use crate::opcode::OpCode;

/// Specification for a single OpCode.
/// All JMP/JMP_IF_* immediate are u32 absolute offsets from function start.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct OpcodeSpec {
    pub name: &'static str,
    pub imm_bytes: u8,       // immediate payload size (decode)
    pub pops: u16,           // slots popped
    pub pushes: u16,         // slots pushed
    pub is_branch: bool,     // has a control-flow target
    pub is_terminator: bool, // ends basic block: JMP/RET/TRAP/HALT
    pub may_trap: bool,      // runtime trap possible
}

pub trait OpCodeSpecExt {
    fn spec(&self) -> OpcodeSpec;
}

impl OpCodeSpecExt for OpCode {
    fn spec(&self) -> OpcodeSpec {
        match self {
            OpCode::Nop => OpcodeSpec { name: "NOP", imm_bytes: 0, pops: 0, pushes: 0, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::Halt => OpcodeSpec { name: "HALT", imm_bytes: 0, pops: 0, pushes: 0, is_branch: false, is_terminator: true, may_trap: false },
            OpCode::Jmp => OpcodeSpec { name: "JMP", imm_bytes: 4, pops: 0, pushes: 0, is_branch: true, is_terminator: true, may_trap: false },
            OpCode::JmpIfFalse => OpcodeSpec { name: "JMP_IF_FALSE", imm_bytes: 4, pops: 1, pushes: 0, is_branch: true, is_terminator: false, may_trap: true },
            OpCode::JmpIfTrue => OpcodeSpec { name: "JMP_IF_TRUE", imm_bytes: 4, pops: 1, pushes: 0, is_branch: true, is_terminator: false, may_trap: true },
            OpCode::Trap => OpcodeSpec { name: "TRAP", imm_bytes: 0, pops: 0, pushes: 0, is_branch: false, is_terminator: true, may_trap: true },
            OpCode::PushConst => OpcodeSpec { name: "PUSH_CONST", imm_bytes: 4, pops: 0, pushes: 1, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::Pop => OpcodeSpec { name: "POP", imm_bytes: 0, pops: 1, pushes: 0, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::PopN => OpcodeSpec { name: "POP_N", imm_bytes: 4, pops: 0, pushes: 0, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::Dup => OpcodeSpec { name: "DUP", imm_bytes: 0, pops: 1, pushes: 2, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::Swap => OpcodeSpec { name: "SWAP", imm_bytes: 0, pops: 2, pushes: 2, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::PushI64 => OpcodeSpec { name: "PUSH_I64", imm_bytes: 8, pops: 0, pushes: 1, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::PushF64 => OpcodeSpec { name: "PUSH_F64", imm_bytes: 8, pops: 0, pushes: 1, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::PushBool => OpcodeSpec { name: "PUSH_BOOL", imm_bytes: 1, pops: 0, pushes: 1, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::PushI32 => OpcodeSpec { name: "PUSH_I32", imm_bytes: 4, pops: 0, pushes: 1, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::PushBounded => OpcodeSpec { name: "PUSH_BOUNDED", imm_bytes: 4, pops: 0, pushes: 1, is_branch: false, is_terminator: false, may_trap: true },
            OpCode::Add => OpcodeSpec { name: "ADD", imm_bytes: 0, pops: 2, pushes: 1, is_branch: false, is_terminator: false, may_trap: true },
            OpCode::Sub => OpcodeSpec { name: "SUB", imm_bytes: 0, pops: 2, pushes: 1, is_branch: false, is_terminator: false, may_trap: true },
            OpCode::Mul => OpcodeSpec { name: "MUL", imm_bytes: 0, pops: 2, pushes: 1, is_branch: false, is_terminator: false, may_trap: true },
            OpCode::Div => OpcodeSpec { name: "DIV", imm_bytes: 0, pops: 2, pushes: 1, is_branch: false, is_terminator: false, may_trap: true },
            OpCode::Mod => OpcodeSpec { name: "MOD", imm_bytes: 0, pops: 2, pushes: 1, is_branch: false, is_terminator: false, may_trap: true },
            OpCode::BoundToInt => OpcodeSpec { name: "BOUND_TO_INT", imm_bytes: 0, pops: 1, pushes: 1, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::IntToBoundChecked => OpcodeSpec { name: "INT_TO_BOUND_CHECKED", imm_bytes: 0, pops: 1, pushes: 1, is_branch: false, is_terminator: false, may_trap: true },
            OpCode::Eq => OpcodeSpec { name: "EQ", imm_bytes: 0, pops: 2, pushes: 1, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::Neq => OpcodeSpec { name: "NEQ", imm_bytes: 0, pops: 2, pushes: 1, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::Lt => OpcodeSpec { name: "LT", imm_bytes: 0, pops: 2, pushes: 1, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::Gt => OpcodeSpec { name: "GT", imm_bytes: 0, pops: 2, pushes: 1, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::And => OpcodeSpec { name: "AND", imm_bytes: 0, pops: 2, pushes: 1, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::Or => OpcodeSpec { name: "OR", imm_bytes: 0, pops: 2, pushes: 1, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::Not => OpcodeSpec { name: "NOT", imm_bytes: 0, pops: 1, pushes: 1, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::BitAnd => OpcodeSpec { name: "BIT_AND", imm_bytes: 0, pops: 2, pushes: 1, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::BitOr => OpcodeSpec { name: "BIT_OR", imm_bytes: 0, pops: 2, pushes: 1, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::BitXor => OpcodeSpec { name: "BIT_XOR", imm_bytes: 0, pops: 2, pushes: 1, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::Shl => OpcodeSpec { name: "SHL", imm_bytes: 0, pops: 2, pushes: 1, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::Shr => OpcodeSpec { name: "SHR", imm_bytes: 0, pops: 2, pushes: 1, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::Lte => OpcodeSpec { name: "LTE", imm_bytes: 0, pops: 2, pushes: 1, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::Gte => OpcodeSpec { name: "GTE", imm_bytes: 0, pops: 2, pushes: 1, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::Neg => OpcodeSpec { name: "NEG", imm_bytes: 0, pops: 1, pushes: 1, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::GetGlobal => OpcodeSpec { name: "GET_GLOBAL", imm_bytes: 4, pops: 0, pushes: 1, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::SetGlobal => OpcodeSpec { name: "SET_GLOBAL", imm_bytes: 4, pops: 1, pushes: 0, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::GetLocal => OpcodeSpec { name: "GET_LOCAL", imm_bytes: 4, pops: 0, pushes: 1, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::SetLocal => OpcodeSpec { name: "SET_LOCAL", imm_bytes: 4, pops: 1, pushes: 0, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::Call => OpcodeSpec { name: "CALL", imm_bytes: 4, pops: 0, pushes: 0, is_branch: false, is_terminator: false, may_trap: true },
            OpCode::Ret => OpcodeSpec { name: "RET", imm_bytes: 0, pops: 0, pushes: 0, is_branch: false, is_terminator: true, may_trap: false },
            OpCode::PushScope => OpcodeSpec { name: "PUSH_SCOPE", imm_bytes: 0, pops: 0, pushes: 0, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::PopScope => OpcodeSpec { name: "POP_SCOPE", imm_bytes: 0, pops: 0, pushes: 0, is_branch: false, is_terminator: false, may_trap: false },
            OpCode::Alloc => OpcodeSpec { name: "ALLOC", imm_bytes: 8, pops: 0, pushes: 1, is_branch: false, is_terminator: false, may_trap: true },
            OpCode::GateLoad => OpcodeSpec { name: "GATE_LOAD", imm_bytes: 4, pops: 1, pushes: 1, is_branch: false, is_terminator: false, may_trap: true },
            OpCode::GateStore => OpcodeSpec { name: "GATE_STORE", imm_bytes: 4, pops: 2, pushes: 0, is_branch: false, is_terminator: false, may_trap: true },
            OpCode::GateBeginPeek => OpcodeSpec { name: "GATE_BEGIN_PEEK", imm_bytes: 0, pops: 1, pushes: 1, is_branch: false, is_terminator: false, may_trap: true },
            OpCode::GateEndPeek => OpcodeSpec { name: "GATE_END_PEEK", imm_bytes: 0, pops: 1, pushes: 1, is_branch: false, is_terminator: false, may_trap: true },
            OpCode::GateBeginBorrow => OpcodeSpec { name: "GATE_BEGIN_BORROW", imm_bytes: 0, pops: 1, pushes: 1, is_branch: false, is_terminator: false, may_trap: true },
            OpCode::GateEndBorrow => OpcodeSpec { name: "GATE_END_BORROW", imm_bytes: 0, pops: 1, pushes: 1, is_branch: false, is_terminator: false, may_trap: true },
            OpCode::GateBeginMutate => OpcodeSpec { name: "GATE_BEGIN_MUTATE", imm_bytes: 0, pops: 1, pushes: 1, is_branch: false, is_terminator: false, may_trap: true },
            OpCode::GateEndMutate => OpcodeSpec { name: "GATE_END_MUTATE", imm_bytes: 0, pops: 1, pushes: 1, is_branch: false, is_terminator: false, may_trap: true },
            OpCode::GateRetain => OpcodeSpec { name: "GATE_RETAIN", imm_bytes: 0, pops: 1, pushes: 1, is_branch: false, is_terminator: false, may_trap: true },
            OpCode::GateRelease => OpcodeSpec { name: "GATE_RELEASE", imm_bytes: 0, pops: 1, pushes: 0, is_branch: false, is_terminator: false, may_trap: true },
            OpCode::Syscall => OpcodeSpec { name: "SYSCALL", imm_bytes: 4, pops: 0, pushes: 0, is_branch: false, is_terminator: false, may_trap: true },
            OpCode::FrameSync => OpcodeSpec { name: "FRAME_SYNC", imm_bytes: 0, pops: 0, pushes: 0, is_branch: false, is_terminator: false, may_trap: false },
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    // Infer the numeric range from the TryFrom<u16> mapping used in opcode.rs tests
    // by scanning a plausible range (0..1024) and keeping all successful decodes.
    #[test]
    fn every_opcode_has_spec_and_imm_defined() {
        let mut count = 0usize;
        for val in 0u16..=1023u16 {
            if let Ok(op) = OpCode::try_from(val) {
                let spec = op.spec();
                // Access all fields to ensure they are present and not optimized away
                let _ = (
                    spec.name,
                    spec.imm_bytes,
                    spec.pops,
                    spec.pushes,
                    spec.is_branch,
                    spec.is_terminator,
                    spec.may_trap,
                );
                // imm_bytes must be defined (0 is valid)
                assert!(spec.imm_bytes >= 0, "imm_bytes must be defined for {op:?}");
                count += 1;
            }
        }
        assert!(count > 0, "No opcodes were found via OpCode::try_from");
    }
}