using System;
using System.Globalization;
using System.IO;
using System.Text.RegularExpressions;
using Emgu.CV;
using FsCheck;
using FsCheck.Fluent;
using FsCheck.Xunit;
using XplorePlane.Services.Recording;

namespace XplorePlane.Tests.Services
{
    /// <summary>
    /// FsCheck property-based tests for ViewportRecordingService static helpers.
    /// </summary>
    public class ViewportRecordingPropertyTests
    {
        // ── Property 1: Timer formatting correctness ─────────────────────────

        // Feature: viewport-recording, Property 1: Timer formatting correctness
        /// <summary>
        /// **Validates: Requirements 2.2**
        /// For any elapsed time value in seconds between 0 and 3599 (inclusive),
        /// FormatElapsedTime SHALL produce a string in the format "MM:SS" where
        /// MM is zero-padded minutes (00–59) and SS is zero-padded seconds (00–59),
        /// and the numeric value represented equals the input seconds.
        /// </summary>
        [Property(MaxTest = 100)]
        public Property FormatElapsedTime_ProducesCorrectMMSS_ForAllValidSeconds()
        {
            var secondsGen = Gen.Choose(0, 3599);

            return Prop.ForAll(
                secondsGen.ToArbitrary(),
                totalSeconds =>
                {
                    string result = ViewportRecordingService.FormatElapsedTime(totalSeconds);

                    // Verify format is exactly "MM:SS" (5 chars, colon at index 2)
                    bool correctLength = result.Length == 5;
                    bool hasColon = result[2] == ':';
                    bool matchesPattern = Regex.IsMatch(result, @"^\d{2}:\d{2}$");

                    // Parse back and verify numeric correctness
                    int parsedMinutes = int.Parse(result.Substring(0, 2));
                    int parsedSeconds = int.Parse(result.Substring(3, 2));

                    bool minutesInRange = parsedMinutes >= 0 && parsedMinutes <= 59;
                    bool secondsInRange = parsedSeconds >= 0 && parsedSeconds <= 59;

                    // Verify the numeric value equals the input
                    int reconstructed = parsedMinutes * 60 + parsedSeconds;
                    bool valueCorrect = reconstructed == totalSeconds;

                    return correctLength && hasColon && matchesPattern
                        && minutesInRange && secondsInRange && valueCorrect;
                });
        }

        // ── Property 2: Recording filename generation ────────────────────────

        // Feature: viewport-recording, Property 2: Recording filename generation
        /// <summary>
        /// **Validates: Requirements 3.2**
        /// For any valid DateTime value, GenerateFileName SHALL produce a string
        /// matching the pattern REC_yyyyMMdd_HHmmss.mp4, and parsing the timestamp
        /// portion back to a DateTime SHALL yield the same year, month, day, hour,
        /// minute, and second as the input.
        /// </summary>
        [Property(MaxTest = 100)]
        public Property GenerateFileName_MatchesPattern_AndTimestampIsReversible()
        {
            var dateTimeGen = ArbMap.Default.GeneratorFor<DateTime>();

            return Prop.ForAll(
                dateTimeGen.ToArbitrary(),
                (DateTime dateTime) =>
                {
                    var fileName = ViewportRecordingService.GenerateFileName(dateTime);

                    // Verify pattern: REC_yyyyMMdd_HHmmss.mp4
                    var pattern = @"^REC_\d{8}_\d{6}\.mp4$";
                    bool matchesPattern = Regex.IsMatch(fileName, pattern);

                    // Extract timestamp portion and parse back
                    var timestampStr = fileName.Substring(4, 15); // "yyyyMMdd_HHmmss"
                    bool canParse = DateTime.TryParseExact(
                        timestampStr,
                        "yyyyMMdd_HHmmss",
                        CultureInfo.InvariantCulture,
                        DateTimeStyles.None,
                        out DateTime parsed);

                    // Verify reversibility: year, month, day, hour, minute, second match
                    bool isReversible = canParse
                        && parsed.Year == dateTime.Year
                        && parsed.Month == dateTime.Month
                        && parsed.Day == dateTime.Day
                        && parsed.Hour == dateTime.Hour
                        && parsed.Minute == dateTime.Minute
                        && parsed.Second == dateTime.Second;

                    return matchesPattern && isReversible;
                });
        }

        // ── Property 3: VIDEO folder path construction ───────────────────────

        // Feature: viewport-recording, Property 3: VIDEO folder path construction
        /// <summary>
        /// **Validates: Requirements 4.2**
        /// For any non-empty string rootPath, GetVideoFolderPath SHALL produce a path
        /// equal to Path.Combine(rootPath, "VIDEO"), ensuring the VIDEO subfolder
        /// is always constructed relative to the given root path.
        /// </summary>
        [Property(MaxTest = 100)]
        public Property GetVideoFolderPath_AlwaysReturnsVideoSubfolder()
        {
            // Generate non-empty strings (filter out empty/whitespace)
            var nonEmptyStringGen = ArbMap.Default.GeneratorFor<NonEmptyString>();

            return Prop.ForAll(
                nonEmptyStringGen.ToArbitrary(),
                (NonEmptyString rootPath) =>
                {
                    string result = ViewportRecordingService.GetVideoFolderPath(rootPath.Get);

                    // Verify the result equals Path.Combine(rootPath, "VIDEO")
                    string expected = System.IO.Path.Combine(rootPath.Get, "VIDEO");
                    bool equalsExpected = result == expected;

                    // Verify the result ends with "VIDEO" segment
                    bool endsWithVideo = result.EndsWith("VIDEO") || result.EndsWith("VIDEO/") || result.EndsWith("VIDEO\\");

                    return equalsExpected && endsWithVideo;
                });
        }

        // ── Property 4: Null-source frame produces black frame ───────────────

        // Feature: viewport-recording, Property 4: Null-source frame produces black frame
        /// <summary>
        /// **Validates: Requirements 6.3**
        /// For any positive integer dimensions (width, height), CreateBlackFrame SHALL
        /// produce a Mat with the correct dimensions, 3 channels (BGR24), and all pixel
        /// values equal to zero (pure black).
        /// </summary>
        [Property(MaxTest = 50)]
        public Property CreateBlackFrame_ProducesCorrectBlackFrame_ForAnyPositiveDimensions()
        {
            // Generate positive integers for width and height (1..512 to keep tests fast)
            var widthGen = Gen.Choose(1, 512);
            var heightGen = Gen.Choose(1, 512);
            var dimensionsGen = widthGen.SelectMany(w => heightGen.Select(h => (w, h)));

            return Prop.ForAll(
                dimensionsGen.ToArbitrary(),
                ((int width, int height) dims) =>
                {
                    using var frame = ViewportRecordingService.CreateBlackFrame(dims.width, dims.height);

                    // Verify dimensions
                    bool correctWidth = frame.Width == dims.width;
                    bool correctHeight = frame.Height == dims.height;

                    // Verify 3 channels (BGR24)
                    bool correctChannels = frame.NumberOfChannels == 3;

                    // Verify all pixels are zero (black)
                    // Get raw byte data and check all zeros
                    int totalBytes = dims.width * dims.height * 3;
                    byte[] pixelData = new byte[totalBytes];
                    System.Runtime.InteropServices.Marshal.Copy(frame.DataPointer, pixelData, 0, totalBytes);
                    bool allZero = System.Array.TrueForAll(pixelData, b => b == 0);

                    return correctWidth && correctHeight && correctChannels && allZero;
                });
        }
    }
}