use crate::ecall::SbiRet;
use crate::util::OnceFatBox;
use alloc::boxed::Box;

/// Performance Monitoring Unit Extension
///
/// The RISC-V hardware performance counters such as `mcycle`, `minstret`, and `mhpmcounterX` CSRs
/// are accessible as read-only from supervisor-mode using `cycle`, `instret`, and `hpmcounterX` CSRs.
/// The SBI performance monitoring unit (PMU) extension is an interface for supervisor-mode to configure
/// and use the RISC-V hardware performance counters with assistance from the machine-mode (or hypervisor-mode).
/// These hardware performance counters can only be started, stopped, or configured from machine-mode
/// using `mcountinhibit` and `mhpmeventX` CSRs.
/// Due to this, a machine-mode SBI implementation may choose to disallow SBI PMU extension
/// if `mcountinhibit` CSR is not implemented by the RISC-V platform.
///
/// A RISC-V platform generally supports monitoring of various hardware events using a limited number
/// of hardware performance counters which are up to 64 bits wide.
/// In addition, a SBI implementation can also provide firmware performance counters which can monitor firmware events
/// such as number of misaligned load/store instructions, number of RFENCEs, number of IPIs, etc.
/// The firmware counters are always 64 bits wide.
///
/// The SBI PMU extension provides:
///
/// 1. An interface for supervisor-mode software to discover and configure per-HART hardware/firmware counters
/// 2. A typical perf compatible interface for hardware/firmware performance counters and events
/// 3. Full access to microarchitecture’s raw event encodings
///
/// To define SBI PMU extension calls, we first define important entities `counter_idx`, `event_idx`, and `event_data`.
/// The `counter_idx` is a logical number assigned to each hardware/firmware counter.
/// The `event_idx `represents a hardware (or firmware) event whereas
/// the `event_data` is 64 bits wide and represents additional configuration (or parameters) for
/// a hardware (or firmware) event.
///
/// The event_idx is a 20 bits wide number encoded as follows:
///
/// ```rust
///    event_idx[19:16] = type;
///    event_idx[15:0] = code;
/// ```
pub trait Pmu: Send {
    /// Returns the number of counters (both hardware and firmware).
    ///
    /// The value is returned in `SbiRet.value`; this call always returns SBI_SUCCESS in `SbiRet.error`.
    fn num_counters(&self) -> usize;
    /// Get details about the specified counter such as underlying CSR number, width of the counter,
    /// type of counter hardware/firmware, etc.
    ///
    /// The `counter_info` returned by this SBI call is encoded as follows:
    ///
    /// ```rust
    ///     counter_info[11:0] = CSR; // (12bit CSR number)
    ///     counter_info[17:12] = Width; // (One less than number of bits in CSR)
    ///     counter_info[XLEN-2:18] = Reserved; // Reserved for future use
    ///     counter_info[XLEN-1] = Type; // (0 = hardware and 1 = firmware)
    /// ```
    /// If `counter_info.type` == `1` then `counter_info.csr` and `counter_info.width` should be ignored.
    ///
    /// # Return value
    ///
    /// Returns the `counter_info` described above in `SbiRet.value`.
    ///
    /// The possible return error codes returned in `SbiRet.error` are shown in the table below:    
    ///
    /// | Return code             | Description
    /// |:------------------------|:----------------------------------------------
    /// | SBI_SUCCESS             | `counter_info` read successfully.
    /// | SBI_ERR_INVALID_PARAM   | `counter_idx` points to an invalid counter.
    fn counter_get_info(&self, counter_idx: usize) -> SbiRet;
    /// Find and configure a counter from a set of counters which is not started (or enabled)
    /// and can monitor the specified event.
    ///
    /// # Parameters
    ///
    /// The `counter_idx_base` and `counter_idx_mask` parameters represent the set of counters,
    /// whereas the `event_idx` represent the event to be monitored
    /// and `event_data` represents any additional event configuration.
    ///
    /// The `config_flags` parameter represent additional counter configuration and filter flags.
    /// The bit definitions of the `config_flags` parameter are shown in the table below:
    ///
    /// | Flag Name                    | Bits       | Description
    /// |:-----------------------------|:-----------|:------------
    /// | SBI_PMU_CFG_FLAG_SKIP_MATCH  | 0:0        | Skip the counter matching
    /// | SBI_PMU_CFG_FLAG_CLEAR_VALUE | 1:1        | Clear (or zero) the counter value in counter configuration
    /// | SBI_PMU_CFG_FLAG_AUTO_START  | 2:2        | Start the counter after configuring a matching counter
    /// | SBI_PMU_CFG_FLAG_SET_VUINH   | 3:3        | Event counting inhibited in VU-mode
    /// | SBI_PMU_CFG_FLAG_SET_VSINH   | 4:4        | Event counting inhibited in VS-mode
    /// | SBI_PMU_CFG_FLAG_SET_UINH    | 5:5        | Event counting inhibited in U-mode
    /// | SBI_PMU_CFG_FLAG_SET_SINH    | 6:6        | Event counting inhibited in S-mode
    /// | SBI_PMU_CFG_FLAG_SET_MINH    | 7:7        | Event counting inhibited in M-mode
    /// | *RESERVED*                   | 8:(XLEN-1) | All non-zero values are reserved for future use.
