use std::collections::VecDeque;
use std::io::{self, BufRead};

use crate::collapse::common::{self, CollapsePrivate, Occurrences};
use crate::collapse::matcher::is_kernel;

const TIDY_GENERIC: bool = true;
const TIDY_JAVA: bool = true;

mod logging {
    use log::{info, warn};

    pub(super) fn filtering_for_events_of_type(ty: &str) {
        info!("Filtering for events of type: {}", ty);
    }

    pub(super) fn weird_event_line(line: &str) {
        warn!("Weird event line: {}", line);
    }

    pub(super) fn weird_stack_line(line: &str) {
        warn!("Weird stack line: {}", line);
    }
}

#[derive(PartialEq)]
enum StackFilter {
    Keep,
    Skip,
    SkipRemaining,
}

/// `perf` folder configuration options.
#[derive(Clone, Debug)]
#[non_exhaustive]
pub struct Options {
    /// Annotate JIT functions with a `_[j]` suffix.
    ///
    /// Default is `false`.
    pub annotate_jit: bool,

    /// Annotate kernel functions with a `_[k]` suffix.
    ///
    /// Default is `false`.
    pub annotate_kernel: bool,

    /// Only consider samples of the given event type (see `perf list`). If this option is
    /// set to `None`, it will be set to the first encountered event type.
    ///
    /// Default is `None`.
    pub event_filter: Option<String>,

    /// Include raw addresses (e.g., `0xbfff0836`) where symbols can't be found.
    ///
    /// Default is `false`.
    pub include_addrs: bool,

    /// Include PID in the root frame. If disabled, the root frame is given the name of the
    /// profiled process.
    ///
    /// Default is `false`.
    pub include_pid: bool,

    /// Include TID and PID in the root frame. Implies `include_pid`.
    ///
    /// Default is `false`.
    pub include_tid: bool,

    /// The number of threads to use.
    ///
    /// Default is the number of logical cores on your machine.
    pub nthreads: usize,

    /// If a stack function name is equal to any of the specified strings it will omit all the
    /// following stackframes for that event.
    /// In case no function is matched the whole stack is returned.
    /// Default is not omitting any.
    pub skip_after: Vec<String>,
}

impl Default for Options {
    fn default() -> Self {
        Self {
            annotate_jit: false,
            annotate_kernel: false,
            event_filter: None,
            include_addrs: false,
            include_pid: false,
            include_tid: false,
            nthreads: *common::DEFAULT_NTHREADS,
            skip_after: Vec::default(),
        }
    }
}

/// A stack collapser for the output of `perf script`.
///
/// To construct one, either use `perf::Folder::default()` or create an [`Options`] and use
/// `perf::Folder::from(options)`.
pub struct Folder {
    // State...
    /// General String cache that can be used while processing lines. Currently only used to keep
    /// track of functions for Java inlining.
    cache_line: Vec<String>,

    /// Similar to, but different from, the `event_filter` field on `Options`
    ///
    /// * Field on `Options` represents user's provided configuration and will never change.
    /// * This field, on the other hand, although initially set to the user's provided
    ///   configuration, represents state that may change as data is processed. In particular, if
    ///   the user provided `None` for their initial configuration, this field **will** change to
    ///   `Some(<event type>)` when we encounter the first event during processing. Merging together
    ///   different event types, such as instructions and cycles, would produce misleading results.
    event_filter: Option<String>,

    /// All lines until the next empty line are stack lines.
    in_event: bool,

    /// The number of stacks per job to send to the threadpool.
    nstacks_per_job: usize,

    /// Current comm name.
    ///
    /// Called pname after original stackcollapse-perf source.
    pname: String,

    /// Whether to skip stack lines in this event.
    stack_filter: StackFilter,

    /// Function entries on the stack in this entry thus far.
    stack: VecDeque<String>,

