//! Configuration options for customizing the behavior of the provided panic
//! and error reporting hooks
use crate::{
    section::PanicMessage,
    writers::{EnvSection, WriterExt},
};
use fmt::Display;
use indenter::{indented, Format};
use owo_colors::OwoColorize;
use std::env;
use std::fmt::Write as _;
use std::{fmt, path::PathBuf, sync::Arc};

#[derive(Debug)]
struct InstallError;

impl fmt::Display for InstallError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.write_str("could not install the BacktracePrinter as another was already installed")
    }
}

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

/// A representation of a Frame from a Backtrace or a SpanTrace
#[derive(Debug)]
#[non_exhaustive]
pub struct Frame {
    /// Frame index
    pub n: usize,
    /// frame symbol name
    pub name: Option<String>,
    /// source line number
    pub lineno: Option<u32>,
    /// source file path
    pub filename: Option<PathBuf>,
}

impl fmt::Display for Frame {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let is_dependency_code = self.is_dependency_code();

        // Print frame index.
        write!(f, "{:>2}: ", self.n)?;

        // Does the function have a hash suffix?
        // (dodging a dep on the regex crate here)
        let name = self.name.as_deref().unwrap_or("<unknown>");
        let has_hash_suffix = name.len() > 19
            && &name[name.len() - 19..name.len() - 16] == "::h"
            && name[name.len() - 16..].chars().all(|x| x.is_digit(16));

        // Print function name.

        if has_hash_suffix {
            if is_dependency_code {
                write!(f, "{}", (&name[..name.len() - 19]).green())?;
            } else {
                write!(f, "{}", (&name[..name.len() - 19]).bright_red())?;
            }
            write!(f, "{}", (&name[name.len() - 19..]).bright_black())?;
        } else {
            write!(f, "{}", name)?;
        }

        let mut separated = f.header("\n");

        // Print source location, if known.
        if let Some(ref file) = self.filename {
            let filestr = file.to_str().unwrap_or("<bad utf8>");
            let lineno = self
                .lineno
                .map_or("<unknown line>".to_owned(), |x| x.to_string());
            write!(
                &mut separated.ready(),
                "    at {}:{}",
                filestr.purple(),
                lineno.purple()
            )?;
        } else {
            write!(&mut separated.ready(), "    at <unknown source file>")?;
        }

        let v = if std::thread::panicking() {
            panic_verbosity()
        } else {
            lib_verbosity()
        };

        // Maybe print source.
        if v >= Verbosity::Full {
            write!(&mut separated.ready(), "{}", SourceSection(self))?;
        }

        Ok(())
    }
}

struct SourceSection<'a>(&'a Frame);

impl fmt::Display for SourceSection<'_> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let (lineno, filename) = match (self.0.lineno, self.0.filename.as_ref()) {
            (Some(a), Some(b)) => (a, b),
            // Without a line number and file name, we can't sensibly proceed.
            _ => return Ok(()),
        };

        let file = match std::fs::File::open(filename) {
            Ok(file) => file,
            Err(ref e) if e.kind() == std::io::ErrorKind::NotFound => return Ok(()),
            e @ Err(_) => e.unwrap(),
        };

        use std::fmt::Write;
        use std::io::BufRead;

        // Extract relevant lines.
        let reader = std::io::BufReader::new(file);
        let start_line = lineno - 2.min(lineno - 1);
        let surrounding_src = reader.lines().skip(start_line as usize - 1).take(5);
        let mut separated = f.header("\n");
        let mut f = separated.in_progress();
        for (line, cur_line_no) in surrounding_src.zip(start_line..) {
            let line = line.unwrap();
            if cur_line_no == lineno {
                write!(
                    &mut f,
                    "{:>8} {} {}",
                    cur_line_no.white().bold(),
                    ">".white().bold(),
                    line.white().bold()
                )?;
            } else {
                write!(&mut f, "{:>8} │ {}", cur_line_no, line)?;
            }
            f = separated.ready();
        }

