use std::cell::RefCell;

use rustc_span::DUMMY_SP;

use crate::*;

/// Miri specific diagnostics
pub enum NonHaltingDiagnostic {
    PoppedTrackedPointerTag(Item),
    CreatedAlloc(AllocId),
}

/// Emit a custom diagnostic without going through the miri-engine machinery
pub fn report_diagnostic<'tcx, 'mir>(
    ecx: &InterpCx<'mir, 'tcx, Evaluator<'tcx>>,
    mut e: InterpErrorInfo<'tcx>,
) -> Option<i64> {
    use InterpError::*;
    let title = match e.kind {
        Unsupported(_) => "unsupported operation",
        UndefinedBehavior(_) => "Undefined Behavior",
        InvalidProgram(_) => bug!("This error should be impossible in Miri: {}", e),
        ResourceExhaustion(_) => "resource exhaustion",
        MachineStop(_) => "program stopped",
    };
    let msg = match e.kind {
        MachineStop(ref info) => {
            let info = info.downcast_ref::<TerminationInfo>().expect("invalid MachineStop payload");
            match info {
                TerminationInfo::Exit(code) => return Some(*code),
                TerminationInfo::Abort(None) => format!("the evaluated program aborted execution"),
                TerminationInfo::Abort(Some(msg)) => format!("the evaluated program aborted execution: {}", msg),
            }
        }
        _ => e.to_string(),
    };
    let help = match e.kind {
        Unsupported(UnsupportedOpInfo::NoMirFor(..)) =>
            Some("set `MIRI_SYSROOT` to a Miri sysroot, which you can prepare with `cargo miri setup`"),
        Unsupported(_) =>
            Some("this is likely not a bug in the program; it indicates that the program performed an operation that the interpreter does not support"),
        UndefinedBehavior(UndefinedBehaviorInfo::UbExperimental(_)) =>
            Some("this indicates a potential bug in the program: it violated *experimental* rules, and caused Undefined Behavior"),
        UndefinedBehavior(_) =>
            Some("this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior"),
        _ => None,
    };
    e.print_backtrace();
    report_msg(ecx, &format!("{}: {}", title, msg), msg, help, true)
}

/// Report an error or note (depending on the `error` argument) at the current frame's current statement.
/// Also emits a full stacktrace of the interpreter stack.
pub fn report_msg<'tcx, 'mir>(
    ecx: &InterpCx<'mir, 'tcx, Evaluator<'tcx>>,
    title: &str,
    span_msg: String,
    help: Option<&str>,
    error: bool,
) -> Option<i64> {
    let span = if let Some(frame) = ecx.stack().last() {
        frame.current_source_info().unwrap().span
    } else {
        DUMMY_SP
    };
    let mut err = if error {
        ecx.tcx.sess.struct_span_err(span, title)
    } else {
        ecx.tcx.sess.diagnostic().span_note_diag(span, title)
    };
    err.span_label(span, span_msg);
    if let Some(help) = help {
        err.help(help);
    }
    // Add backtrace
    let frames = ecx.generate_stacktrace(None);
    // We iterate with indices because we need to look at the next frame (the caller).
    for idx in 0..frames.len() {
        let frame_info = &frames[idx];
        let call_site_is_local = frames
            .get(idx + 1)
            .map_or(false, |caller_info| caller_info.instance.def_id().is_local());
        if call_site_is_local {
            err.span_note(frame_info.call_site, &frame_info.to_string());
        } else {
            err.note(&frame_info.to_string());
        }
    }

    err.emit();

    for (i, frame) in ecx.stack().iter().enumerate() {
        trace!("-------------------");
        trace!("Frame {}", i);
        trace!("    return: {:?}", frame.return_place.map(|p| *p));
        for (i, local) in frame.locals.iter().enumerate() {
            trace!("    local {}: {:?}", i, local.value);
        }
    }
    // Let the reported error determine the return code.
    return None;
}

thread_local! {
    static DIAGNOSTICS: RefCell<Vec<NonHaltingDiagnostic>> = RefCell::new(Vec::new());
}

/// Schedule a diagnostic for emitting. This function works even if you have no `InterpCx` available.
/// The diagnostic will be emitted after the current interpreter step is finished.
pub fn register_diagnostic(e: NonHaltingDiagnostic) {
    DIAGNOSTICS.with(|diagnostics| diagnostics.borrow_mut().push(e));
}

impl<'mir, 'tcx> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {}
pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx> {
    /// Emit all diagnostics that were registed with `register_diagnostics`
    fn process_diagnostics(&self) {
        let this = self.eval_context_ref();
        DIAGNOSTICS.with(|diagnostics| {
            for e in diagnostics.borrow_mut().drain(..) {
                use NonHaltingDiagnostic::*;
                let msg = match e {
                    PoppedTrackedPointerTag(item) =>
                        format!("popped tracked tag for item {:?}", item),
                    CreatedAlloc(AllocId(id)) =>
                        format!("created allocation with id {}", id),
                };
                report_msg(this, "tracking was triggered", msg, None, false);
            }
        });
    }
}