    // Options...
    opt: Options,
}

impl From<Options> for Folder {
    fn from(mut opt: Options) -> Self {
        if opt.nthreads == 0 {
            opt.nthreads = 1;
        }
        opt.include_pid = opt.include_pid || opt.include_tid;
        Self {
            cache_line: Vec::default(),
            event_filter: opt.event_filter.clone(),
            in_event: false,
            nstacks_per_job: common::DEFAULT_NSTACKS_PER_JOB,
            pname: String::default(),
            stack_filter: StackFilter::Keep,
            stack: VecDeque::default(),
            opt,
        }
    }
}

impl Default for Folder {
    fn default() -> Self {
        Options::default().into()
    }
}

impl CollapsePrivate for Folder {
    fn pre_process<R>(&mut self, reader: &mut R, occurrences: &mut Occurrences) -> io::Result<()>
    where
        R: io::BufRead,
    {
        // If user has provided an event filter, do nothing...
        if self.event_filter.is_some() {
            return Ok(());
        }

        // Otherwise, we don't know what the event filter should be; so process
        // the first stack to figure it out (the worker threads need this
        // information to get started). Only read one stack, however, as we would
        // like the remaining stacks to be processed on the worker threads.
        let mut line_buffer = Vec::new();
        let eof = self.process_single_stack(&mut line_buffer, reader, occurrences)?;

        if eof {
            // If we hit EOF, it may be that the input was completely empty.
            // In that case, we don't do the event_filter assertion below.
            return Ok(());
        }

        // If we didn't find an event filter, there is something wrong with
        // our processing code.
        assert!(self.event_filter.is_some());

        Ok(())
    }

    fn collapse_single_threaded<R>(
        &mut self,
        mut reader: R,
        occurrences: &mut Occurrences,
    ) -> io::Result<()>
    where
        R: io::BufRead,
    {
        // While there are still stacks left to process, process them...
        let mut line_buffer = Vec::new();
        while !self.process_single_stack(&mut line_buffer, &mut reader, occurrences)? {}

        // Reset state...
        self.in_event = false;
        self.stack_filter = StackFilter::Keep;
        self.stack.clear();
        Ok(())
    }

    fn is_applicable(&mut self, input: &str) -> Option<bool> {
        // Check if the input has an event line followed by a stack line.

        let mut last_line_was_event_line = false;
        let mut input = input.as_bytes();
        let mut line = String::new();
        loop {
            line.clear();
            if let Ok(n) = input.read_line(&mut line) {
                if n == 0 {
                    break;
                }
            } else {
                return Some(false);
            }

            let line = line.trim();
            // Skip comments
            if line.starts_with('#') {
                continue;
            }

            if line.is_empty() {
                last_line_was_event_line = false;
                continue;
            }

            if last_line_was_event_line {
                // If this is valid input this line should be a stack line.
                return Some(Self::stack_line_parts(line).is_some());
            } else {
                if Self::event_line_parts(line).is_none() {
                    // The first line that's not empty or a comment should be an event line.
                    return Some(false);
                }
                last_line_was_event_line = true;
            }
        }
        None
    }

    fn would_end_stack(&mut self, line: &[u8]) -> bool {
        line.iter().all(|b| (*b as char).is_whitespace())
    }

    fn clone_and_reset_stack_context(&self) -> Self {
        Self {
            cache_line: self.cache_line.clone(),
            event_filter: self.event_filter.clone(),
            in_event: false,
            nstacks_per_job: self.nstacks_per_job,
            pname: String::new(),
            stack_filter: StackFilter::Keep,
            stack: VecDeque::default(),
            opt: self.opt.clone(),
        }
    }

    fn nstacks_per_job(&self) -> usize {
        self.nstacks_per_job
    }

    fn set_nstacks_per_job(&mut self, n: usize) {
        self.nstacks_per_job = n;
    }

    fn nthreads(&self) -> usize {
        self.opt.nthreads
    }

    fn set_nthreads(&mut self, n: usize) {
        self.opt.nthreads = n;
    }
}

impl Folder {
    /// Processes a stack. On success, returns `true` if at end of data; `false` otherwise.
    fn process_single_stack<R>(
        &mut self,
        line_buffer: &mut Vec<u8>,
        reader: &mut R,
        occurrences: &mut Occurrences,
    ) -> io::Result<bool>
    where
        R: io::BufRead,
    {
        loop {
            line_buffer.clear();
            if reader.read_until(0x0A, line_buffer)? == 0 {
                if !self.stack.is_empty() {
                    self.after_event(occurrences);
                }
                return Ok(true);
            }
            let line = String::from_utf8_lossy(line_buffer);
            if line.starts_with('#') {
                continue;
            }
            let line = line.trim_end();
            if line.is_empty() {
                self.after_event(occurrences);
                return Ok(false);
            } else if self.in_event {
                self.on_stack_line(line);
            } else {
                assert!(self.stack.is_empty());
                self.on_event_line(line);
                if !self.stack.is_empty() {
                    // we must have hit a combined event/stack line
                    self.after_event(occurrences);
                }
            }
        }
    }

