lift-export 0.4.0

use lift_core::context::Context;
use lift_quantum::gates::QuantumGate;
use std::fmt::Write;
use thiserror::Error;

#[derive(Debug, Error)]
pub enum QasmExportError {
    #[error("Unsupported gate for QASM export: {0}")]
    UnsupportedGate(String),
    #[error("Export error: {0}")]
    General(String),
}

#[derive(Debug)]
pub struct QasmExporter;

impl QasmExporter {
    pub fn new() -> Self {
        Self
    }

    pub fn export(&self, ctx: &Context) -> Result<String, QasmExportError> {
        let mut output = String::new();

        let _ = writeln!(output, "OPENQASM 3.0;");
        let _ = writeln!(output, "// Generated by LIFT framework");
        let _ = writeln!(output);

        // Count qubits needed
        let mut max_qubits = 0usize;
        for (_val_key, val) in &ctx.values {
            if ctx.is_qubit_type(val.ty) {
                max_qubits += 1;
            }
        }

        // Estimate unique qubits from block args
        let mut qubit_args = 0;
        for (_block_key, block) in &ctx.blocks {
            for &arg in &block.args {
                if let Some(val) = ctx.get_value(arg) {
                    if ctx.is_qubit_type(val.ty) {
                        qubit_args += 1;
                    }
                }
            }
        }
        let num_qubits = if qubit_args > 0 {
            qubit_args
        } else {
            max_qubits.max(1)
        };

        let _ = writeln!(output, "qubit[{}] q;", num_qubits);
        let _ = writeln!(output, "bit[{}] c;", num_qubits);
        let _ = writeln!(output);

        // Export gate operations
        let mut qubit_counter = 0usize;
        for (_op_key, op) in &ctx.ops {
            let op_name = ctx.strings.resolve(op.name).to_string();

            if let Some(gate) = QuantumGate::from_name(&op_name) {
                let q0 = qubit_counter % num_qubits;
                let q1 = (qubit_counter + 1) % num_qubits;
                let q2 = (qubit_counter + 2) % num_qubits;
                let angle = op.attrs.get_float("angle").unwrap_or(0.0);
                let theta = op.attrs.get_float("theta").unwrap_or(0.0);
                let phi = op.attrs.get_float("phi").unwrap_or(0.0);
                let lambda = op.attrs.get_float("lambda").unwrap_or(0.0);

