// Copyright 2024 Kelvin Clement Mwinuka
//
// 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 str

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"github.com/echovault/echovault/internal"
	"github.com/echovault/echovault/internal/config"
	"github.com/echovault/echovault/pkg/constants"
	"github.com/echovault/echovault/pkg/echovault"
	str "github.com/echovault/echovault/pkg/modules/string"
	"github.com/echovault/echovault/pkg/types"
	"github.com/tidwall/resp"
	"net"
	"strconv"
	"strings"
	"testing"
)

var mockServer *echovault.EchoVault

func init() {
	mockServer, _ = echovault.NewEchoVault(
		echovault.WithCommands(str.Commands()),
		echovault.WithConfig(config.Config{
			DataDir:        "",
			EvictionPolicy: constants.NoEviction,
		}),
	)
}

func getHandler(commands ...string) types.HandlerFunc {
	if len(commands) == 0 {
		return nil
	}
	for _, c := range mockServer.GetAllCommands() {
		if strings.EqualFold(commands[0], c.Command) && len(commands) == 1 {
			// Get command handler
			return c.HandlerFunc
		}
		if strings.EqualFold(commands[0], c.Command) {
			// Get sub-command handler
			for _, sc := range c.SubCommands {
				if strings.EqualFold(commands[1], sc.Command) {
					return sc.HandlerFunc
				}
			}
		}
	}
	return nil
}

func getHandlerFuncParams(ctx context.Context, cmd []string, conn *net.Conn) types.HandlerFuncParams {
	return types.HandlerFuncParams{
		Context:          ctx,
		Command:          cmd,
		Connection:       conn,
		KeyExists:        mockServer.KeyExists,
		CreateKeyAndLock: mockServer.CreateKeyAndLock,
		KeyLock:          mockServer.KeyLock,
		KeyRLock:         mockServer.KeyRLock,
		KeyUnlock:        mockServer.KeyUnlock,
		KeyRUnlock:       mockServer.KeyRUnlock,
		GetValue:         mockServer.GetValue,
		SetValue:         mockServer.SetValue,
	}
}

func Test_HandleSetRange(t *testing.T) {
	tests := []struct {
		name             string
		preset           bool
		key              string
		presetValue      string
		command          []string
		expectedValue    string
		expectedResponse int
		expectedError    error
	}{
		{
			name:             "Test that SETRANGE on non-existent string creates new string",
			preset:           false,
			key:              "SetRangeKey1",
			presetValue:      "",
			command:          []string{"SETRANGE", "SetRangeKey1", "10", "New String Value"},
			expectedValue:    "New String Value",
			expectedResponse: len("New String Value"),
			expectedError:    nil,
		},
		{
			name:             "Test SETRANGE with an offset that leads to a longer resulting string",
			preset:           true,
			key:              "SetRangeKey2",
			presetValue:      "Original String Value",
			command:          []string{"SETRANGE", "SetRangeKey2", "16", "Portion Replaced With This New String"},
			expectedValue:    "Original String Portion Replaced With This New String",
			expectedResponse: len("Original String Portion Replaced With This New String"),
			expectedError:    nil,
		},
		{
			name:             "SETRANGE with negative offset prepends the string",
			preset:           true,
			key:              "SetRangeKey3",
			presetValue:      "This is a preset value",
			command:          []string{"SETRANGE", "SetRangeKey3", "-10", "Prepended "},
			expectedValue:    "Prepended This is a preset value",
			expectedResponse: len("Prepended This is a preset value"),
			expectedError:    nil,
		},
		{
			name:             "SETRANGE with offset that embeds new string inside the old string",
			preset:           true,
			key:              "SetRangeKey4",
			presetValue:      "This is a preset value",
			command:          []string{"SETRANGE", "SetRangeKey4", "0", "That"},
			expectedValue:    "That is a preset value",
			expectedResponse: len("That is a preset value"),
			expectedError:    nil,
		},
		{
			name:             "SETRANGE with offset longer than original lengths appends the string",
			preset:           true,
			key:              "SetRangeKey5",
			presetValue:      "This is a preset value",
			command:          []string{"SETRANGE", "SetRangeKey5", "100", " Appended"},
			expectedValue:    "This is a preset value Appended",
			expectedResponse: len("This is a preset value Appended"),
			expectedError:    nil,
		},
		{
			name:             "SETRANGE with offset on the last character replaces last character with new string",
			preset:           true,
			key:              "SetRangeKey6",
			presetValue:      "This is a preset value",
			command:          []string{"SETRANGE", "SetRangeKey6", strconv.Itoa(len("This is a preset value") - 1), " replaced"},
			expectedValue:    "This is a preset valu replaced",
			expectedResponse: len("This is a preset valu replaced"),
			expectedError:    nil,
		},
		{
			name:             " Offset not integer",
			preset:           false,
			command:          []string{"SETRANGE", "key", "offset", "value"},
			expectedResponse: 0,
			expectedError:    errors.New("offset must be an integer"),
		},
		{
			name:             "SETRANGE target is not a string",
			preset:           true,
			key:              "test-int",
			presetValue:      "10",
			command:          []string{"SETRANGE", "test-int", "10", "value"},
			expectedResponse: 0,
			expectedError:    errors.New("value at key test-int is not a string"),
		},
		{
			name:             "Command too short",
			preset:           false,
			command:          []string{"SETRANGE", "key"},
			expectedResponse: 0,
			expectedError:    errors.New(constants.WrongArgsResponse),
		},
		{
			name:             "Command too long",
			preset:           false,
			command:          []string{"SETRANGE", "key", "offset", "value", "value1"},
			expectedResponse: 0,
			expectedError:    errors.New(constants.WrongArgsResponse),
		},
	}