    fn event_line_parts(line: &str) -> Option<(&str, &str, &str, usize)> {
        let mut word_start = 0;
        let mut all_digits = false;
        let mut last_was_space = false;
        let mut contains_slash_at = None;
        for (idx, c) in line.char_indices() {
            if c == ' ' {
                if all_digits && !last_was_space {
                    // found an all-digit word
                    let (pid, tid) = if let Some(slash) = contains_slash_at {
                        // found PID + TID
                        (&line[word_start..slash], &line[(slash + 1)..idx])
                    } else {
                        // found TID
                        ("?", &line[word_start..idx])
                    };
                    // also trim comm in case multiple spaces were used to separate
                    let comm = line[..(word_start - 1)].trim();
                    return Some((comm, pid, tid, idx + 1));
                }
                word_start = idx + 1;
                all_digits = true;
            } else if c == '/' {
                if all_digits {
                    contains_slash_at = Some(idx);
                }
            } else if c.is_ascii_digit() {
                // we're still all digits if we were all digits
            } else {
                all_digits = false;
                contains_slash_at = None;
            }
            last_was_space = c == ' ';
        }
        None
    }

    // we have an event line, like:
    //
    //     java 25607 4794564.109216: cycles:
    //     java 12688 [002] 6544038.708352: cpu-clock:
    //     V8 WorkerThread 25607 4794564.109216: cycles:
    //     java 24636/25607 [000] 4794564.109216: cycles:
    //     java 12688/12764 6544038.708352: cpu-clock:
    //     V8 WorkerThread 24636/25607 [000] 94564.109216: cycles:
    //     vote   913    72.176760:     257597 cycles:uppp:
    //     false 64414 20110.539270:      34467 cycles:u:  ffffffff9aa3c8de [unknown] ([unknown])
    fn on_event_line(&mut self, line: &str) {
        self.in_event = true;

        if let Some((comm, pid, tid, end)) = Self::event_line_parts(line) {
            let mut by_colons = line[end..].splitn(3, ':').skip(1);
            let event = by_colons
                .next()
                .and_then(|has_event| has_event.rsplit(' ').next());
            if let Some(event) = event {
                if let Some(ref event_filter) = self.event_filter {
                    if event != event_filter {
                        self.stack_filter = StackFilter::Skip;
                        return;
                    }
                } else {
                    // By default only show events of the first encountered event type.
                    // Merging together different types, such as instructions and cycles,
                    // produces misleading results.
                    logging::filtering_for_events_of_type(event);
                    self.event_filter = Some(event.to_string());
                }
            }

            // some event lines _include_ a stack line if the stack only has one frame.
            // in that case, the event will be followed by the stack.
            let single_stack = if let Some(post_event) = by_colons.next() {
                // we need to deal with a couple of cases here:
                //
                //     vote   913    72.176760:     257597 cycles:uppp:
                //     false 64414 20110.539270:      34467 cycles:u:  ffffffff9aa3c8de [unknown] ([unknown])
                //     false 64414 20110.539270:      34467 cycles:  ffffffff9aa3c8de [unknown] ([unknown])
                //
                // the first should not be handled as a stack, whereas the latter two both should
                // the trick is going to be to trim until we encounter a space or a :, whichever
                // comes first, and then evaluate from there.
                let post_event_start = post_event
                    .find(|c| c == ':' || c == ' ')
                    .map(|i| i + 1)
                    .unwrap_or(0);
                let post_event = post_event[post_event_start..].trim();
                if !post_event.is_empty() {
                    // we have a stack!
                    Some(post_event)
                } else {
                    None
                }
            } else {
                None
            };