        Ok(())
    }
}

impl Frame {
    fn is_dependency_code(&self) -> bool {
        const SYM_PREFIXES: &[&str] = &[
            "std::",
            "core::",
            "backtrace::backtrace::",
            "_rust_begin_unwind",
            "color_traceback::",
            "__rust_",
            "___rust_",
            "__pthread",
            "_main",
            "main",
            "__scrt_common_main_seh",
            "BaseThreadInitThunk",
            "_start",
            "__libc_start_main",
            "start_thread",
        ];

        // Inspect name.
        if let Some(ref name) = self.name {
            if SYM_PREFIXES.iter().any(|x| name.starts_with(x)) {
                return true;
            }
        }

        const FILE_PREFIXES: &[&str] = &[
            "/rustc/",
            "src/libstd/",
            "src/libpanic_unwind/",
            "src/libtest/",
        ];

        // Inspect filename.
        if let Some(ref filename) = self.filename {
            let filename = filename.to_string_lossy();
            if FILE_PREFIXES.iter().any(|x| filename.starts_with(x))
                || filename.contains("/.cargo/registry/src/")
            {
                return true;
            }
        }

        false
    }

    /// Heuristically determine whether a frame is likely to be a post panic
    /// frame.
    ///
    /// Post panic frames are frames of a functions called after the actual panic
    /// is already in progress and don't contain any useful information for a
    /// reader of the backtrace.
    fn is_post_panic_code(&self) -> bool {
        const SYM_PREFIXES: &[&str] = &[
            "_rust_begin_unwind",
            "rust_begin_unwind",
            "core::result::unwrap_failed",
            "core::option::expect_none_failed",
            "core::panicking::panic_fmt",
            "color_backtrace::create_panic_handler",
            "std::panicking::begin_panic",
            "begin_panic_fmt",
            "failure::backtrace::Backtrace::new",
            "backtrace::capture",
            "failure::error_message::err_msg",
            "<failure::error::Error as core::convert::From<F>>::from",
        ];

        match self.name.as_ref() {
            Some(name) => SYM_PREFIXES.iter().any(|x| name.starts_with(x)),
            None => false,
        }
    }

    /// Heuristically determine whether a frame is likely to be part of language
    /// runtime.
    fn is_runtime_init_code(&self) -> bool {
        const SYM_PREFIXES: &[&str] = &[
            "std::rt::lang_start::",
            "test::run_test::run_test_inner::",
            "std::sys_common::backtrace::__rust_begin_short_backtrace",
        ];

        let (name, file) = match (self.name.as_ref(), self.filename.as_ref()) {
            (Some(name), Some(filename)) => (name, filename.to_string_lossy()),
            _ => return false,
        };

        if SYM_PREFIXES.iter().any(|x| name.starts_with(x)) {
            return true;
        }

        // For Linux, this is the best rule for skipping test init I found.
        if name == "{{closure}}" && file == "src/libtest/lib.rs" {
            return true;
        }

        false
    }
}

/// Builder for customizing the behavior of the global panic and error report hooks
pub struct HookBuilder {
    filters: Vec<Box<FilterCallback>>,
    capture_span_trace_by_default: bool,
    display_env_section: bool,
    panic_section: Option<Box<dyn Display + Send + Sync + 'static>>,
    panic_message: Box<dyn PanicMessage>,
    #[cfg(feature = "issue-url")]
    issue_url: Option<String>,
    #[cfg(feature = "issue-url")]
    issue_metadata: Vec<(String, Box<dyn Display + Send + Sync + 'static>)>,
    #[cfg(feature = "issue-url")]
    issue_filter: Arc<IssueFilterCallback>,
}

impl HookBuilder {
    /// Construct a HookBuilder
    ///
    /// # Details
    ///
    /// By default this function calls `add_default_filters()` and
    /// `capture_span_trace_by_default(true)`. To get a `HookBuilder` with all
    /// features disabled by default call `HookBuilder::blank()`.
    ///
    /// # Example
    ///
    /// ```rust
    /// use color_eyre::config::HookBuilder;
    ///
    /// HookBuilder::new()
    ///     .install()
    ///     .unwrap();
    /// ```
    pub fn new() -> Self {
        Self::blank()
            .add_default_filters()
            .capture_span_trace_by_default(true)
    }

