// ---------------------------------------------------------------------------
// PCI config space — legacy port-based access (0xCF8 / 0xCFC).
//
// Enumeration walks buses 0-255 × devices 0-31 × functions 0-7.  Port I/O
// stays usable after ExitBootServices, so the shell can list devices and
// future drivers (AHCI, network, ...) can find their controllers.
// ---------------------------------------------------------------------------

const CONFIG_ADDRESS: u16 = 0xCF8;
const CONFIG_DATA: u16 = 0xCFC;

#[derive(Debug, Clone, Copy)]
pub struct DeviceInfo {
    pub bus: u8,
    pub device: u8,
    pub func: u8,
    pub vendor: u16,
    pub device_id: u16,
    pub class: u8,
    pub subclass: u8,
    pub prog_if: u8,
    pub header_type: u8,
}

fn outl(port: u16, val: u32) {
    unsafe {
        core::arch::asm!(
            "out dx, eax",
            in("dx") port,
            in("eax") val,
            options(nomem, nostack, preserves_flags)
        );
    }
}

fn inl(port: u16) -> u32 {
    let val: u32;
    unsafe {
        core::arch::asm!(
            "in eax, dx",
            out("eax") val,
            in("dx") port,
            options(nomem, nostack, preserves_flags)
        );
    }
    val
}

/// Encode the PCI config-space port address for (bus, dev, fn, reg);
/// `reg` must be dword-aligned.
fn config_addr(bus: u8, device: u8, func: u8, reg: u8) -> u32 {
    0x8000_0000
        | ((bus as u32) << 16)
        | ((device as u32) << 11)
        | ((func as u32) << 8)
        | ((reg as u32) & 0xFC)
}

/// Read a dword from a device's config space (`reg` must be dword-aligned).
pub fn config_read(bus: u8, device: u8, func: u8, reg: u8) -> u32 {
    outl(CONFIG_ADDRESS, config_addr(bus, device, func, reg));
    inl(CONFIG_DATA)
}
/// Write a dword to a device's config space (`reg` must be dword-aligned).
pub fn config_write(bus: u8, device: u8, func: u8, reg: u8, val: u32) {
    outl(CONFIG_ADDRESS, config_addr(bus, device, func, reg));
    outl(CONFIG_DATA, val)
}

fn outb(port: u16, val: u8) {
    unsafe {
        core::arch::asm!(
            "out dx, al",
            in("dx") port,
            in("al") val,
            options(nomem, nostack, preserves_flags)
        );
    }
}

/// Write a single byte to config space (any byte offset).  The PCI
/// byte-enable cycle goes out on port 0xCFC + lane, exactly like `pci_
/// write_config_byte` everywhere else; QEMU and real chipsets both decode
/// the low two address bits of the config-data port.
pub fn config_write_byte(bus: u8, device: u8, func: u8, reg: u8, val: u8) {
    outl(CONFIG_ADDRESS, config_addr(bus, device, func, reg));
    outb(CONFIG_DATA + ((reg & 3) as u16), val)
}

/// Read a memory BAR (index 0-5) as a 64-bit address, handling 32/64-bit
/// BARs.  Returns None for I/O BARs or invalid values.
pub fn bar64(bus: u8, device: u8, func: u8, bar_index: u8) -> Option<u64> {
    let reg_off = 0x10 + bar_index * 4;
    let lo = config_read(bus, device, func, reg_off);
    if lo & 1 == 1 {
        return None; // I/O BAR
    }
    let kind = (lo >> 1) & 0x3;
    let hi = if kind == 2 {
        config_read(bus, device, func, reg_off + 4)
    } else {
        0
    };
    let base = ((hi as u64) << 32) | (lo as u64 & 0xFFFF_FFF0);
    if base == 0 {
        None
    } else {
        Some(base)
    }
}

