/// Enumeration of all System Calls (Syscalls) available in the Prometeu environment.
///
/// Syscalls are the primary mechanism for a program running in the Virtual Machine 
/// to interact with the outside world (Hardware, OS, Filesystem). 
/// 
/// Each Syscall has a unique 32-bit ID. The IDs are grouped by category:
/// - **0x0xxx**: System & OS Control
/// - **0x1xxx**: Graphics (GFX)
/// - **0x2xxx**: Input (Gamepad & Touch)
/// - **0x3xxx**: Audio (PCM & Mixing)
/// - **0x4xxx**: Filesystem (Sandboxed I/O)
/// - **0x5xxx**: Logging & Debugging
/// - **0x6xxx**: Asset Loading & Memory Banks
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[repr(u32)]
pub enum Syscall {
    // --- System ---
    /// Checks if a cartridge is currently inserted in the virtual slot.
    SystemHasCart = 0x0001,
    /// Requests the OS to launch a specific cartridge.
    SystemRunCart = 0x0002,

    // --- GFX (Graphics) ---
    /// Fills the entire back buffer with a single color.
    GfxClear = 0x1001,
    /// Draws a solid rectangle.
    GfxFillRect = 0x1002,
    /// Draws a 1-pixel wide line.
    GfxDrawLine = 0x1003,
    /// Draws a circle outline.
    GfxDrawCircle = 0x1004,
    /// Draws a filled circle (disc).
    GfxDrawDisc = 0x1005,
    /// Draws a rectangle outline.
    GfxDrawSquare = 0x1006,
    /// Configures one of the 512 hardware sprites.
    GfxSetSprite = 0x1007,
    /// Draws a text string at the specified coordinates.
    GfxDrawText = 0x1008,
    /// Fills the entire back buffer with a single RGB565 color (flattened).
    GfxClear565 = 0x1010,

    // --- Input ---
    /// Returns the current raw state of the digital gamepad (bitmask).
    InputGetPad = 0x2001,
    /// Returns buttons that were pressed exactly in this frame.
    InputGetPadPressed = 0x2002,
    /// Returns buttons that were released exactly in this frame.
    InputGetPadReleased = 0x2003,
    /// Returns how many frames a button has been held down.
    InputGetPadHold = 0x2004,
    /// Returns the full snapshot of the gamepad state (48 slots).
    InputPadSnapshot = 0x2010,
    /// Returns the full snapshot of the touch state (6 slots).
    InputTouchSnapshot = 0x2011,

    /// Returns the X coordinate of the touch/mouse pointer.
    TouchGetX = 0x2101,
    /// Returns the Y coordinate of the touch/mouse pointer.
    TouchGetY = 0x2102,
    /// Returns true if the pointer is currently touching the screen.
    TouchIsDown = 0x2103,
    /// Returns true if the touch started in this frame.
    TouchIsPressed = 0x2104,
    /// Returns true if the touch ended in this frame.
    TouchIsReleased = 0x2105,
    /// Returns how many frames the pointer has been held down.
    TouchGetHold = 0x2106,
    /// Returns the full Button struct (6 bytes) for the touch finger state.
    TouchGetFinger = 0x2107,

    // --- Input (Pad service-based) ---
    /// Returns the full Button struct (6 bytes) for each gamepad button
    PadGetUp = 0x2200,
    PadGetDown = 0x2201,
    PadGetLeft = 0x2202,
    PadGetRight = 0x2203,
    PadGetA = 0x2204,
    PadGetB = 0x2205,
    PadGetX = 0x2206,
    PadGetY = 0x2207,
    PadGetL = 0x2208,
    PadGetR = 0x2209,
    PadGetStart = 0x220A,
    PadGetSelect = 0x220B,

    // --- Audio ---
    /// Starts playback of a sound sample by its Bank and ID.
    AudioPlaySample = 0x3001,
    /// Low-level audio play command.
    AudioPlay = 0x3002,