    /// Construct a HookBuilder with minimal features enabled
    pub fn blank() -> Self {
        HookBuilder {
            filters: vec![],
            capture_span_trace_by_default: false,
            display_env_section: true,
            panic_section: None,
            panic_message: Box::new(DefaultPanicMessage),
            #[cfg(feature = "issue-url")]
            issue_url: None,
            #[cfg(feature = "issue-url")]
            issue_metadata: vec![],
            #[cfg(feature = "issue-url")]
            issue_filter: Arc::new(|_| true),
        }
    }

    /// Add a custom section to the panic hook that will be printed
    /// in the panic message.
    ///
    /// # Examples
    ///
    /// ```rust
    /// color_eyre::config::HookBuilder::default()
    ///     .panic_section("consider reporting the bug at https://github.com/yaahc/color-eyre")
    ///     .install()
    ///     .unwrap()
    /// ```
    pub fn panic_section<S: Display + Send + Sync + 'static>(mut self, section: S) -> Self {
        self.panic_section = Some(Box::new(section));
        self
    }

    /// Overrides the main error message printing section at the start of panic
    /// reports
    ///
    /// # Examples
    ///
    /// ```rust
    /// use std::{panic::Location, fmt};
    /// use color_eyre::section::PanicMessage;
    /// use owo_colors::OwoColorize;
    ///
    /// struct MyPanicMessage;
    ///
    /// color_eyre::config::HookBuilder::default()
    ///     .panic_message(MyPanicMessage)
    ///     .install()
    ///     .unwrap();
    ///
    /// impl PanicMessage for MyPanicMessage {
    ///     fn display(&self, pi: &std::panic::PanicInfo<'_>, f: &mut fmt::Formatter<'_>) -> fmt::Result {
    ///         writeln!(f, "{}", "The application panicked (crashed).".red())?;
    ///
    ///         // Print panic message.
    ///         let payload = pi
    ///             .payload()
    ///             .downcast_ref::<String>()
    ///             .map(String::as_str)
    ///             .or_else(|| pi.payload().downcast_ref::<&str>().cloned())
    ///             .unwrap_or("<non string panic payload>");
    ///
    ///         write!(f, "Message:  ")?;
    ///         writeln!(f, "{}", payload.cyan())?;
    ///
    ///         // If known, print panic location.
    ///         write!(f, "Location: ")?;
    ///         if let Some(loc) = pi.location() {
    ///             write!(f, "{}", loc.file().purple())?;
    ///             write!(f, ":")?;
    ///             write!(f, "{}", loc.line().purple())?;
    ///
    ///             write!(f, "\n\nConsider reporting the bug at {}", custom_url(loc, payload))?;
    ///         } else {
    ///             write!(f, "<unknown>")?;
    ///         }
    ///
    ///         Ok(())
    ///     }
    /// }
    ///
    /// fn custom_url(location: &Location<'_>, message: &str) -> impl fmt::Display {
    ///     "todo"
    /// }
    /// ```
    pub fn panic_message<S: PanicMessage>(mut self, section: S) -> Self {
        self.panic_message = Box::new(section);
        self
    }

    /// Set an upstream github repo and enable issue reporting url generation
    ///
    /// # Details
    ///
    /// Once enabled, color-eyre will generate urls that will create customized
    /// issues pre-populated with information about the associated error report.
    ///
    /// Additional information can be added to the metadata table in the
    /// generated urls by calling `add_issue_metadata` when configuring the
    /// HookBuilder.
    ///
    /// # Examples
    ///
    /// ```rust
    /// color_eyre::config::HookBuilder::default()
    ///     .issue_url(concat!(env!("CARGO_PKG_REPOSITORY"), "/issues/new"))
    ///     .install()
    ///     .unwrap();
    /// ```
    #[cfg(feature = "issue-url")]
    #[cfg_attr(docsrs, doc(cfg(feature = "issue-url")))]
    pub fn issue_url<S: ToString>(mut self, url: S) -> Self {
        self.issue_url = Some(url.to_string());
        self
    }

