Move trace_error() functionality from libimagutil to libimagerror

3 files changed, 82 insertions, 0 deletions

diff --git a/libimagerror/Cargo.toml b/libimagerror/Cargo.toml
index bd769698..2227ce9e 100644
--- a/libimagerror/Cargo.toml
+++ b/libimagerror/Cargo.toml
@@ -4,3 +4,5 @@ version = "0.1.0"
 authors = ["Matthias Beyer <mail@beyermatthias.de>"]
 
 [dependencies]
+log = "0.3"
+ansi_term = "0.7"
diff --git a/libimagerror/src/lib.rs b/libimagerror/src/lib.rs
index 9f79f549..d7f374a7 100644
--- a/libimagerror/src/lib.rs
+++ b/libimagerror/src/lib.rs
@@ -1 +1,5 @@
+#[macro_use] extern crate log;
+extern crate ansi_term;
+
 pub mod error_gen;
+pub mod trace;
diff --git a/libimagerror/src/trace.rs b/libimagerror/src/trace.rs
new file mode 100644
index 00000000..e04b292f
--- /dev/null
+++ b/libimagerror/src/trace.rs
@@ -0,0 +1,76 @@
+use std::error::Error;
+use std::io::Write;
+use std::io::stderr;
+
+use ansi_term::Colour::Red;
+
+/// Print an Error type and its cause recursively
+///
+/// The error is printed with "Error NNNN :" as prefix, where "NNNN" is a number which increases
+/// which each recursion into the errors cause. The error description is used to visualize what
+/// failed and if there is a cause "-- caused by:" is appended, and the cause is printed on the next
+/// line.
+///
+/// Example output:
+///
+/// ```ignore
+/// Error    1 : Some error -- caused by:
+/// Error    2 : Some other error -- caused by:
+/// Error    3 : Yet another Error -- caused by:
+/// ...
+///
+/// Error <NNNN> : <Error description>
+/// ```
+pub fn trace_error(e: &Error) {
+    print_trace_maxdepth(count_error_causes(e), e, ::std::u64::MAX);
+    write!(stderr(), "\n").ok();
+}
+
+/// Print an Error type and its cause recursively, but only `max` levels
+///
+/// Output is the same as for `trace_error()`, though there are only `max` levels printed.
+pub fn trace_error_maxdepth(e: &Error, max: u64) {
+    let n = count_error_causes(e);
+    let msg = Red.blink().paint(format!("{}/{} Levels of errors will be printed\n",
+                                        (if max > n { n } else { max }), n));
+    write!(stderr(), "{}", msg).ok();
+    print_trace_maxdepth(n, e, max);
+    write!(stderr(), "").ok();
+}
+
+/// Print an Error type and its cause recursively with the debug!() macro
+///
+/// Output is the same as for `trace_error()`.
+pub fn trace_error_dbg(e: &Error) {
+    print_trace_dbg(0, e);
+}
+
+/// Helper function for `trace_error()` and `trace_error_maxdepth()`.
+///
+/// Returns the cause of the last processed error in the recursion, so `None` if all errors where
+/// processed.
+fn print_trace_maxdepth(idx: u64, e: &Error, max: u64) -> Option<&Error> {
+    if e.cause().is_some() && idx > 0 {
+        match print_trace_maxdepth(idx - 1, e.cause().unwrap(), max) {
+            None    => write!(stderr(), "\n").ok(),
+            Some(_) => write!(stderr(), " -- caused:\n").ok(),
+        };
+    } else {
+        write!(stderr(), "\n").ok();
+    }
+    write!(stderr(), "{}: {}", Red.paint(format!("ERROR[{:>4}]", idx)), e.description()).ok();
+    e.cause()
+}
+
+/// Count errors in `Error::cause()` recursively
+fn count_error_causes(e: &Error) -> u64 {
+    1 + if e.cause().is_some() { count_error_causes(e.cause().unwrap()) } else { 0 }
+}
+
+fn print_trace_dbg(idx: u64, e: &Error) {
+    debug!("{}: {}", Red.blink().paint(format!("ERROR[{:>4}]", idx)), e.description());
+    if e.cause().is_some() {
+        print_trace_dbg(idx + 1, e.cause().unwrap());
+    }
+}
+