// Copyright 2015 PingCAP, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.

package expression

import (
	"regexp"

	"github.com/juju/errors"
	"github.com/pingcap/tidb/context"
	"github.com/pingcap/tidb/util/stringutil"
	"github.com/pingcap/tidb/util/types"
	"github.com/pingcap/tipb/go-tipb"
)

var (
	_ functionClass = &likeFunctionClass{}
	_ functionClass = &regexpFunctionClass{}
)

var (
	_ builtinFunc = &builtinLikeSig{}
	_ builtinFunc = &builtinRegexpBinarySig{}
	_ builtinFunc = &builtinRegexpSig{}
)

type likeFunctionClass struct {
	baseFunctionClass
}

func (c *likeFunctionClass) getFunction(ctx context.Context, args []Expression) (builtinFunc, error) {
	if err := c.verifyArgs(args); err != nil {
		return nil, errors.Trace(err)
	}
	argTp := []types.EvalType{types.ETString, types.ETString, types.ETInt}
	bf := newBaseBuiltinFuncWithTp(ctx, args, types.ETInt, argTp...)
	bf.tp.Flen = 1
	sig := &builtinLikeSig{bf}
	sig.setPbCode(tipb.ScalarFuncSig_LikeSig)
	return sig, nil
}

type builtinLikeSig struct {
	baseBuiltinFunc
}

// evalInt evals a builtinLikeSig.
// See https://dev.mysql.com/doc/refman/5.7/en/string-comparison-functions.html#operator_like
// NOTE: Currently tikv's like function is case sensitive, so we keep its behavior here.
func (b *builtinLikeSig) evalInt(row []types.Datum) (int64, bool, error) {
	sc := b.ctx.GetSessionVars().StmtCtx
	valStr, isNull, err := b.args[0].EvalString(row, sc)
	if isNull || err != nil {
		return 0, isNull, errors.Trace(err)
	}

	// TODO: We don't need to compile pattern if it has been compiled or it is static.
	patternStr, isNull, err := b.args[1].EvalString(row, sc)
	if isNull || err != nil {
		return 0, isNull, errors.Trace(err)
	}
	val, isNull, err := b.args[2].EvalInt(row, sc)
	if isNull || err != nil {
		return 0, isNull, errors.Trace(err)
	}
	escape := byte(val)
	patChars, patTypes := stringutil.CompilePattern(patternStr, escape)
	match := stringutil.DoMatch(valStr, patChars, patTypes)
	return boolToInt64(match), false, nil
}

type regexpFunctionClass struct {
	baseFunctionClass
}

func (c *regexpFunctionClass) getFunction(ctx context.Context, args []Expression) (builtinFunc, error) {
	if err := c.verifyArgs(args); err != nil {
		return nil, errors.Trace(err)
	}
	bf := newBaseBuiltinFuncWithTp(ctx, args, types.ETInt, types.ETString, types.ETString)
	bf.tp.Flen = 1
	var sig builtinFunc
	if types.IsBinaryStr(args[0].GetType()) {
		sig = &builtinRegexpBinarySig{bf}
	} else {
		sig = &builtinRegexpSig{bf}
	}
	return sig, nil
}

type builtinRegexpBinarySig struct {
	baseBuiltinFunc
}

func (b *builtinRegexpBinarySig) evalInt(row []types.Datum) (int64, bool, error) {
	sc := b.ctx.GetSessionVars().StmtCtx

	expr, isNull, err := b.args[0].EvalString(row, sc)
	if isNull || err != nil {
		return 0, true, errors.Trace(err)
	}

	pat, isNull, err := b.args[1].EvalString(row, sc)
	if isNull || err != nil {
		return 0, true, errors.Trace(err)
	}

	// TODO: We don't need to compile pattern if it has been compiled or it is static.
	re, err := regexp.Compile(pat)
	if err != nil {
		return 0, true, errors.Trace(err)
	}
	return boolToInt64(re.MatchString(expr)), false, nil
}

type builtinRegexpSig struct {
	baseBuiltinFunc
}

// evalInt evals `expr REGEXP pat`, or `expr RLIKE pat`.
// See https://dev.mysql.com/doc/refman/5.7/en/regexp.html#operator_regexp
func (b *builtinRegexpSig) evalInt(row []types.Datum) (int64, bool, error) {
	sc := b.ctx.GetSessionVars().StmtCtx

	expr, isNull, err := b.args[0].EvalString(row, sc)
	if isNull || err != nil {
		return 0, true, errors.Trace(err)
	}

	pat, isNull, err := b.args[1].EvalString(row, sc)
	if isNull || err != nil {
		return 0, true, errors.Trace(err)
	}

	// TODO: We don't need to compile pattern if it has been compiled or it is static.
	re, err := regexp.Compile("(?i)" + pat)
	if err != nil {
		return 0, true, errors.Trace(err)
	}
	return boolToInt64(re.MatchString(expr)), false, nil
}