    /// Add a new entry to the metadata table in generated github issue urls
    ///
    /// **Note**: this metadata will be ignored if no `issue_url` is set.
    ///
    /// # Examples
    ///
    /// ```rust
    /// color_eyre::config::HookBuilder::default()
    ///     .issue_url(concat!(env!("CARGO_PKG_REPOSITORY"), "/issues/new"))
    ///     .add_issue_metadata("version", env!("CARGO_PKG_VERSION"))
    ///     .install()
    ///     .unwrap();
    /// ```
    #[cfg(feature = "issue-url")]
    #[cfg_attr(docsrs, doc(cfg(feature = "issue-url")))]
    pub fn add_issue_metadata<K, V>(mut self, key: K, value: V) -> Self
    where
        K: Display,
        V: Display + Send + Sync + 'static,
    {
        let pair = (key.to_string(), Box::new(value) as _);
        self.issue_metadata.push(pair);
        self
    }

    /// Configures a filter for disabling issue url generation for certain kinds of errors
    ///
    /// If the closure returns `true`, then the issue url will be generated.
    ///
    /// # Examples
    ///
    /// ```rust
    /// color_eyre::config::HookBuilder::default()
    ///     .issue_url(concat!(env!("CARGO_PKG_REPOSITORY"), "/issues/new"))
    ///     .issue_filter(|kind| match kind {
    ///         color_eyre::ErrorKind::NonRecoverable(payload) => {
    ///             let payload = payload
    ///                 .downcast_ref::<String>()
    ///                 .map(String::as_str)
    ///                 .or_else(|| payload.downcast_ref::<&str>().cloned())
    ///                 .unwrap_or("<non string panic payload>");
    ///
    ///             !payload.contains("my irrelevant error message")
    ///         },
    ///         color_eyre::ErrorKind::Recoverable(error) => !error.is::<std::fmt::Error>(),
    ///     })
    ///     .install()
    ///     .unwrap();
    ///
    #[cfg(feature = "issue-url")]
    #[cfg_attr(docsrs, doc(cfg(feature = "issue-url")))]
    pub fn issue_filter<F>(mut self, predicate: F) -> Self
    where
        F: Fn(crate::ErrorKind<'_>) -> bool + Send + Sync + 'static,
    {
        self.issue_filter = Arc::new(predicate);
        self
    }

    /// Configures the default capture mode for `SpanTraces` in error reports and panics
    pub fn capture_span_trace_by_default(mut self, cond: bool) -> Self {
        self.capture_span_trace_by_default = cond;
        self
    }

    /// Configures the enviroment varible info section and whether or not it is displayed
    pub fn display_env_section(mut self, cond: bool) -> Self {
        self.display_env_section = cond;
        self
    }

    /// Add a custom filter to the set of frame filters
    ///
    /// # Examples
    ///
    /// ```rust
    /// color_eyre::config::HookBuilder::default()
    ///     .add_frame_filter(Box::new(|frames| {
    ///         let filters = &[
    ///             "uninteresting_function",
    ///         ];
    ///
    ///         frames.retain(|frame| {
    ///             !filters.iter().any(|f| {
    ///                 let name = if let Some(name) = frame.name.as_ref() {
    ///                     name.as_str()
    ///                 } else {
    ///                     return true;
    ///                 };
    ///
    ///                 name.starts_with(f)
    ///             })
    ///         });
    ///     }))
    ///     .install()
    ///     .unwrap();
    /// ```
    pub fn add_frame_filter(mut self, filter: Box<FilterCallback>) -> Self {
        self.filters.push(filter);
        self
    }

    /// Install the given Hook as the global error report hook
    pub fn install(self) -> Result<(), crate::eyre::Report> {
        let (panic_hook, eyre_hook) = self.into_hooks();
        crate::eyre::set_hook(Box::new(move |e| Box::new(eyre_hook.default(e))))?;
        install_panic_hook();

        if crate::CONFIG.set(panic_hook).is_err() {
            Err(InstallError)?
        }