    ///
    /// *NOTE:* When *SBI_PMU_CFG_FLAG_SKIP_MATCH* is set in `config_flags`, the
    /// SBI implementation will unconditionally select the first counter from the
    /// set of counters specified by the `counter_idx_base` and `counter_idx_mask`.
    ///
    /// *NOTE:* The *SBI_PMU_CFG_FLAG_AUTO_START* flag in `config_flags` has no
    /// impact on the counter value.    
    ///
    /// *NOTE:* The `config_flags[3:7]` bits are event filtering hints so these
    /// can be ignored or overridden by the SBI implementation for security concerns
    /// or due to lack of event filtering support in the underlying RISC-V platform.
    ///
    /// # Return value
    ///
    /// Returns the `counter_idx` in `sbiret.value` upon success.
    ///
    /// In case of failure, the possible error codes returned in `sbiret.error` are shown in the table below:    
    ///
    /// | Return code           | Description
    /// |:----------------------|:----------------------------------------------
    /// | SBI_SUCCESS           | counter found and configured successfully.
    /// | SBI_ERR_INVALID_PARAM | set of counters has an invalid counter.
    /// | SBI_ERR_NOT_SUPPORTED | none of the counters can monitor specified event.
    fn counter_config_matching(
        &self,
        counter_idx_base: usize,
        counter_idx_mask: usize,
        config_flags: usize,
        event_idx: usize,
        event_data: u64,
    ) -> SbiRet;
    /// Start or enable a set of counters on the calling HART with the specified initial value.
    ///
    /// # Parameters
    ///
    /// The `counter_idx_base` and `counter_idx_mask` parameters represent the set of counters.
    /// whereas the `initial_value` parameter specifies the initial value of the counter.
    ///
    /// The bit definitions of the `start_flags` parameter are shown in the table below:
    ///
    /// | Flag Name                    | Bits       | Description
    /// |:-----------------------------|:-----------|:------------
    /// | SBI_PMU_START_SET_INIT_VALUE | 0:0        | Set the value of counters based on the `initial_value` parameter.
    /// | *RESERVED*                   | 1:(XLEN-1) | All non-zero values are reserved for future use.
    ///
    /// *NOTE*: When `SBI_PMU_START_SET_INIT_VALUE` is not set in `start_flags`, the counter value will
    /// not be modified and event counting will start from current counter value.
    ///
    /// # Return value
    ///
    /// The possible return error codes returned in `SbiRet.error` are shown in the table below:    
    ///
    /// | Return code             | Description
    /// |:------------------------|:----------------------------------------------
    /// | SBI_SUCCESS             | counter started successfully.
    /// | SBI_ERR_INVALID_PARAM   | some of the counters specified in parameters are invalid.
    /// | SBI_ERR_ALREADY_STARTED | some of the counters specified in parameters are already started.
    fn counter_start(
        &self,
        counter_idx_base: usize,
        counter_idx_mask: usize,
        start_flags: usize,
        initial_value: u64,
    ) -> SbiRet;
    /// Stop or disable a set of counters on the calling HART.
    ///
    /// # Parameters
    ///
    /// The `counter_idx_base` and `counter_idx_mask` parameters represent the set of counters.
    /// The bit definitions of the `stop_flags` parameter are shown in the table below:
    ///
    /// | Flag Name               | Bits       | Description
    /// |:------------------------|:-----------|:------------
    /// | SBI_PMU_STOP_FLAG_RESET | 0:0        | Reset the counter to event mapping.
    /// | *RESERVED*              | 1:(XLEN-1) | All non-zero values are reserved for future use.
    ///
    /// # Return value
    ///
    /// The possible return error codes returned in `SbiRet.error` are shown in the table below:    
    ///
    /// | Return code             | Description
    /// |:------------------------|:----------------------------------------------
    /// | SBI_SUCCESS             | counter stopped successfully.
    /// | SBI_ERR_INVALID_PARAM   | some of the counters specified in parameters are invalid.
    /// | SBI_ERR_ALREADY_STOPPED | some of the counters specified in parameters are already stopped.
    fn counter_stop(
        &self,
        counter_idx_base: usize,
        counter_idx_mask: usize,
        stop_flags: usize,
    ) -> SbiRet;
    /// Provide the current value of a firmware counter in `SbiRet.value`.
    ///
    /// # Parameters
    ///
    /// This function should be only used to read a firmware counter. It will return an error
    /// when user provides a hardware counter in `counter_idx` parameter.
    ///
    /// # Return value
    ///
    /// The possible return error codes returned in `SbiRet.error` are shown in the table below:    
    ///
    /// | Return code             | Description
    /// |:------------------------|:----------------------------------------------
    /// | SBI_SUCCESS             | firmware counter read successfully.
    /// | SBI_ERR_INVALID_PARAM   | `counter_idx` points to a hardware counter or an invalid counter.
    fn counter_fw_read(&self, counter_idx: usize) -> SbiRet;
}

