1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143

use crate::{
    events::{Event, Events},
    xdr::{self, ScStatus},
    Status,
};
use backtrace::{Backtrace, BacktraceFrame};
use core::fmt::Debug;

#[derive(Clone)]
pub struct HostError {
    pub status: Status,
    pub(crate) events: Option<Events>,
    pub(crate) backtrace: backtrace::Backtrace,
}

impl std::error::Error for HostError {}

impl Debug for HostError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        // We do a little trimming here, skipping the first two frames (which
        // are always into, from, and one or more Host::err_foo calls) and all
        // the frames _after_ the short-backtrace marker that rust compiles-in.

        fn frame_name_matches(frame: &BacktraceFrame, pat: &str) -> bool {
            for sym in frame.symbols() {
                match sym.name() {
                    Some(sn) if format!("{:}", sn).contains(pat) => {
                        return true;
                    }
                    _ => (),
                }
            }
            false
        }

        fn frame_is_short_backtrace_start(frame: &BacktraceFrame) -> bool {
            frame_name_matches(frame, "__rust_begin_short_backtrace")
        }

        fn frame_is_initial_error_plumbing(frame: &BacktraceFrame) -> bool {
            frame_name_matches(frame, "::from")
                || frame_name_matches(frame, "::into")
                || frame_name_matches(frame, "Host::err")
                || frame_name_matches(frame, "::map_err")
        }

        let mut bt = self.backtrace.clone();
        bt.resolve();
        let frames: Vec<BacktraceFrame> = bt
            .frames()
            .iter()
            .skip_while(|f| frame_is_initial_error_plumbing(f))
            .take_while(|f| !frame_is_short_backtrace_start(f))
            .cloned()
            .collect();
        let bt: Backtrace = frames.into();
        writeln!(f, "HostError")?;
        writeln!(f, "Value: {:?}", self.status)?;
        // TODO: maybe make this something users can adjust?
        const MAX_DEBUG_EVENTS: usize = 10;
        match &self.events {
            None => (),
            Some(ev) => {
                let mut wrote_heading = false;
                for (i, e) in
                    ev.0.iter()
                        .rev()
                        .filter_map(|ev| match ev.event.clone() {
                            Event::Debug(e) => Some(format!("Debug {:}", e)),
                            Event::StructuredDebug(e) => Some(format!("StructuredDebug {:?}", e)),
                            _ => None,
                        })
                        .take(MAX_DEBUG_EVENTS)
                        .enumerate()
                {
                    if !wrote_heading {
                        writeln!(f)?;
                        writeln!(f, "Debug events (newest first):")?;
                        wrote_heading = true;
                    }
                    writeln!(f, "   {:?}: {:?}", i, e)?;
                }
                if ev.0.len() > MAX_DEBUG_EVENTS {
                    writeln!(f, "   {:?}: ... elided ...", MAX_DEBUG_EVENTS)?;
                }
            }
        }
        writeln!(f)?;
        writeln!(f, "Backtrace (newest first):")?;
        writeln!(f, "{:?}", bt)
    }
}

impl HostError {
    #[cfg(test)]
    pub fn result_matches_err_status<T, C>(res: Result<T, HostError>, code: C) -> bool
    where
        Status: From<C>,
    {
        match res {
            Ok(_) => false,
            Err(he) => {
                let status: Status = code.into();
                he.status == status
            }
        }
    }
}

impl<T> From<T> for HostError
where
    Status: From<T>,
{
    fn from(status: T) -> Self {
        let backtrace = backtrace::Backtrace::new_unresolved();
        let status: Status = status.into();
        let events = None;
        Self {
            status,
            events,
            backtrace,
        }
    }
}

impl std::fmt::Display for HostError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        <HostError as Debug>::fmt(self, f)
    }
}

impl TryFrom<&HostError> for ScStatus {
    type Error = xdr::Error;
    fn try_from(err: &HostError) -> Result<Self, Self::Error> {
        err.status.try_into()
    }
}

impl From<HostError> for std::io::Error {
    fn from(e: HostError) -> Self {
        std::io::Error::new(std::io::ErrorKind::Other, e)
    }
}