        Ok(())
    }

    /// Add the default set of filters to this `HookBuilder`'s configuration
    pub fn add_default_filters(self) -> Self {
        self.add_frame_filter(Box::new(default_frame_filter))
            .add_frame_filter(Box::new(eyre_frame_filters))
    }

    pub(crate) fn into_hooks(self) -> (PanicHook, EyreHook) {
        #[cfg(feature = "issue-url")]
        let metadata = Arc::new(self.issue_metadata);
        let panic_hook = PanicHook {
            filters: self.filters.into_iter().map(Into::into).collect(),
            section: self.panic_section,
            #[cfg(feature = "capture-spantrace")]
            capture_span_trace_by_default: self.capture_span_trace_by_default,
            display_env_section: self.display_env_section,
            panic_message: self.panic_message,
            #[cfg(feature = "issue-url")]
            issue_url: self.issue_url.clone(),
            #[cfg(feature = "issue-url")]
            issue_metadata: metadata.clone(),
            #[cfg(feature = "issue-url")]
            issue_filter: self.issue_filter.clone(),
        };

        let eyre_hook = EyreHook {
            #[cfg(feature = "capture-spantrace")]
            capture_span_trace_by_default: self.capture_span_trace_by_default,
            display_env_section: self.display_env_section,
            #[cfg(feature = "issue-url")]
            issue_url: self.issue_url,
            #[cfg(feature = "issue-url")]
            issue_metadata: metadata,
            #[cfg(feature = "issue-url")]
            issue_filter: self.issue_filter,
        };

        (panic_hook, eyre_hook)
    }
}

#[allow(missing_docs)]
impl Default for HookBuilder {
    fn default() -> Self {
        Self::new()
    }
}

fn default_frame_filter(frames: &mut Vec<&Frame>) {
    let top_cutoff = frames
        .iter()
        .rposition(|x| x.is_post_panic_code())
        .map(|x| x + 2) // indices are 1 based
        .unwrap_or(0);

    let bottom_cutoff = frames
        .iter()
        .position(|x| x.is_runtime_init_code())
        .unwrap_or_else(|| frames.len());

    let rng = top_cutoff..=bottom_cutoff;
    frames.retain(|x| rng.contains(&x.n))
}

fn eyre_frame_filters(frames: &mut Vec<&Frame>) {
    let filters = &[
        "<color_eyre::Handler as eyre::EyreHandler>::default",
        "eyre::",
        "color_eyre::",
    ];

    frames.retain(|frame| {
        !filters.iter().any(|f| {
            let name = if let Some(name) = frame.name.as_ref() {
                name.as_str()
            } else {
                return true;
            };

            name.starts_with(f)
        })
    });
}

struct PanicPrinter<'a>(&'a std::panic::PanicInfo<'a>);

impl fmt::Display for PanicPrinter<'_> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        print_panic_info(self, f)
    }
}

fn install_panic_hook() {
    std::panic::set_hook(Box::new(|pi| eprintln!("{}", PanicPrinter(pi))))
}

struct DefaultPanicMessage;

impl PanicMessage for DefaultPanicMessage {
    fn display(&self, pi: &std::panic::PanicInfo<'_>, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        writeln!(f, "{}", "The application panicked (crashed).".red())?;

        // Print panic message.
        let payload = pi
            .payload()
            .downcast_ref::<String>()
            .map(String::as_str)
            .or_else(|| pi.payload().downcast_ref::<&str>().cloned())
            .unwrap_or("<non string panic payload>");

        write!(f, "Message:  ")?;
        writeln!(f, "{}", payload.cyan())?;

        // If known, print panic location.
        write!(f, "Location: ")?;
        if let Some(loc) = pi.location() {
            write!(f, "{}", loc.file().purple())?;
            write!(f, ":")?;
            write!(f, "{}", loc.line().purple())?;
        } else {
            write!(f, "<unknown>")?;
        }

        Ok(())
    }
}

fn print_panic_info(printer: &PanicPrinter<'_>, out: &mut fmt::Formatter<'_>) -> fmt::Result {
    let hook = installed_hook();
    hook.panic_message.display(printer.0, out)?;

    let v = panic_verbosity();
    let capture_bt = v != Verbosity::Minimal;

    #[cfg(feature = "capture-spantrace")]
    let span_trace = if hook.spantrace_capture_enabled() {
        Some(tracing_error::SpanTrace::capture())
    } else {
        None
    };

    let bt = if capture_bt {
        Some(backtrace::Backtrace::new())
    } else {
        None
    };

    let mut separated = out.header("\n\n");

    if let Some(ref section) = hook.section {
        write!(&mut separated.ready(), "{}", section)?;
    }