    // --- FS (Filesystem) ---
    /// Opens a file for reading or writing. Returns a File Handle (u32).
    FsOpen = 0x4001,
    /// Reads data from an open file handle into the VM heap.
    FsRead = 0x4002,
    /// Writes data from the VM heap into an open file handle.
    FsWrite = 0x4003,
    /// Closes an open file handle.
    FsClose = 0x4004,
    /// Lists entries in a directory.
    FsListDir = 0x4005,
    /// Checks if a file or directory exists.
    FsExists = 0x4006,
    /// Deletes a file or empty directory.
    FsDelete = 0x4007,

    // --- Log ---
    /// Writes a generic string to the system log.
    LogWrite = 0x5001,
    /// Writes a string to the system log with a specific numerical tag.
    LogWriteTag = 0x5002,

    // --- Asset (DMA) ---
    /// Starts an asynchronous load of a file into a memory bank.
    AssetLoad = 0x6001,
    /// Returns the status of a pending asset load (0=Loading, 1=Ready, 2=Error).
    AssetStatus = 0x6002,
    /// Finalizes the asset loading, making it available for GFX/Audio.
    AssetCommit = 0x6003,
    /// Cancels a pending asset load.
    AssetCancel = 0x6004,

    // --- Bank (Memory) ---
    /// Returns information about a specific Memory Bank.
    BankInfo = 0x6101,
    /// Returns information about a slot within a Memory Bank.
    BankSlotInfo = 0x6102,
}

impl Syscall {
    pub fn from_u32(id: u32) -> Option<Self> {
        match id {
            0x0001 => Some(Self::SystemHasCart),
            0x0002 => Some(Self::SystemRunCart),
            0x1001 => Some(Self::GfxClear),
            0x1002 => Some(Self::GfxFillRect),
            0x1003 => Some(Self::GfxDrawLine),
            0x1004 => Some(Self::GfxDrawCircle),
            0x1005 => Some(Self::GfxDrawDisc),
            0x1006 => Some(Self::GfxDrawSquare),
            0x1007 => Some(Self::GfxSetSprite),
            0x1008 => Some(Self::GfxDrawText),
            0x1010 => Some(Self::GfxClear565),
            0x2001 => Some(Self::InputGetPad),
            0x2002 => Some(Self::InputGetPadPressed),
            0x2003 => Some(Self::InputGetPadReleased),
            0x2004 => Some(Self::InputGetPadHold),
            0x2010 => Some(Self::InputPadSnapshot),
            0x2011 => Some(Self::InputTouchSnapshot),
            0x2101 => Some(Self::TouchGetX),
            0x2102 => Some(Self::TouchGetY),
            0x2103 => Some(Self::TouchIsDown),
            0x2104 => Some(Self::TouchIsPressed),
            0x2105 => Some(Self::TouchIsReleased),
            0x2106 => Some(Self::TouchGetHold),
            0x2107 => Some(Self::TouchGetFinger),
            0x2200 => Some(Self::PadGetUp),
            0x2201 => Some(Self::PadGetDown),
            0x2202 => Some(Self::PadGetLeft),
            0x2203 => Some(Self::PadGetRight),
            0x2204 => Some(Self::PadGetA),
            0x2205 => Some(Self::PadGetB),
            0x2206 => Some(Self::PadGetX),
            0x2207 => Some(Self::PadGetY),
            0x2208 => Some(Self::PadGetL),
            0x2209 => Some(Self::PadGetR),
            0x220A => Some(Self::PadGetStart),
            0x220B => Some(Self::PadGetSelect),
            0x3001 => Some(Self::AudioPlaySample),
            0x3002 => Some(Self::AudioPlay),
            0x4001 => Some(Self::FsOpen),
            0x4002 => Some(Self::FsRead),
            0x4003 => Some(Self::FsWrite),
            0x4004 => Some(Self::FsClose),
            0x4005 => Some(Self::FsListDir),
            0x4006 => Some(Self::FsExists),
            0x4007 => Some(Self::FsDelete),
            0x5001 => Some(Self::LogWrite),
            0x5002 => Some(Self::LogWriteTag),
            0x6001 => Some(Self::AssetLoad),
            0x6002 => Some(Self::AssetStatus),
            0x6003 => Some(Self::AssetCommit),
            0x6004 => Some(Self::AssetCancel),
            0x6101 => Some(Self::BankInfo),
            0x6102 => Some(Self::BankSlotInfo),
            _ => None,
        }
    }

