.Err()
		}
	}
	return rowsi, err
}

func ctxDriverStmtExec(ctx context.Context, si driver.Stmt, nvdargs []driver.NamedValue) (driver.Result, error) {
	if siCtx, is := si.(driver.StmtExecContext); is {
		return siCtx.ExecContext(ctx, nvdargs)
	}
	dargs, err := namedValueToValue(nvdargs)
	if err != nil {
		return nil, err
	}

	resi, err := si.Exec(dargs)
	if err == nil {
		select {
		default:
		case <-ctx.Done():
			return resi, ctx.Err()
		}
	}
	return resi, err
}

func ctxDriverStmtQuery(ctx context.Context, si driver.Stmt, nvdargs []driver.NamedValue) (driver.Rows, error) {
	if siCtx, is := si.(driver.StmtQueryContext); is {
		return siCtx.QueryContext(ctx, nvdargs)
	}
	dargs, err := namedValueToValue(nvdargs)
	if err != nil {
		return nil, err
	}

	rowsi, err := si.Query(dargs)
	if err == nil {
		select {
		default:
		case <-ctx.Done():
			rowsi.Close()
			return nil, ctx.Err()
		}
	}
	return rowsi, err
}

var errLevelNotSupported = errors.New("sql: selected isolation level is not supported")

func ctxDriverBegin(ctx context.Context, ci driver.Conn) (driver.Tx, error) {
	if ciCtx, is := ci.(driver.ConnBeginContext); is {
		return ciCtx.BeginContext(ctx)
	}

	if ctx.Done() == context.Background().Done() {
		return ci.Begin()
	}

	// Check the transaction level in ctx. If set and non-default
	// then return an error here as the BeginContext driver value is not supported.
	if level, ok := driver.IsolationFromContext(ctx); ok && level != driver.IsolationLevel(LevelDefault) {
		return nil, errors.New("sql: driver does not support non-default isolation level")
	}

	// Check for a read-only parameter in ctx. If a read-only transaction is
	// requested return an error as the BeginContext driver value is not supported.
	if ro := driver.ReadOnlyFromContext(ctx); ro {
		return nil, errors.New("sql: driver does not support read-only transactions")
	}

	txi, err := ci.Begin()
	if err == nil {
		select {
		default:
		case <-ctx.Done():
			txi.Rollback()
			return nil, ctx.Err()
		}
	}
	return txi, err
}

func namedValueToValue(named []driver.NamedValue) ([]driver.Value, error) {
	dargs := make([]driver.Value, len(named))
	for n, param := range named {
		if len(param.Name) > 0 {
			return nil, errors.New("sql: driver does not support the use of Named Parameters")
		}
		dargs[n] = param.Value
	}
	return dargs, nil
}