/*
Copyright 2021 Gravitational, 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,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package utils

import (
	"time"

	"github.com/gravitational/trace"

	"github.com/gravitational/teleport/api/types"
	"github.com/gravitational/teleport/api/utils"
)

// Fields represents a generic string-keyed map.
type Fields map[string]interface{}

// GetString returns a string representation of a field.
func (f Fields) GetString(key string) string {
	val, found := f[key]
	if !found {
		return ""
	}
	return val.(string)
}

// GetStrings returns a slice-of-strings representation of a field.
func (f Fields) GetStrings(key string) []string {
	val, found := f[key]
	if !found {
		return nil
	}
	strings, ok := val.([]string)
	if ok {
		return strings
	}
	slice, _ := val.([]interface{})
	res := make([]string, 0, len(slice))
	for _, v := range slice {
		s, ok := v.(string)
		if ok {
			res = append(res, s)
		}
	}
	return res
}

// GetInt returns an int representation of a field.
func (f Fields) GetInt(key string) int {
	val, found := f[key]
	if !found {
		return 0
	}
	v, ok := val.(int)
	if !ok {
		f, ok := val.(float64)
		if ok {
			v = int(f)
		}
	}
	return v
}

// GetTime returns a time.Time representation of a field.
func (f Fields) GetTime(key string) time.Time {
	val, found := f[key]
	if !found {
		return time.Time{}
	}
	v, ok := val.(time.Time)
	if !ok {
		s := f.GetString(key)
		v, _ = time.Parse(time.RFC3339, s)
	}
	return v
}

// HasField returns true if the field exists.
func (f Fields) HasField(key string) bool {
	_, ok := f[key]
	return ok
}

// FieldsCondition is a boolean function on Fields.
type FieldsCondition func(Fields) bool

// ToFieldsCondition converts a WhereExpr into a FieldsCondition.
func ToFieldsCondition(expr *types.WhereExpr) (FieldsCondition, error) {
	if expr == nil {
		return nil, trace.BadParameter("expr is nil")
	}

	binOp := func(e types.WhereExpr2, op func(a, b bool) bool) (FieldsCondition, error) {
		left, err := ToFieldsCondition(e.L)
		if err != nil {
			return nil, trace.Wrap(err)
		}
		right, err := ToFieldsCondition(e.R)
		if err != nil {
			return nil, trace.Wrap(err)
		}
		return func(f Fields) bool { return op(left(f), right(f)) }, nil
	}
	if expr, err := binOp(expr.And, func(a, b bool) bool { return a && b }); err == nil {
		return expr, nil
	}
	if expr, err := binOp(expr.Or, func(a, b bool) bool { return a || b }); err == nil {
		return expr, nil
	}
	if inner, err := ToFieldsCondition(expr.Not); err == nil {
		return func(f Fields) bool { return !inner(f) }, nil
	}

	if expr.Equals.L != nil && expr.Equals.R != nil {
		left, right := expr.Equals.L, expr.Equals.R
		switch {
		case left.Field != "" && right.Field != "":
			return func(f Fields) bool { return f[left.Field] == f[right.Field] }, nil
		case left.Literal != nil && right.Field != "":
			return func(f Fields) bool { return left.Literal == f[right.Field] }, nil
		case left.Field != "" && right.Literal != nil:
			return func(f Fields) bool { return f[left.Field] == right.Literal }, nil
		}
	}
	if expr.Contains.L != nil && expr.Contains.R != nil {
		left, right := expr.Contains.L, expr.Contains.R
		switch {
		case left.Field != "" && right.Field != "":
			return func(f Fields) bool { return utils.SliceContainsStr(f.GetStrings(left.Field), f.GetString(right.Field)) }, nil
		case left.Literal != nil && right.Field != "":
			if ss, ok := left.Literal.([]string); ok {
				return func(f Fields) bool { return utils.SliceContainsStr(ss, f.GetString(right.Field)) }, nil
			}
		case left.Field != "" && right.Literal != nil:
			if s, ok := right.Literal.(string); ok {
				return func(f Fields) bool { return utils.SliceContainsStr(f.GetStrings(left.Field), s) }, nil
			}
		}
	}

	return nil, trace.BadParameter("failed to convert expression %q to FieldsCondition", expr)
}