	for i, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			ctx := context.WithValue(context.Background(), "test_name", fmt.Sprintf("SETRANGE, %d", i))

			// If there's a preset step, carry it out here
			if test.preset {
				if _, err := mockServer.CreateKeyAndLock(ctx, test.key); err != nil {
					t.Error(err)
				}
				if err := mockServer.SetValue(ctx, test.key, internal.AdaptType(test.presetValue)); err != nil {
					t.Error(err)
				}
				mockServer.KeyUnlock(ctx, test.key)
			}

			handler := getHandler(test.command[0])
			if handler == nil {
				t.Errorf("no handler found for command %s", test.command[0])
				return
			}

			res, err := handler(getHandlerFuncParams(ctx, test.command, nil))

			if test.expectedError != nil {
				if err.Error() != test.expectedError.Error() {
					t.Errorf("expected error \"%s\", got \"%s\"", test.expectedError.Error(), err.Error())
				}
				return
			}
			if err != nil {
				t.Error(err)
			}
			rd := resp.NewReader(bytes.NewBuffer(res))
			rv, _, err := rd.ReadValue()
			if err != nil {
				t.Error(err)
			}
			if rv.Integer() != test.expectedResponse {
				t.Errorf("expected response \"%d\", got \"%d\"", test.expectedResponse, rv.Integer())
			}

			// Get the value from the echovault and check against the expected value
			if _, err = mockServer.KeyRLock(ctx, test.key); err != nil {
				t.Error(err)
			}
			value, ok := mockServer.GetValue(ctx, test.key).(string)
			if !ok {
				t.Error("expected string data type, got another type")
			}
			if value != test.expectedValue {
				t.Errorf("expected value \"%s\", got \"%s\"", test.expectedValue, value)
			}
			mockServer.KeyRUnlock(ctx, test.key)
		})
	}
}

func Test_HandleStrLen(t *testing.T) {
	tests := []struct {
		name             string
		preset           bool
		key              string
		presetValue      string
		command          []string
		expectedResponse int
		expectedError    error
	}{
		{
			name:             "Return the correct string length for an existing string",
			preset:           true,
			key:              "StrLenKey1",
			presetValue:      "Test String",
			command:          []string{"STRLEN", "StrLenKey1"},
			expectedResponse: len("Test String"),
			expectedError:    nil,
		},
		{
			name:             "If the string does not exist, return 0",
			preset:           false,
			key:              "StrLenKey2",
			presetValue:      "",
			command:          []string{"STRLEN", "StrLenKey2"},
			expectedResponse: 0,
			expectedError:    nil,
		},
		{
			name:             "Too few args",
			preset:           false,
			key:              "StrLenKey3",
			presetValue:      "",
			command:          []string{"STRLEN"},
			expectedResponse: 0,
			expectedError:    errors.New(constants.WrongArgsResponse),
		},
		{
			name:             "Too many args",
			preset:           false,
			key:              "StrLenKey4",
			presetValue:      "",
			command:          []string{"STRLEN", "StrLenKey4", "StrLenKey5"},
			expectedResponse: 0,
			expectedError:    errors.New(constants.WrongArgsResponse),
		},
	}

	for i, test := range tests {
		t.Run(test.name, func(t *testing.T) {
			ctx := context.WithValue(context.Background(), "test_name", fmt.Sprintf("STRLEN, %d", i))

			if test.preset {
				_, err := mockServer.CreateKeyAndLock(ctx, test.key)
				if err != nil {
					t.Error(err)
				}
				if err := mockServer.SetValue(ctx, test.key, test.presetValue); err != nil {
					t.Error(err)
				}
				mockServer.KeyUnlock(ctx, test.key)
			}

			handler := getHandler(test.command[0])
			if handler == nil {
				t.Errorf("no handler found for command %s", test.command[0])
				return
			}

			res, err := handler(getHandlerFuncParams(ctx, test.command, nil))

