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use crate::{
    namespace::AmlName,
    resource::{self, InterruptPolarity, InterruptTrigger, Resource},
    value::Args,
    AmlContext,
    AmlError,
    AmlType,
    AmlValue,
};
use alloc::vec::Vec;
use bit_field::BitField;
use core::convert::TryInto;

pub use crate::resource::IrqDescriptor;

#[derive(Clone, Copy, PartialEq, Eq, Debug)]
pub enum Pin {
    IntA,
    IntB,
    IntC,
    IntD,
}

#[derive(Debug)]
pub enum PciRouteType {
    /// The interrupt is hard-coded to a specific GSI
    Gsi(u32),

    /// The interrupt is linked to a link object. This object will have `_PRS`, `_CRS` fields and a `_SRS` method
    /// that can be used to allocate the interrupt. Note that some platforms (e.g. QEMU's q35 chipset) use link
    /// objects but do not support changing the interrupt that it's linked to (i.e. `_SRS` doesn't do anything).
    /*
     * The actual object itself will just be a `Device`, and we need paths to its children objects to do
     * anything useful, so we just store the resolved name here.
     */
    LinkObject(AmlName),
}

#[derive(Debug)]
pub struct PciRoute {
    device: u16,
    function: u16,
    pin: Pin,
    route_type: PciRouteType,
}

/// A `PciRoutingTable` is used to interpret the data in a `_PRT` object, which provides a mapping
/// from PCI interrupt pins to the inputs of the interrupt controller. One of these objects must be
/// present under each PCI root bridge, and consists of a package of packages, each of which describes the
/// mapping of a single PCI interrupt pin.
#[derive(Debug)]
pub struct PciRoutingTable {
    entries: Vec<PciRoute>,
}

impl PciRoutingTable {
    /// Construct a `PciRoutingTable` from a path to a `_PRT` object. Returns
    /// `AmlError::IncompatibleValueConversion` if the value passed is not a package, or if any of the values
    /// within it are not packages. Returns the various `AmlError::Prt*` errors if the internal structure of the
    /// entries is invalid.
    pub fn from_prt_path(prt_path: &AmlName, context: &mut AmlContext) -> Result<PciRoutingTable, AmlError> {
        let mut entries = Vec::new();

        let prt = context.invoke_method(&prt_path, Args::default())?;
        if let AmlValue::Package(ref inner_values) = prt {
            for value in inner_values {
                if let AmlValue::Package(ref pin_package) = value {
                    /*
                     * Each inner package has the following structure:
                     *   | Field      | Type      | Description                                               |
                     *   | -----------|-----------|-----------------------------------------------------------|
                     *   | Address    | Dword     | Address of the device. Same format as _ADR objects (high  |
                     *   |            |           | word = #device, low word = #function)                     |
                     *   | -----------|-----------|-----------------------------------------------------------|
                     *   | Pin        | Byte      | The PCI pin (0 = INTA, 1 = INTB, 2 = INTC, 3 = INTD)      |
                     *   | -----------|-----------|-----------------------------------------------------------|
                     *   | Source     | Byte or   | Name of the device that allocates the interrupt to which  |
                     *   |            | NamePath  | the above pin is connected. Can be fully qualified,       |
                     *   |            |           | relative, or a simple NameSeg that utilizes namespace     |
                     *   |            |           | search rules. Instead, if this is a byte value of 0, the  |
                     *   |            |           | interrupt is allocated out of the GSI pool, and Source    |
                     *   |            |           | Index should be utilised.                                 |
                     *   | -----------|-----------|-----------------------------------------------------------|
                     *   | Source     | Dword     | Index that indicates which resource descriptor in the     |
                     *   | Index      |           | resource template of the device pointed to in the Source  |
                     *   |            |           | field this interrupt is allocated from. If the Source     |
                     *   |            |           | is zero, then this field is the GSI number to which the   |
                     *   |            |           | pin is connected.                                         |
                     *   | -----------|-----------|-----------------------------------------------------------|
                     */
                    let address = pin_package[0].as_integer(context)?;
                    let device = address.get_bits(16..32).try_into().map_err(|_| AmlError::PrtInvalidAddress)?;
                    let function = address.get_bits(0..16).try_into().map_err(|_| AmlError::PrtInvalidAddress)?;
                    let pin = match pin_package[1].as_integer(context)? {
                        0 => Pin::IntA,
                        1 => Pin::IntB,
                        2 => Pin::IntC,
                        3 => Pin::IntD,
                        _ => return Err(AmlError::PrtInvalidPin),
                    };

                    match pin_package[2] {
                        AmlValue::Integer(0) => {
                            /*
                             * The Source Index field contains the GSI number that this interrupt is attached
                             * to.
                             */
                            entries.push(PciRoute {
                                device,
                                function,
                                pin,
                                route_type: PciRouteType::Gsi(
                                    pin_package[3]
                                        .as_integer(context)?
                                        .try_into()
                                        .map_err(|_| AmlError::PrtInvalidGsi)?,
                                ),
                            });
                        }
                        AmlValue::String(ref name) => {
                            let link_object_name =
                                context.namespace.search_for_level(&AmlName::from_str(name)?, &prt_path)?;
                            entries.push(PciRoute {
                                device,
                                function,
                                pin,
                                route_type: PciRouteType::LinkObject(link_object_name),
                            });
                        }
                        _ => return Err(AmlError::PrtInvalidSource),
                    }
                } else {
                    return Err(AmlError::IncompatibleValueConversion {
                        current: value.type_of(),
                        target: AmlType::Package,
                    });
                }
            }

            Ok(PciRoutingTable { entries })
        } else {
            Err(AmlError::IncompatibleValueConversion { current: prt.type_of(), target: AmlType::Package })
        }
    }

    /// Get the interrupt input that a given PCI interrupt pin is wired to. Returns `AmlError::PrtNoEntry` if the
    /// PRT doesn't contain an entry for the given address + pin.
    pub fn route(
        &self,
        device: u16,
        function: u16,
        pin: Pin,
        context: &mut AmlContext,
    ) -> Result<IrqDescriptor, AmlError> {
        let entry = self
            .entries
            .iter()
            .find(|entry| {
                entry.device == device
                    && (entry.function == 0xffff || entry.function == function)
                    && entry.pin == pin
            })
            .ok_or(AmlError::PrtNoEntry)?;

        match entry.route_type {
            PciRouteType::Gsi(gsi) => Ok(IrqDescriptor {
                is_consumer: true,
                trigger: InterruptTrigger::Level,
                polarity: InterruptPolarity::ActiveLow,
                is_shared: true,
                is_wake_capable: false,
                irq: gsi,
            }),
            PciRouteType::LinkObject(ref name) => {
                let link_crs =
                    context.namespace.get_by_path(&AmlName::from_str("_CRS").unwrap().resolve(name)?)?;

                let resources = resource::resource_descriptor_list(link_crs)?;
                match resources.as_slice() {
                    [Resource::Irq(descriptor)] => Ok(descriptor.clone()),
                    _ => Err(AmlError::UnexpectedResourceType),
                }
            }
        }
    }
}