use anyhow::Result;
use prometeu_bytecode::assembler::assemble;
use prometeu_bytecode::model::{
    BytecodeModule, ConstantPoolEntry, DebugInfo, Export, FunctionMeta, SyscallDecl,
};
use std::fs;
use std::path::PathBuf;

fn asm(s: &str) -> Vec<u8> {
    assemble(s).expect("assemble")
}

pub fn generate() -> Result<()> {
    let mut rom: Vec<u8> = Vec::new();
    let syscalls = vec![
        SyscallDecl {
            module: "gfx".into(),
            name: "clear_565".into(),
            version: 1,
            arg_slots: 1,
            ret_slots: 0,
        },
        SyscallDecl {
            module: "gfx".into(),
            name: "draw_disc".into(),
            version: 1,
            arg_slots: 5,
            ret_slots: 0,
        },
        SyscallDecl {
            module: "gfx".into(),
            name: "draw_text".into(),
            version: 1,
            arg_slots: 4,
            ret_slots: 0,
        },
        SyscallDecl {
            module: "log".into(),
            name: "write".into(),
            version: 1,
            arg_slots: 2,
            ret_slots: 0,
        },
        SyscallDecl {
            module: "gfx".into(),
            name: "set_sprite".into(),
            version: 1,
            arg_slots: 10,
            ret_slots: 1,
        },
    ];

    heavy_load(&mut rom);
    // light_load(&mut rom);

    let functions = vec![FunctionMeta {
        code_offset: 0,
        code_len: rom.len() as u32,
        param_slots: 0,
        local_slots: 2,
        return_slots: 0,
        max_stack_slots: 16,
    }];

    let module = BytecodeModule {
        version: 0,
        const_pool: vec![
            ConstantPoolEntry::String("stress".into()),
            ConstantPoolEntry::String("frame".into()),
            ConstantPoolEntry::String("missing_glyph_bank".into()),
        ],
        functions,
        code: rom,
        debug_info: Some(DebugInfo {
            pc_to_span: vec![],
            function_names: vec![(0, "main".into())],
        }),
        exports: vec![Export { symbol: "main".into(), func_idx: 0 }],
        syscalls,
    };

    let bytes = module.serialize();

    let mut out_dir = PathBuf::from(env!("CARGO_MANIFEST_DIR"));
    out_dir.pop(); // pbxgen-stress
    out_dir.pop(); // tools
    out_dir.pop(); // crates
    out_dir.push("test-cartridges");
    out_dir.push("stress-console");
    fs::create_dir_all(&out_dir)?;
    fs::write(out_dir.join("program.pbx"), bytes)?;
    let assets_pa_path = out_dir.join("assets.pa");
    if assets_pa_path.exists() {
        fs::remove_file(&assets_pa_path)?;
    }
    fs::write(out_dir.join("manifest.json"), b"{\n  \"magic\": \"PMTU\",\n  \"cartridge_version\": 1,\n  \"app_id\": 1,\n  \"title\": \"Stress Console\",\n  \"app_version\": \"0.1.0\",\n  \"app_mode\": \"Game\",\n  \"capabilities\": [\"gfx\", \"log\"]\n}\n")?;
    Ok(())
}

#[allow(dead_code)]
fn heavy_load(rom: &mut Vec<u8>) {
    // Single function 0: main
    // Everything runs here — no coroutines, no SPAWN, no YIELD.
    //
    // Global 0 = t (frame counter)
    // Local 0 = scratch
    // Local 1 = loop counter for discs
    //
    // Loop:
    //   t = (t + 1)
    //   clear screen
    //   draw 500 discs using t for animation
    //   draw 20 texts using t for animation
    //   RET (runtime handles the frame loop)

    // --- init locals ---
    // local 0: scratch
    // local 1: loop counter for discs
    rom.extend(asm("PUSH_I32 0\nSET_LOCAL 0\nPUSH_I32 0\nSET_LOCAL 1"));

    // --- t = (t + 1) ---
    // t is global 0 to persist across prepare_call resets
    rom.extend(asm("GET_GLOBAL 0\nPUSH_I32 1\nADD\nSET_GLOBAL 0"));

    // --- clear screen ---
    rom.extend(asm("PUSH_I32 0\nHOSTCALL 0"));
    // --- call status-first syscall path once per frame and drop status ---
    rom.extend(asm(
        "PUSH_I32 0\nPUSH_I32 0\nPUSH_I32 0\nPUSH_I32 0\nPUSH_I32 0\nPUSH_I32 0\nPUSH_BOOL 0\nPUSH_BOOL 0\nPUSH_BOOL 0\nPUSH_I32 0\nHOSTCALL 4\nPOP_N 1",
    ));

    // --- draw 500 discs ---
    rom.extend(asm("PUSH_I32 0\nSET_LOCAL 1"));
    let disc_loop_start = rom.len() as u32;
    rom.extend(asm("GET_LOCAL 1\nPUSH_I32 500\nLT"));
    let jif_disc_end_offset = rom.len() + 2;
    rom.extend(asm("JMP_IF_FALSE 0"));