            // XXX: re-use existing memory in pname if possible
            self.pname = comm.replace(' ', "_");
            if self.opt.include_tid {
                self.pname.push('-');
                self.pname.push_str(pid);
                self.pname.push('/');
                self.pname.push_str(tid);
            } else if self.opt.include_pid {
                self.pname.push('-');
                self.pname.push_str(pid);
            }

            if let Some(stack_line) = single_stack {
                self.on_stack_line(stack_line);
                self.in_event = false;
            }
        } else {
            logging::weird_event_line(line);
            self.in_event = false;
        }
    }

    fn stack_line_parts(line: &str) -> Option<(&str, &str, &str)> {
        let mut line = line.trim_start().splitn(2, ' ');
        let pc = line.next()?.trim_end();
        let mut line = line.next()?.rsplitn(2, ' ');
        let mut module = line.next()?;

        // Module should always be wrapped in (), so remove those if they exist.
        // We first check for their existence because it's possible this is being
        // called from `is_applicable` on a non-perf profile. This both prevents
        // a panic if `module.len() < 1` and helps detect whether or not we're
        // parsing a `perf` profile and not something else.
        if !module.starts_with('(') || !module.ends_with(')') {
            return None;
        }
        module = &module[1..(module.len() - 1)];

        let rawfunc = match line.next()?.trim() {
            // Sometimes there are two spaces between the pc and the (, like:
            //     7f1e2215d058  (/lib/x86_64-linux-gnu/libc-2.15.so)
            // In order to match the perl version, the rawfunc should be " ", and not "".
            "" => " ",
            s => s,
        };
        Some((pc, rawfunc, module))
    }

    // we have a stack line that shows one stack entry from the preceding event, like:
    //
    //     ffffffff8103ce3b native_safe_halt ([kernel.kallsyms])
    //     ffffffff8101c6a3 default_idle ([kernel.kallsyms])
    //     ffffffff81013236 cpu_idle ([kernel.kallsyms])
    //     ffffffff815bf03e rest_init ([kernel.kallsyms])
    //     ffffffff81aebbfe start_kernel ([kernel.kallsyms].init.text)
    //     7f533952bc77 _dl_check_map_versions+0x597 (/usr/lib/ld-2.28.so)
    //     7f53389994d0 [unknown] ([unknown])
    //                0 [unknown] ([unknown])
    fn on_stack_line(&mut self, line: &str) {
        let should_omit = matches!(
            self.stack_filter,
            StackFilter::Skip | StackFilter::SkipRemaining
        );
        if should_omit {
            return;
        }

        if let Some((pc, mut rawfunc, module)) = Self::stack_line_parts(line) {
            // Strip off symbol offsets
            if let Some(offset) = rawfunc.rfind("+0x") {
                let end = &rawfunc[(offset + 3)..];
                if end.chars().all(|c| char::is_ascii_hexdigit(&c)) {
                    // it's a symbol offset!
                    rawfunc = &rawfunc[..offset];
                }
            }

            // skip process names?
            // see https://github.com/brendangregg/FlameGraph/blob/f857ebc94bfe2a9bfdc4f1536ebacfb7466f69ba/stackcollapse-perf.pl#L269
            if rawfunc.starts_with('(') {
                return;
            }

            // perf mostly demangles Rust symbols,
            // but this will fix the things it gets wrong
            let rawfunc = common::fix_partially_demangled_rust_symbol(rawfunc);

            // Support Java inlining by splitting on "->". After the first func, the
            // rest are annotated with "_[i]" to mark them as inlined.
            // See https://github.com/brendangregg/FlameGraph/pull/89.
            for func in rawfunc.split("->") {
                let mut func = with_module_fallback(module, func, pc, self.opt.include_addrs);
                if TIDY_GENERIC {
                    func = tidy_generic(func);
                }

                if TIDY_JAVA && self.pname == "java" {
                    func = tidy_java(func);
                }

                // Annotations
                //
                // detect inlined when self.cache_line has funcs
                // detect kernel from the module name; eg, frames to parse include:
                //
                //     ffffffff8103ce3b native_safe_halt ([kernel.kallsyms])
                //     8c3453 tcp_sendmsg (/lib/modules/4.3.0-rc1-virtual/build/vmlinux)
                //     7d8 ipv4_conntrack_local+0x7f8f80b8 ([nf_conntrack_ipv4])
                //
                // detect jit from the module name; eg:
                //
                //     7f722d142778 Ljava/io/PrintStream;::print (/tmp/perf-19982.map)
                if !self.cache_line.is_empty() {
                    func.push_str("_[i]"); // inlined
                } else if self.opt.annotate_kernel && is_kernel(module) {
                    func.push_str("_[k]"); // kernel
                } else if self.opt.annotate_jit
                    && ((module.starts_with("/tmp/perf-") && module.ends_with(".map"))
                        || (module.contains("/jitted-") && module.ends_with(".so")))
                {
                    func.push_str("_[j]"); // jitted
                }