    #[cfg(feature = "capture-spantrace")]
    {
        if let Some(span_trace) = span_trace.as_ref() {
            write!(
                &mut separated.ready(),
                "{}",
                crate::writers::FormattedSpanTrace(span_trace)
            )?;
        }
    }

    if let Some(bt) = bt.as_ref() {
        let fmted_bt = hook.format_backtrace(&bt);
        write!(
            indented(&mut separated.ready()).with_format(Format::Uniform { indentation: "  " }),
            "{}",
            fmted_bt
        )?;
    }

    if hook.display_env_section {
        let env_section = EnvSection {
            bt_captured: &capture_bt,
            #[cfg(feature = "capture-spantrace")]
            span_trace: span_trace.as_ref(),
        };

        write!(&mut separated.ready(), "{}", env_section)?;
    }

    #[cfg(feature = "issue-url")]
    {
        let payload = printer.0.payload();

        if hook.issue_url.is_some()
            && (*hook.issue_filter)(crate::ErrorKind::NonRecoverable(payload))
        {
            let url = hook.issue_url.as_ref().unwrap();
            let payload = payload
                .downcast_ref::<String>()
                .map(String::as_str)
                .or_else(|| payload.downcast_ref::<&str>().cloned())
                .unwrap_or("<non string panic payload>");

            let issue_section = crate::section::github::IssueSection::new(url, payload)
                .with_backtrace(bt.as_ref())
                .with_location(printer.0.location())
                .with_metadata(&**hook.issue_metadata);

            #[cfg(feature = "capture-spantrace")]
            let issue_section = issue_section.with_span_trace(span_trace.as_ref());

            write!(&mut separated.ready(), "{}", issue_section)?;
        }
    }

    Ok(())
}

pub(crate) struct PanicHook {
    filters: Vec<Arc<FilterCallback>>,
    section: Option<Box<dyn Display + Send + Sync + 'static>>,
    panic_message: Box<dyn PanicMessage>,
    #[cfg(feature = "capture-spantrace")]
    capture_span_trace_by_default: bool,
    display_env_section: bool,
    #[cfg(feature = "issue-url")]
    issue_url: Option<String>,
    #[cfg(feature = "issue-url")]
    issue_metadata: Arc<Vec<(String, Box<dyn Display + Send + Sync + 'static>)>>,
    #[cfg(feature = "issue-url")]
    issue_filter: Arc<IssueFilterCallback>,
}

impl PanicHook {
    pub(crate) fn format_backtrace<'a>(
        &'a self,
        trace: &'a backtrace::Backtrace,
    ) -> BacktraceFormatter<'a> {
        BacktraceFormatter {
            printer: self,
            inner: trace,
        }
    }

    #[cfg(feature = "capture-spantrace")]
    fn spantrace_capture_enabled(&self) -> bool {
        std::env::var("RUST_SPANTRACE")
            .map(|val| val != "0")
            .unwrap_or(self.capture_span_trace_by_default)
    }
}

pub(crate) struct EyreHook {
    #[cfg(feature = "capture-spantrace")]
    capture_span_trace_by_default: bool,
    display_env_section: bool,
    #[cfg(feature = "issue-url")]
    issue_url: Option<String>,
    #[cfg(feature = "issue-url")]
    issue_metadata: Arc<Vec<(String, Box<dyn Display + Send + Sync + 'static>)>>,
    #[cfg(feature = "issue-url")]
    issue_filter: Arc<IssueFilterCallback>,
}

impl EyreHook {
    #[allow(unused_variables)]
    pub(crate) fn default(&self, error: &(dyn std::error::Error + 'static)) -> crate::Handler {
        let backtrace = if lib_verbosity() != Verbosity::Minimal {
            Some(backtrace::Backtrace::new())
        } else {
            None
        };

        #[cfg(feature = "capture-spantrace")]
        let span_trace = if self.spantrace_capture_enabled()
            && crate::handler::get_deepest_spantrace(error).is_none()
        {
            Some(tracing_error::SpanTrace::capture())
        } else {
            None
        };

        crate::Handler {
            backtrace,
            #[cfg(feature = "capture-spantrace")]
            span_trace,
            sections: Vec::new(),
            display_env_section: self.display_env_section,
            #[cfg(feature = "issue-url")]
            issue_url: self.issue_url.clone(),
            #[cfg(feature = "issue-url")]
            issue_metadata: self.issue_metadata.clone(),
            #[cfg(feature = "issue-url")]
            issue_filter: self.issue_filter.clone(),
        }
    }