    // x = (t * (i+7) + i * 13) % 320
    rom.extend(asm("GET_GLOBAL 0\nGET_LOCAL 1\nPUSH_I32 7\nADD\nMUL\nGET_LOCAL 1\nPUSH_I32 13\nMUL\nADD\nPUSH_I32 320\nMOD"));
    // y = (t * (i+11) + i * 17) % 180
    rom.extend(asm("GET_GLOBAL 0\nGET_LOCAL 1\nPUSH_I32 11\nADD\nMUL\nGET_LOCAL 1\nPUSH_I32 17\nMUL\nADD\nPUSH_I32 180\nMOD"));
    // r = ( (i*13) % 20 ) + 5
    rom.extend(asm("GET_LOCAL 1\nPUSH_I32 13\nMUL\nPUSH_I32 20\nMOD\nPUSH_I32 5\nADD"));
    // border color = (i * 1234) & 0xFFFF
    rom.extend(asm("GET_LOCAL 1\nPUSH_I32 1234\nMUL\nPUSH_I32 65535\nBIT_AND"));
    // fill color = (i * 5678 + t) & 0xFFFF
    rom.extend(asm("GET_LOCAL 1\nPUSH_I32 5678\nMUL\nGET_GLOBAL 0\nADD\nPUSH_I32 65535\nBIT_AND"));
    // HOSTCALL gfx.draw_disc (x, y, r, border, fill)
    rom.extend(asm("HOSTCALL 1"));

    // i++
    rom.extend(asm("GET_LOCAL 1\nPUSH_I32 1\nADD\nSET_LOCAL 1"));
    let jmp_disc_loop_offset = rom.len() + 2;
    rom.extend(asm("JMP 0"));
    let disc_loop_end = rom.len() as u32;

    // --- draw 20 texts ---
    rom.extend(asm("PUSH_I32 0\nSET_LOCAL 1"));
    let text_loop_start = rom.len() as u32;
    rom.extend(asm("GET_LOCAL 1\nPUSH_I32 20\nLT"));
    let jif_text_end_offset = rom.len() + 2;
    rom.extend(asm("JMP_IF_FALSE 0"));

    // x = (t * 3 + i * 40) % 320
    rom.extend(asm(
        "GET_GLOBAL 0\nPUSH_I32 3\nMUL\nGET_LOCAL 1\nPUSH_I32 40\nMUL\nADD\nPUSH_I32 320\nMOD",
    ));
    // y = (i * 30 + t) % 180
    rom.extend(asm("GET_LOCAL 1\nPUSH_I32 30\nMUL\nGET_GLOBAL 0\nADD\nPUSH_I32 180\nMOD"));
    // string (toggle between "stress" and "frame")
    rom.extend(asm("GET_LOCAL 1\nPUSH_I32 1\nBIT_AND\nPUSH_I32 0\nNEQ"));
    let jif_text_alt_offset = rom.len() + 2;
    rom.extend(asm("JMP_IF_FALSE 0"));
    rom.extend(asm("PUSH_CONST 0")); // "stress"
    let jmp_text_join_offset = rom.len() + 2;
    rom.extend(asm("JMP 0"));
    let text_alt_target = rom.len() as u32;
    rom.extend(asm("PUSH_CONST 1")); // "frame"
    let text_join_target = rom.len() as u32;

    // color = (t * 10 + i * 1000) & 0xFFFF
    rom.extend(asm("GET_GLOBAL 0\nPUSH_I32 10\nMUL\nGET_LOCAL 1\nPUSH_I32 1000\nMUL\nADD\nPUSH_I32 65535\nBIT_AND"));
    // HOSTCALL gfx.draw_text (x, y, str, color)
    rom.extend(asm("HOSTCALL 2"));

    // i++
    rom.extend(asm("GET_LOCAL 1\nPUSH_I32 1\nADD\nSET_LOCAL 1"));
    let jmp_text_loop_offset = rom.len() + 2;
    rom.extend(asm("JMP 0"));
    let text_loop_end = rom.len() as u32;

    // --- log every 60 frames ---
    rom.extend(asm("GET_GLOBAL 0\nPUSH_I32 60\nMOD\nPUSH_I32 0\nEQ"));
    let jif_log_offset = rom.len() + 2;
    rom.extend(asm("JMP_IF_FALSE 0"));
    rom.extend(asm("PUSH_I32 2\nPUSH_CONST 0\nHOSTCALL 3"));
    let after_log = rom.len() as u32;

    // --- end of function ---
    rom.extend(asm("FRAME_SYNC\nRET"));

    // --- Patch jump targets ---
    let patch = |buf: &mut Vec<u8>, imm_offset: usize, target: u32| {
        buf[imm_offset..imm_offset + 4].copy_from_slice(&target.to_le_bytes());
    };

    patch(rom, jif_disc_end_offset, disc_loop_end);
    patch(rom, jmp_disc_loop_offset, disc_loop_start);

    patch(rom, jif_text_end_offset, text_loop_end);
    patch(rom, jif_text_alt_offset, text_alt_target);
    patch(rom, jmp_text_join_offset, text_join_target);
    patch(rom, jmp_text_loop_offset, text_loop_start);

    patch(rom, jif_log_offset, after_log);
}