    pub fn args_count(&self) -> usize {
        match self {
            Self::SystemHasCart => 0,
            Self::SystemRunCart => 0,
            Self::GfxClear => 1,
            Self::GfxFillRect => 5,
            Self::GfxDrawLine => 5,
            Self::GfxDrawCircle => 4,
            Self::GfxDrawDisc => 5,
            Self::GfxDrawSquare => 6,
            Self::GfxSetSprite => 10,
            Self::GfxDrawText => 4,
            Self::GfxClear565 => 1,
            Self::InputGetPad => 1,
            Self::InputGetPadPressed => 1,
            Self::InputGetPadReleased => 1,
            Self::InputGetPadHold => 1,
            Self::InputPadSnapshot => 0,
            Self::InputTouchSnapshot => 0,
            Self::TouchGetX => 0,
            Self::TouchGetY => 0,
            Self::TouchIsDown => 0,
            Self::TouchIsPressed => 0,
            Self::TouchIsReleased => 0,
            Self::TouchGetHold => 0,
            Self::TouchGetFinger => 0,
            Self::PadGetUp => 0,
            Self::PadGetDown => 0,
            Self::PadGetLeft => 0,
            Self::PadGetRight => 0,
            Self::PadGetA => 0,
            Self::PadGetB => 0,
            Self::PadGetX => 0,
            Self::PadGetY => 0,
            Self::PadGetL => 0,
            Self::PadGetR => 0,
            Self::PadGetStart => 0,
            Self::PadGetSelect => 0,
            Self::AudioPlaySample => 5,
            Self::AudioPlay => 7,
            Self::FsOpen => 1,
            Self::FsRead => 1,
            Self::FsWrite => 2,
            Self::FsClose => 1,
            Self::FsListDir => 1,
            Self::FsExists => 1,
            Self::FsDelete => 1,
            Self::LogWrite => 2,
            Self::LogWriteTag => 3,
            Self::AssetLoad => 3,
            Self::AssetStatus => 1,
            Self::AssetCommit => 1,
            Self::AssetCancel => 1,
            Self::BankInfo => 1,
            Self::BankSlotInfo => 2,
        }
    }

    pub fn results_count(&self) -> usize {
        match self {
            // --- System ---
            Self::SystemHasCart => 1,
            Self::SystemRunCart => 0,

            // --- GFX (void) ---
            Self::GfxClear => 0,
            Self::GfxFillRect => 0,
            Self::GfxDrawLine => 0,
            Self::GfxDrawCircle => 0,
            Self::GfxDrawDisc => 0,
            Self::GfxDrawSquare => 0,
            Self::GfxSetSprite => 0,
            Self::GfxDrawText => 0,
            Self::GfxClear565 => 0,

            // --- Input (scalar/snapshots) ---
            Self::InputGetPad => 1,
            Self::InputGetPadPressed => 1,
            Self::InputGetPadReleased => 1,
            Self::InputGetPadHold => 1,
            Self::InputPadSnapshot => 48,
            Self::InputTouchSnapshot => 6,

            // --- Touch (scalars/struct) ---
            Self::TouchGetX => 1,
            Self::TouchGetY => 1,
            Self::TouchIsDown => 1,
            Self::TouchIsPressed => 1,
            Self::TouchIsReleased => 1,
            Self::TouchGetHold => 1,
            Self::TouchGetFinger => 4, // Button struct (4 slots)

