use std::fs;
use std::io::Write;
use std::path::{Path, PathBuf};
use std::process::Command;

pub struct Opts {
    pub out: Option<PathBuf>,
    pub nyrt: Option<PathBuf>,
    pub opt_level: Option<String>,
    pub timeout_ms: Option<u64>,
}

fn resolve_ny_llvmc() -> PathBuf {
    if let Ok(s) = std::env::var("NYASH_NY_LLVM_COMPILER") {
        if !s.is_empty() { return PathBuf::from(s); }
    }
    if let Ok(p) = which::which("ny-llvmc") { return p; }
    PathBuf::from("target/release/ny-llvmc")
}

/// Compile MIR(JSON v0) to an object file (.o) using ny-llvmc. Returns the output path.
/// Fail‑Fast: prints stable tags and returns Err with the same message.
pub fn mir_json_to_object(mir_json: &str, opts: Opts) -> Result<PathBuf, String> {
    // Optional provider selection (default: ny-llvmc)
    match std::env::var("HAKO_LLVM_EMIT_PROVIDER").ok().as_deref() {
        Some("llvmlite") => return mir_json_to_object_llvmlite(mir_json, &opts),
        _ => {}
    }
    // Basic shape check for MIR(JSON v0)
    if !mir_json.contains("\"functions\"") || !mir_json.contains("\"blocks\"") {
        let tag = "[llvmemit/input/invalid] missing functions/blocks keys";
        eprintln!("{}", tag);
        return Err(tag.into());
    }

    let ny_llvmc = resolve_ny_llvmc();
    if !ny_llvmc.exists() {
        let tag = format!("[llvmemit/ny-llvmc/not-found] path={}", ny_llvmc.display());
        eprintln!("{}", tag);
        return Err(tag);
    }

    // Write MIR JSON to temp
    let tmp_dir = std::env::temp_dir();
    let in_path = tmp_dir.join("hako_llvm_in.json");
    {
        let mut f = fs::File::create(&in_path).map_err(|e| format!("[llvmemit/tmp/write-failed] {}", e))?;
        f.write_all(mir_json.as_bytes()).map_err(|e| format!("[llvmemit/tmp/write-failed] {}", e))?;
    }

    // Output path
    let out_path = if let Some(p) = opts.out.clone() { p } else { tmp_dir.join("hako_llvm_out.o") };
    if let Some(parent) = out_path.parent() { let _ = fs::create_dir_all(parent); }

    // Build command: ny-llvmc --in <json> --emit obj --out <out>
    let mut cmd = Command::new(&ny_llvmc);
    cmd.arg("--in").arg(&in_path)
        .arg("--emit").arg("obj")
        .arg("--out").arg(&out_path);
    if let Some(nyrt) = opts.nyrt.as_ref() { cmd.arg("--nyrt").arg(nyrt); }
    if let Some(level) = opts.opt_level.as_ref() {
        cmd.env("HAKO_LLVM_OPT_LEVEL", level);
        cmd.env("NYASH_LLVM_OPT_LEVEL", level);
    }

    let status = cmd.status().map_err(|e| format!("[llvmemit/spawn/error] {}", e))?;
    if !status.success() {
        let code = status.code().unwrap_or(1);
        let tag = format!("[llvmemit/ny-llvmc/failed status={}]", code);
        eprintln!("{}", tag);
        return Err(tag);
    }
    if !out_path.exists() {
        let tag = format!("[llvmemit/output/missing] {}", out_path.display());
        eprintln!("{}", tag);
        return Err(tag);
    }
    Ok(out_path)
}

fn resolve_python3() -> Option<PathBuf> {
    if let Ok(p) = which::which("python3") { return Some(p); }
    if let Ok(p) = which::which("python") { return Some(p); }
    None
}

fn resolve_llvmlite_harness() -> Option<PathBuf> {
    if let Ok(root) = std::env::var("NYASH_ROOT") {
        let p = PathBuf::from(root).join("tools/llvmlite_harness.py");
        if p.exists() { return Some(p); }
    }
    let p = PathBuf::from("tools/llvmlite_harness.py");
    if p.exists() { return Some(p); }
    // Also try repo-relative (target may run elsewhere)
    let p2 = PathBuf::from("../tools/llvmlite_harness.py");
    if p2.exists() { return Some(p2); }
    None
}

/// Compile via llvmlite harness (opt-in provider). Returns output path or tagged error.
fn mir_json_to_object_llvmlite(mir_json: &str, opts: &Opts) -> Result<PathBuf, String> {
    if !mir_json.contains("\"functions\"") || !mir_json.contains("\"blocks\"") {
        let tag = "[llvmemit/input/invalid] missing functions/blocks keys";
        eprintln!("{}", tag);
        return Err(tag.into());
    }
    let py = resolve_python3().ok_or_else(|| {
        let tag = String::from("[llvmemit/llvmlite/python-not-found]");
        eprintln!("{}", tag);
        tag
    })?;
    let harness = resolve_llvmlite_harness().ok_or_else(|| {
        let tag = String::from("[llvmemit/llvmlite/harness-not-found] tools/llvmlite_harness.py");
        eprintln!("{}", tag);
        tag
    })?;

    // Write MIR JSON to temp
    let tmp_dir = std::env::temp_dir();
    let in_path = tmp_dir.join("hako_llvm_in.json");
    {
        let mut f = fs::File::create(&in_path).map_err(|e| format!("[llvmemit/tmp/write-failed] {}", e))?;
        f.write_all(mir_json.as_bytes()).map_err(|e| format!("[llvmemit/tmp/write-failed] {}", e))?;
    }
    let out_path = if let Some(p) = opts.out.clone() { p } else { tmp_dir.join("hako_llvm_out.o") };
    if let Some(parent) = out_path.parent() { let _ = fs::create_dir_all(parent); }

    // Run: python3 tools/llvmlite_harness.py --in <json> --out <out>
    let status = Command::new(&py)
        .arg(&harness)
        .arg("--in").arg(&in_path)
        .arg("--out").arg(&out_path)
        .status()
        .map_err(|e| format!("[llvmemit/llvmlite/spawn/error] {}", e))?;
    if !status.success() {
        let code = status.code().unwrap_or(1);
        let tag = format!("[llvmemit/llvmlite/failed status={}]", code);
        eprintln!("{}", tag);
        return Err(tag);
    }
    if !out_path.exists() {
        let tag = format!("[llvmemit/output/missing] {}", out_path.display());
        eprintln!("{}", tag);
        return Err(tag);
    }
    Ok(out_path)
}