                match gate {
                    // 1-qubit standard
                    QuantumGate::H => {
                        let _ = writeln!(output, "h q[{}];", q0);
                    }
                    QuantumGate::X => {
                        let _ = writeln!(output, "x q[{}];", q0);
                    }
                    QuantumGate::Y => {
                        let _ = writeln!(output, "y q[{}];", q0);
                    }
                    QuantumGate::Z => {
                        let _ = writeln!(output, "z q[{}];", q0);
                    }
                    QuantumGate::S => {
                        let _ = writeln!(output, "s q[{}];", q0);
                    }
                    QuantumGate::Sdg => {
                        let _ = writeln!(output, "sdg q[{}];", q0);
                    }
                    QuantumGate::T => {
                        let _ = writeln!(output, "t q[{}];", q0);
                    }
                    QuantumGate::Tdg => {
                        let _ = writeln!(output, "tdg q[{}];", q0);
                    }
                    QuantumGate::SX => {
                        let _ = writeln!(output, "sx q[{}];", q0);
                    }
                    // 1-qubit parametric
                    QuantumGate::RX => {
                        let _ = writeln!(output, "rx({}) q[{}];", angle, q0);
                    }
                    QuantumGate::RY => {
                        let _ = writeln!(output, "ry({}) q[{}];", angle, q0);
                    }
                    QuantumGate::RZ => {
                        let _ = writeln!(output, "rz({}) q[{}];", angle, q0);
                    }
                    QuantumGate::P => {
                        let _ = writeln!(output, "p({}) q[{}];", angle, q0);
                    }
                    QuantumGate::U1 => {
                        let _ = writeln!(output, "u1({}) q[{}];", lambda, q0);
                    }
                    QuantumGate::U2 => {
                        let _ = writeln!(output, "u2({}, {}) q[{}];", phi, lambda, q0);
                    }
                    QuantumGate::U3 => {
                        let _ = writeln!(output, "u3({}, {}, {}) q[{}];", theta, phi, lambda, q0);
                    }
                    // 1-qubit fixed-angle
                    QuantumGate::Rx90 => {
                        let _ = writeln!(output, "rx(pi/2) q[{}];", q0);
                    }
                    QuantumGate::Rx180 => {
                        let _ = writeln!(output, "rx(pi) q[{}];", q0);
                    }
                    // 1-qubit special
                    QuantumGate::VirtualRZ => {
                        let _ = writeln!(output, "rz({}) q[{}]; // virtual", angle, q0);
                    }
                    QuantumGate::GlobalPhase => {
                        let _ = writeln!(output, "gphase({});", angle);
                    }
                    // 2-qubit standard
                    QuantumGate::CX => {
                        let _ = writeln!(output, "cx q[{}], q[{}];", q0, q1);
                    }
                    QuantumGate::CZ => {
                        let _ = writeln!(output, "cz q[{}], q[{}];", q0, q1);
                    }
                    QuantumGate::CY => {
                        let _ = writeln!(output, "cy q[{}], q[{}];", q0, q1);
                    }
                    QuantumGate::SWAP => {
                        let _ = writeln!(output, "swap q[{}], q[{}];", q0, q1);
                    }
                    QuantumGate::ISWAP => {
                        let _ = writeln!(output, "iswap q[{}], q[{}];", q0, q1);
                    }
                    QuantumGate::ECR => {
                        let _ = writeln!(output, "ecr q[{}], q[{}];", q0, q1);
                    }
                    QuantumGate::RZX => {
                        let _ = writeln!(output, "rzx({}) q[{}], q[{}];", angle, q0, q1);
                    }
                    // 2-qubit parametric
                    QuantumGate::CP => {
                        let _ = writeln!(output, "cp({}) q[{}], q[{}];", angle, q0, q1);
                    }
                    QuantumGate::CPhase => {
                        let _ = writeln!(output, "cphase({}) q[{}], q[{}];", angle, q0, q1);
                    }
                    QuantumGate::XX => {
                        let _ = writeln!(output, "rxx({}) q[{}], q[{}];", angle, q0, q1);
                    }
                    QuantumGate::YY => {
                        let _ = writeln!(output, "ryy({}) q[{}], q[{}];", angle, q0, q1);
                    }
                    QuantumGate::ZZ => {
                        let _ = writeln!(output, "rzz({}) q[{}], q[{}];", angle, q0, q1);
                    }
                    QuantumGate::XY => {
                        let _ = writeln!(output, "xy({}) q[{}], q[{}];", angle, q0, q1);
                    }
                    QuantumGate::MS => {
                        let _ = writeln!(output, "ms q[{}], q[{}];", q0, q1);
                    }
                    // 3-qubit
                    QuantumGate::CCX => {
                        let _ = writeln!(output, "ccx q[{}], q[{}], q[{}];", q0, q1, q2);
                    }
                    QuantumGate::CSWAP => {
                        let _ = writeln!(output, "cswap q[{}], q[{}], q[{}];", q0, q1, q2);
                    }
                    // Multi-controlled
                    QuantumGate::MCX => {
                        let _ = writeln!(output, "mcx q[{}], q[{}], q[{}];", q0, q1, q2);
                    }
                    QuantumGate::MCZ => {
                        let _ = writeln!(output, "mcz q[{}], q[{}], q[{}];", q0, q1, q2);
                    }
                    // Measurement and control
                    QuantumGate::Measure => {
                        let _ = writeln!(output, "c[{}] = measure q[{}];", q0, q0);
                    }
                    QuantumGate::MeasureAll => {
                        for i in 0..num_qubits {
                            let _ = writeln!(output, "c[{}] = measure q[{}];", i, i);
                        }
                    }
                    QuantumGate::Reset => {
                        let _ = writeln!(output, "reset q[{}];", q0);
                    }
                    QuantumGate::Barrier => {
                        let _ = writeln!(output, "barrier q;");
                    }
                    QuantumGate::Init => {
                        let _ = writeln!(output, "reset q[{}];", q0);
                    }
                    QuantumGate::Delay => {
                        let _ = writeln!(output, "delay[100ns] q[{}];", q0);
                    }
                    // IonQ native
                    QuantumGate::GPI => {
                        let _ = writeln!(output, "gpi({}) q[{}];", angle, q0);
                    }
                    QuantumGate::GPI2 => {
                        let _ = writeln!(output, "gpi2({}) q[{}];", angle, q0);
                    }
                    // Control flow and generic
                    QuantumGate::IfElse => {
                        let _ = writeln!(output, "// if-else control flow");
                    }
                    QuantumGate::ParamGate => {
                        let _ = writeln!(output, "// parameterised gate: {}", op_name);
                    }
                }
                qubit_counter += 1;
            }
        }

        Ok(output)
    }
}

impl Default for QasmExporter {
    fn default() -> Self {
        Self::new()
    }
}