            // --- Pad (per-button struct: 4 slots) ---
            Self::PadGetUp
            | Self::PadGetDown
            | Self::PadGetLeft
            | Self::PadGetRight
            | Self::PadGetA
            | Self::PadGetB
            | Self::PadGetX
            | Self::PadGetY
            | Self::PadGetL
            | Self::PadGetR
            | Self::PadGetStart
            | Self::PadGetSelect => 4,

            // --- Audio (void) ---
            Self::AudioPlaySample => 0,
            Self::AudioPlay => 0,

            // --- FS ---
            Self::FsOpen => 1,
            Self::FsRead => 1,   // bytes read
            Self::FsWrite => 1,  // bytes written
            Self::FsClose => 0,
            Self::FsListDir => 1, // entries count/handle (TBD)
            Self::FsExists => 1,
            Self::FsDelete => 0,

            // --- Log (void) ---
            Self::LogWrite | Self::LogWriteTag => 0,

            // --- Asset/Bank (conservador) ---
            Self::AssetLoad => 1,
            Self::AssetStatus => 1,
            Self::AssetCommit => 0,
            Self::AssetCancel => 0,
            Self::BankInfo => 1,
            Self::BankSlotInfo => 1,
        }
    }

    pub fn name(&self) -> &'static str {
        match self {
            Self::SystemHasCart => "SystemHasCart",
            Self::SystemRunCart => "SystemRunCart",
            Self::GfxClear => "GfxClear",
            Self::GfxFillRect => "GfxFillRect",
            Self::GfxDrawLine => "GfxDrawLine",
            Self::GfxDrawCircle => "GfxDrawCircle",
            Self::GfxDrawDisc => "GfxDrawDisc",
            Self::GfxDrawSquare => "GfxDrawSquare",
            Self::GfxSetSprite => "GfxSetSprite",
            Self::GfxDrawText => "GfxDrawText",
            Self::GfxClear565 => "GfxClear565",
            Self::InputGetPad => "InputGetPad",
            Self::InputGetPadPressed => "InputGetPadPressed",
            Self::InputGetPadReleased => "InputGetPadReleased",
            Self::InputGetPadHold => "InputGetPadHold",
            Self::InputPadSnapshot => "InputPadSnapshot",
            Self::InputTouchSnapshot => "InputTouchSnapshot",
            Self::TouchGetX => "TouchGetX",
            Self::TouchGetY => "TouchGetY",
            Self::TouchIsDown => "TouchIsDown",
            Self::TouchIsPressed => "TouchIsPressed",
            Self::TouchIsReleased => "TouchIsReleased",
            Self::TouchGetHold => "TouchGetHold",
            Self::TouchGetFinger => "TouchGetFinger",
            Self::PadGetUp => "PadGetUp",
            Self::PadGetDown => "PadGetDown",
            Self::PadGetLeft => "PadGetLeft",
            Self::PadGetRight => "PadGetRight",
            Self::PadGetA => "PadGetA",
            Self::PadGetB => "PadGetB",
            Self::PadGetX => "PadGetX",
            Self::PadGetY => "PadGetY",
            Self::PadGetL => "PadGetL",
            Self::PadGetR => "PadGetR",
            Self::PadGetStart => "PadGetStart",
            Self::PadGetSelect => "PadGetSelect",
            Self::AudioPlaySample => "AudioPlaySample",
            Self::AudioPlay => "AudioPlay",
            Self::FsOpen => "FsOpen",
            Self::FsRead => "FsRead",
            Self::FsWrite => "FsWrite",
            Self::FsClose => "FsClose",
            Self::FsListDir => "FsListDir",
            Self::FsExists => "FsExists",
            Self::FsDelete => "FsDelete",
            Self::LogWrite => "LogWrite",
            Self::LogWriteTag => "LogWriteTag",
            Self::AssetLoad => "AssetLoad",
            Self::AssetStatus => "AssetStatus",
            Self::AssetCommit => "AssetCommit",
            Self::AssetCancel => "AssetCancel",
            Self::BankInfo => "BankInfo",
            Self::BankSlotInfo => "BankSlotInfo",
        }
    }
}