package main

import (
	"testing"
)

func TestParseMsg(t *testing.T) {
	tests := []struct {
		name      string
		input     string
		wantID    int
		wantData  []string
		wantError bool
	}{
		{
			name:      "valid message with single data element",
			input:     "M01,25.5",
			wantID:    1,
			wantData:  []string{"25.5"},
			wantError: false,
		},
		{
			name:      "valid message with multiple data elements",
			input:     "M02,25.5,60,1013",
			wantID:    2,
			wantData:  []string{"25.5", "60", "1013"},
			wantError: false,
		},
		{
			name:      "valid message with ID only",
			input:     "M0",
			wantID:    0,
			wantData:  []string{},
			wantError: false,
		},
		{
			name:      "invalid message with non-numeric ID",
			input:     "Mabc,data",
			wantID:    0,
			wantData:  nil,
			wantError: true,
		},
		{
			name:      "invalid message with missing M prefix",
			input:     "1,data",
			wantID:    0,
			wantData:  nil,
			wantError: true,
		},
		{
			name:      "invalid message with empty string",
			input:     "",
			wantID:    0,
			wantData:  nil,
			wantError: true,
		},
		{
			name:      "valid message with empty data elements",
			input:     "M5,,data,,",
			wantID:    5,
			wantData:  []string{"", "data", "", ""},
			wantError: false,
		},
		{
			name:      "valid message with special characters in data",
			input:     "M10,key=value!@#$",
			wantID:    10,
			wantData:  []string{"key=value!@#$"},
			wantError: false,
		},
		{
			name:      "newlines and whitespace are stripped from data",
			input:     "M1,1.0,1.1,1.2\n",
			wantID:    1,
			wantData:  []string{"1.0", "1.1", "1.2"},
			wantError: false,
		},
		{
			name:      "leading and trailing whitespace stripped",
			input:     "M5, data1 , data2 \t, data3\r\n",
			wantID:    5,
			wantData:  []string{"data1", "data2", "data3"},
			wantError: false,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			got, err := ParseMsg(tt.input)

			if (err != nil) != tt.wantError {
				t.Errorf("ParseMsg() error = %v, wantError %v", err, tt.wantError)
				return
			}

			if tt.wantError {
				return
			}

			if got.ID != tt.wantID {
				t.Errorf("ParseMsg() ID = %d, want %d", got.ID, tt.wantID)
			}

			if len(got.Data) != len(tt.wantData) {
				t.Errorf("ParseMsg() data length = %d, want %d", len(got.Data), len(tt.wantData))
				return
			}

			for i, val := range got.Data {
				if val != tt.wantData[i] {
					t.Errorf("ParseMsg() data[%d] = %q, want %q", i, val, tt.wantData[i])
				}
			}
		})
	}
}