			if test.expectedError != nil {
				if err.Error() != test.expectedError.Error() {
					t.Errorf("expected error \"%s\", got \"%s\"", test.expectedError.Error(), err.Error())
				}
				return
			}
			rd := resp.NewReader(bytes.NewBuffer(res))
			rv, _, err := rd.ReadValue()
			if err != nil {
				t.Error(err)
			}
			if rv.Integer() != test.expectedResponse {
				t.Errorf("expected respons \"%d\", got \"%d\"", test.expectedResponse, rv.Integer())
			}
		})
	}
}

func Test_HandleSubStr(t *testing.T) {
	tests := []struct {
		name             string
		preset           bool
		key              string
		presetValue      string
		command          []string
		expectedResponse string
		expectedError    error
	}{
		{
			name:             "Return substring within the range of the string",
			preset:           true,
			key:              "SubStrKey1",
			presetValue:      "Test String One",
			command:          []string{"SUBSTR", "SubStrKey1", "5", "10"},
			expectedResponse: "String",
			expectedError:    nil,
		},
		{
			name:             "Return substring at the end of the string with exact end index",
			preset:           true,
			key:              "SubStrKey2",
			presetValue:      "Test String Two",
			command:          []string{"SUBSTR", "SubStrKey2", "12", "14"},
			expectedResponse: "Two",
			expectedError:    nil,
		},
		{
			name:             "Return substring at the end of the string with end index greater than length",
			preset:           true,
			key:              "SubStrKey3",
			presetValue:      "Test String Three",
			command:          []string{"SUBSTR", "SubStrKey3", "12", "75"},
			expectedResponse: "Three",
			expectedError:    nil,
		},
		{
			name:             "Return the substring at the start of the string with 0 start index",
			preset:           true,
			key:              "SubStrKey4",
			presetValue:      "Test String Four",
			command:          []string{"SUBSTR", "SubStrKey4", "0", "3"},
			expectedResponse: "Test",
			expectedError:    nil,
		},
		{
			// Return the substring with negative start index.
			// Substring should begin abs(start) from the end of the string when start is negative.
			name:             "Return the substring with negative start index",
			preset:           true,
			key:              "SubStrKey5",
			presetValue:      "Test String Five",
			command:          []string{"SUBSTR", "SubStrKey5", "-11", "10"},
			expectedResponse: "String",
			expectedError:    nil,
		},
		{
			// Return reverse substring with end index smaller than start index.
			// When end index is smaller than start index, the 2 indices are reversed.
			name:             "Return reverse substring with end index smaller than start index",
			preset:           true,
			key:              "SubStrKey6",
			presetValue:      "Test String Six",
			command:          []string{"SUBSTR", "SubStrKey6", "4", "0"},
			expectedResponse: "tseT",
			expectedError:    nil,
		},
		{
			name:          "Command too short",
			command:       []string{"SUBSTR", "key", "10"},
			expectedError: errors.New(constants.WrongArgsResponse),
		},
		{
			name:          "Command too long",
			command:       []string{"SUBSTR", "key", "10", "15", "20"},
			expectedError: errors.New(constants.WrongArgsResponse),
		},
		{
			name:          "Start index is not an integer",
			command:       []string{"SUBSTR", "key", "start", "10"},
			expectedError: errors.New("start and end indices must be integers"),
		},
		{
			name:          "End index is not an integer",
			command:       []string{"SUBSTR", "key", "0", "end"},
			expectedError: errors.New("start and end indices must be integers"),
		},
		{
			name:          "Non-existent key",
			command:       []string{"SUBSTR", "non-existent-key", "0", "10"},
			expectedError: errors.New("key non-existent-key does not exist"),
		},
	}

	for i, test := range tests {
		t.Run(test.name, func(t *testing.T) {

			ctx := context.WithValue(context.Background(), "test_name", fmt.Sprintf("SUBSTR, %d", i))

			if test.preset {
				if _, err := mockServer.CreateKeyAndLock(ctx, test.key); err != nil {
					t.Error(err)
				}
				if err := mockServer.SetValue(ctx, test.key, test.presetValue); err != nil {
					t.Error(err)
				}
				mockServer.KeyUnlock(ctx, test.key)
			}

			handler := getHandler(test.command[0])
			if handler == nil {
				t.Errorf("no handler found for command %s", test.command[0])
				return
			}

			res, err := handler(getHandlerFuncParams(ctx, test.command, nil))

			if test.expectedError != nil {
				if err.Error() != test.expectedError.Error() {
					t.Errorf("expected error \"%s\", got \"%s\"", test.expectedError.Error(), err.Error())
				}
				return
			}
			rd := resp.NewReader(bytes.NewBuffer(res))
			rv, _, err := rd.ReadValue()
			if err != nil {
				t.Error(err)
			}
			if rv.String() != test.expectedResponse {
				t.Errorf("expected response \"%s\", got \"%s\"", test.expectedResponse, rv.String())
			}
		})
	}
}