    #[cfg(feature = "capture-spantrace")]
    fn spantrace_capture_enabled(&self) -> bool {
        std::env::var("RUST_SPANTRACE")
            .map(|val| val != "0")
            .unwrap_or(self.capture_span_trace_by_default)
    }
}

pub(crate) struct BacktraceFormatter<'a> {
    printer: &'a PanicHook,
    inner: &'a backtrace::Backtrace,
}

impl fmt::Display for BacktraceFormatter<'_> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{:━^80}", " BACKTRACE ")?;

        // Collect frame info.
        let frames: Vec<_> = self
            .inner
            .frames()
            .iter()
            .flat_map(|frame| frame.symbols())
            .zip(1usize..)
            .map(|(sym, n)| Frame {
                name: sym.name().map(|x| x.to_string()),
                lineno: sym.lineno(),
                filename: sym.filename().map(|x| x.into()),
                n,
            })
            .collect();

        let mut filtered_frames = frames.iter().collect();
        match env::var("COLORBT_SHOW_HIDDEN").ok().as_deref() {
            Some("1") | Some("on") | Some("y") => (),
            _ => {
                for filter in &self.printer.filters {
                    filter(&mut filtered_frames);
                }
            }
        }

        if filtered_frames.is_empty() {
            // TODO: Would probably look better centered.
            return write!(f, "\n<empty backtrace>");
        }

        let mut separated = f.header("\n");

        // Don't let filters mess with the order.
        filtered_frames.sort_by_key(|x| x.n);

        let mut buf = String::new();

        macro_rules! print_hidden {
            ($n:expr) => {
                let n = $n;
                buf.clear();
                write!(
                    &mut buf,
                    "{decorator} {n} frame{plural} hidden {decorator}",
                    n = n,
                    plural = if n == 1 { "" } else { "s" },
                    decorator = "⋮",
                )
                .expect("writing to strings doesn't panic");
                write!(&mut separated.ready(), "{:^80}", buf.bright_cyan())?;
            };
        }

        let mut last_n = 0;
        for frame in &filtered_frames {
            let frame_delta = frame.n - last_n - 1;
            if frame_delta != 0 {
                print_hidden!(frame_delta);
            }
            write!(&mut separated.ready(), "{}", frame)?;
            last_n = frame.n;
        }

        let last_filtered_n = filtered_frames.last().unwrap().n;
        let last_unfiltered_n = frames.last().unwrap().n;
        if last_filtered_n < last_unfiltered_n {
            print_hidden!(last_unfiltered_n - last_filtered_n);
        }

        Ok(())
    }
}

pub(crate) fn installed_hook() -> &'static PanicHook {
    crate::CONFIG.get_or_init(default_printer)
}

fn default_printer() -> PanicHook {
    let (panic_hook, _) = HookBuilder::default().into_hooks();
    panic_hook
}

#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Copy)]
pub(crate) enum Verbosity {
    Minimal,
    Medium,
    Full,
}

pub(crate) fn panic_verbosity() -> Verbosity {
    match env::var("RUST_BACKTRACE") {
        Ok(s) if s == "full" => Verbosity::Full,
        Ok(s) if s != "0" => Verbosity::Medium,
        _ => Verbosity::Minimal,
    }
}

pub(crate) fn lib_verbosity() -> Verbosity {
    match env::var("RUST_LIB_BACKTRACE").or_else(|_| env::var("RUST_BACKTRACE")) {
        Ok(s) if s == "full" => Verbosity::Full,
        Ok(s) if s != "0" => Verbosity::Medium,
        _ => Verbosity::Minimal,
    }
}

/// Callback for filtering a vector of `Frame`s
pub type FilterCallback = dyn Fn(&mut Vec<&Frame>) + Send + Sync + 'static;

/// Callback for filtering issue url generation in error reports
#[cfg(feature = "issue-url")]
#[cfg_attr(docsrs, doc(cfg(feature = "issue-url")))]
pub type IssueFilterCallback = dyn Fn(crate::ErrorKind<'_>) -> bool + Send + Sync + 'static;