/// Claim USB Legacy ownership from the BIOS on a controller whose MMIO base
/// exposes the USB Legacy Support extended capability (USBLEGSUP, cap id 1).
///
/// EHCI/xHCI “USB Legacy Support” ownership handoff (EHCI spec §5.1).
///
/// The 2012-era PCH BIOS drives USB keyboards through SMM USB-legacy
/// emulation while it owns the controller: its SMI handler polls the EHCI
/// over USB-error/port-change events.  If the OS reprograms the controller
/// and runs async DMA underneath the still-active BIOS module, the SMM poll
/// collides with the OS transfer at an unpredictable moment — a classic
/// real-silicon Host System Error (SE) that QEMU cannot reproduce (no SMM).
///
/// CRITICAL: the extended-capability pointer is a PCI *config-space*
/// offset, not an MMIO offset.  Read it from an MMIO register (`eccp_src`
/// = MMIO dword offset; EHCI: HCCPARAMS @+0x08 bits 15:8; xHCI: HCSPARAMS1
/// @+0x04 bits 31:16), then walk config space — exactly Linux's
/// `quirk_usb_handoff_ehci` (pci-quirks.c) and FreeBSD's `ehci_pci_attach`.
/// Our previous implementation treated EECP as an MMIO offset, read a
/// reserved register (0), and silently never claimed ownership — the
/// observed “claim skipped” on the 7010.
///
/// Handshake (Linux/FreeBSD-identical): if the BIOS-owned semaphore
/// (bit 16 of the cap dword) is set, write the OS-owned semaphore byte
/// (cap+3) = 1 and spin (bounded ~1 s) for bit 16 to clear.  USBLEGCTLSTS
/// (cap+4) is deliberately left alone — Linux notes some systems “get
/// upset” if it's touched.
///
/// Returns: 0 = already released/owned (no claim needed), 1 = handed over,
/// 2 = BIOS never released, 3 = no legacy capability / chain out of range.
pub fn claim_usb_legacy(
    bus: u8,
    dev: u8,
    func: u8,
    mmio_base: usize,
    eccp_src: usize,
    eccp_bits_high: bool,
) -> u8 {
    let src = unsafe { (mmio_base as *const u32).add(eccp_src).read_volatile() };
    crate::serial_println!(
        "usb-legacy: probe mmio=+{:#x} hcc={:#010x} high={}",
        eccp_src,
        src,
        eccp_bits_high
    );
    let mut offset = if eccp_bits_high {
        ((src >> 16) & 0xFFFF) as u8 // xHCI: XECP (u8 caps the walk at 0xFF config)
    } else {
        ((src >> 8) & 0xFF) as u8 // EHCI: EECP
    };
    if offset == 0 {
        return 3;
    }
    let mut guard = 32; // bounded walk, no panics
    while offset != 0 && guard > 0 {
        guard -= 1;
        let cap = config_read(bus, dev, func, offset);
        crate::serial_println!(
            "usb-legacy: cap@{:#x} id={:#04x} next={:#04x} d={:#010x}",
            offset,
            cap & 0xFF,
            (cap >> 8) & 0xFF,
            cap
        );
        let id = cap & 0xFF;
        let next = ((cap >> 8) & 0xFF) as u8;
        match id {
            0 => return 3, // illegal reserved cap terminates the chain
            1 => {
                // USB Legacy Support capability.
                let ctlsts = config_read(bus, dev, func, offset + 4);
                crate::serial_println!(
                    "usb-legacy: cap@{:#x} bios_sem={} os_sem={} ctlsts={:#x}",
                    offset,
                    (cap >> 16) & 1,
                    (cap >> 24) & 1,
                    ctlsts
                );
                if cap & (1 << 24) != 0 {
                    return 0; // OS already owns
                }
                if cap & (1 << 16) == 0 {
                    return 0; // BIOS not claiming it
                }
                crate::serial_println!("usb-legacy: BIOS owns controller - claiming (OS sem)");
                config_write_byte(bus, dev, func, offset + 3, 1);
                let t0 = crate::interrupts::uptime_ms();
                let mut handed = false;
                while crate::interrupts::uptime_ms().wrapping_sub(t0) < 1000 {
                    if config_read(bus, dev, func, offset) & (1 << 16) == 0 {
                        handed = true;
                        break;
                    }
                    core::hint::spin_loop();
                }
                return if handed { 1 } else { 2 };
            }
            _ => {
                offset = next;
            }
        }
    }
    3
}

/// Enumerate every device/function present on all buses.
pub fn probe() -> alloc::vec::Vec<DeviceInfo> {
    let mut out = alloc::vec::Vec::new();
    for bus in 0..=255u8 {
        for dev in 0..32u8 {
            for func in 0..8u8 {
                let id = config_read(bus, dev, func, 0);
                let vendor = (id & 0xFFFF) as u16;
                if vendor == 0xFFFF {
                    if func == 0 {
                        break; // nothing on this device number
                    }
                    continue;
                }
                let hdr = config_read(bus, dev, func, 0x0C);
                let header_type = (hdr & 0xFF) as u8;
                let cc = config_read(bus, dev, func, 0x08);
                out.push(DeviceInfo {
                    bus,
                    device: dev,
                    func,
                    vendor,
                    device_id: (id >> 16) as u16,
                    class: (cc >> 24) as u8,
                    subclass: (cc >> 16) as u8,
                    prog_if: (cc >> 8) as u8,
                    header_type,
                });
                // A non-multifunction device has no functions 1-7.
                if func == 0 && header_type & 0x80 == 0 {
                    break;
                }
            }
        }
    }
    out
}

/// Short human name for a (class, subclass) pair.
pub fn class_name(class: u8, subclass: u8) -> &'static str {
    match (class, subclass) {
        (0x00, 0x01) => "VGA-compatible",
        (0x00, _) => "Unclassified",
        (0x01, 0x01) => "IDE controller",
        (0x01, 0x06) => "SATA controller",
        (0x01, 0x08) => "NVM controller",
        (0x01, _) => "Mass storage",
        (0x02, 0x00) => "Ethernet",
        (0x02, _) => "Network",
        (0x03, 0x00) => "VGA",
        (0x03, _) => "Display",
        (0x04, _) => "Multimedia",
        (0x05, _) => "Memory controller",
        (0x06, 0x00) => "Host bridge",
        (0x06, 0x01) => "ISA bridge",
        (0x06, 0x04) => "PCI-PCI bridge",
        (0x06, _) => "Bridge",
        (0x08, 0x80) => "PIC",
        (0x0C, 0x03) => "USB controller",
        (0x0C, 0x05) => "SMBus",
        (0x0C, _) => "Serial bus",
        (0x11, _) => "Signal processing",
        (0xFF, _) => "Unassigned",
        _ => "Other",
    }
}