// TODO: all the events here

static PMU: OnceFatBox<dyn Pmu + Sync + 'static> = OnceFatBox::new();

#[doc(hidden)] // use through a macro or a call from implementation
pub fn init_pmu<T: Pmu + Sync + 'static>(pmu: T) {
    let result = PMU.set(Box::new(pmu));
    if result.is_err() {
        panic!("load sbi module when already loaded")
    }
}

#[inline]
pub(crate) fn probe_pmu() -> bool {
    PMU.get().is_some()
}

#[inline]
pub(crate) fn num_counters() -> SbiRet {
    if let Some(obj) = PMU.get() {
        // Returns the number of counters (both hardware and firmware) in sbiret.value
        // and always returns SBI_SUCCESS in sbiret.error.
        return SbiRet::ok(obj.num_counters());
    }
    SbiRet::not_supported()
}

#[inline]
pub(crate) fn counter_get_info(counter_idx: usize) -> SbiRet {
    if let Some(obj) = PMU.get() {
        return obj.counter_get_info(counter_idx);
    }
    SbiRet::not_supported()
}

#[inline]
pub(crate) fn counter_config_matching(
    counter_idx_base: usize,
    counter_idx_mask: usize,
    config_flags: usize,
    event_idx: usize,
    event_data: u64,
) -> SbiRet {
    if let Some(obj) = PMU.get() {
        return obj.counter_config_matching(
            counter_idx_base,
            counter_idx_mask,
            config_flags,
            event_idx,
            event_data,
        );
    }
    SbiRet::not_supported()
}

#[inline]
pub(crate) fn counter_start(
    counter_idx_base: usize,
    counter_idx_mask: usize,
    start_flags: usize,
    initial_value: u64,
) -> SbiRet {
    if let Some(obj) = PMU.get() {
        return obj.counter_start(
            counter_idx_base,
            counter_idx_mask,
            start_flags,
            initial_value,
        );
    }
    SbiRet::not_supported()
}

#[inline]
pub(crate) fn counter_stop(
    counter_idx_base: usize,
    counter_idx_mask: usize,
    stop_flags: usize,
) -> SbiRet {
    if let Some(obj) = PMU.get() {
        return obj.counter_stop(counter_idx_base, counter_idx_mask, stop_flags);
    }
    SbiRet::not_supported()
}

#[inline]
pub(crate) fn counter_fw_read(counter_idx: usize) -> SbiRet {
    if let Some(obj) = PMU.get() {
        return obj.counter_fw_read(counter_idx);
    }
    SbiRet::not_supported()
}