//! Narrow MAVLink arm/disarm command decoding.
//!
//! This module deliberately accepts no actuator-value or motor-test command.
//! A board must pass accepted requests to its single actuator-state owner; this
//! decoder has no access to output hardware.

use mavlink::Message;

use crate::{MavlinkFrame, message};

/// A requested change to the vehicle's arming state.
#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum ArmRequest {
    /// Request the armed-idle state.
    Arm,
    /// Request electrically inactive outputs.
    Disarm,
}

/// Decodes a targeted MAVLink `MAV_CMD_COMPONENT_ARM_DISARM` command.
///
/// Only `param1` values exactly equal to `0.0` (disarm) or `1.0` (arm) are
/// accepted. Broadcast targets are intentionally rejected: an actuator command
/// must name this vehicle and its component explicitly.
pub fn decode_arm_request(
    frame: &MavlinkFrame,
    system_id: u8,
    component_id: u8,
) -> Option<ArmRequest> {
    let message = message::MavMessage::parse(
        mavlink::MavlinkVersion::V2,
        frame.message_id(),
        frame.payload(),
    )
    .ok()?;

    let message::MavMessage::COMMAND_LONG(command) = message else {
        return None;
    };
    if command.command != message::MavCmd::MAV_CMD_COMPONENT_ARM_DISARM
        || command.target_system != system_id
        || command.target_component != component_id
    {
        return None;
    }

    match command.param1 {
        0.0 => Some(ArmRequest::Disarm),
        1.0 => Some(ArmRequest::Arm),
        _ => None,
    }
}

#[cfg(test)]
mod tests {
    use super::{ArmRequest, decode_arm_request};
    use crate::{MavlinkFrame, message};

    fn command(target_system: u8, target_component: u8, value: f32) -> MavlinkFrame {
        let mut frame = MavlinkFrame::new();
        frame.serialize_message_data(
            message::MavHeader {
                sequence: 0,
                system_id: 42,
                component_id: 7,
            },
            &message::COMMAND_LONG_DATA {
                param1: value,
                param2: 0.0,
                param3: 0.0,
                param4: 0.0,
                param5: 0.0,
                param6: 0.0,
                param7: 0.0,
                command: message::MavCmd::MAV_CMD_COMPONENT_ARM_DISARM,
                target_system,
                target_component,
                confirmation: 0,
            },
        );
        frame
    }

    #[test]
    fn accepts_explicit_targeted_arm_and_disarm() {
        assert_eq!(
            decode_arm_request(&command(1, 1, 1.0), 1, 1),
            Some(ArmRequest::Arm)
        );
        assert_eq!(
            decode_arm_request(&command(1, 1, 0.0), 1, 1),
            Some(ArmRequest::Disarm)
        );
    }

    #[test]
    fn rejects_broadcast_wrong_target_and_invalid_parameter() {
        assert_eq!(decode_arm_request(&command(0, 0, 1.0), 1, 1), None);
        assert_eq!(decode_arm_request(&command(2, 1, 1.0), 1, 1), None);
        assert_eq!(decode_arm_request(&command(1, 1, 0.5), 1, 1), None);
    }
}