                self.cache_line.push(func);
            }

            while let Some(func) = self.cache_line.pop() {
                self.stack.push_front(func);
            }

            if self
                .opt
                .skip_after
                .iter()
                .any(|skip_after| rawfunc == *skip_after)
            {
                self.stack_filter = StackFilter::SkipRemaining;
            }
        } else {
            logging::weird_stack_line(line);
        }
    }

    fn after_event(&mut self, occurrences: &mut Occurrences) {
        // end of stack, so emit stack entry
        if !self.stack.is_empty() {
            // allocate a string that is long enough to hold the entire stack string
            let mut stack_str = String::with_capacity(
                self.pname.len() + self.stack.iter().fold(0, |a, s| a + s.len() + 1),
            );

            // If we skip remaining frames we want to skip pname as well.
            if self.stack_filter != StackFilter::SkipRemaining {
                // add the comm name
                stack_str.push_str(&self.pname);
                stack_str.push(';');
            }
            for e in self.stack.drain(..) {
                stack_str.push_str(&e);
                stack_str.push(';');
            }

            // self.stack is not empty, therefore stack_str has at least one frame followed by ';'
            stack_str.pop();

            // count it!
            occurrences.insert_or_add(stack_str, 1);
        }

        // reset for the next event
        self.in_event = false;
        self.stack_filter = StackFilter::Keep;
        self.stack.clear();
    }
}

// massage function name to be nicer
// NOTE: ignoring https://github.com/jvm-profiling-tools/perf-map-agent/pull/35
fn with_module_fallback(module: &str, func: &str, pc: &str, include_addrs: bool) -> String {
    if func != "[unknown]" {
        return func.to_string();
    }

    // try to use part of module name as function if unknown
    let func = match (module, include_addrs) {
        ("[unknown]", true) => "unknown",
        ("[unknown]", false) => {
            // no need to process this further
            return func.to_string();
        }
        (module, _) => {
            // use everything following last / of module as function name
            &module[module.rfind('/').map(|i| i + 1).unwrap_or(0)..]
        }
    };

    // output string is a bit longer than rawfunc but not much
    let mut res = String::with_capacity(func.len() + 12);

    res.push('[');
    res.push_str(func);
    if include_addrs {
        res.push_str(" <");
        res.push_str(pc);
        res.push_str(">]");
    } else {
        res.push(']');
    }

    res
}

fn tidy_generic(mut func: String) -> String {
    func = func.replace(';', ":");
    // remove argument list from function name, but _don't_ remove:
    //
    //  - Go method names like "net/http.(*Client).Do".
    //    see https://github.com/brendangregg/FlameGraph/pull/72
    //  - C++ anonymous namespace annotations.
    //    see https://github.com/brendangregg/FlameGraph/pull/93
    let mut bracket_depth = 0;
    let mut last_dot_index = Option::<usize>::None;
    let mut length_without_parameters = func.len();
    for (idx, c) in func.char_indices() {
        match c {
            '<' | '{' | '[' => {
                bracket_depth += 1;
            }
            '>' | '}' | ']' | ')' => {
                bracket_depth -= 1;
            }
            '(' => {
                // ignore parentheses inside Rust/C++ templates, or C++ lambda stacks {lambda(...)#1}
                // by only considering top-level parentheses
                if bracket_depth == 0 {
                    // Don't remove go functions starting with .(
                    let is_go_function = last_dot_index == Some(idx);
                    // Don't remove C++ anonymous namespaces
                    let is_anonymous_namespace = func[idx..].starts_with("(anonymous namespace)");
                    if !is_go_function && !is_anonymous_namespace {
                        // found start of parameter list
                        length_without_parameters = idx;
                        break;
                    }
                }
                bracket_depth += 1;
            }
            '.' => {
                // insert index + 1 so we can associate it with the opening parentheses for Golang
                last_dot_index = Some(idx + 1);
            }
            _ => (),
        };
    }
    func.truncate(length_without_parameters);

    // The perl version here strips ' and "; we don't do that.
    // see https://github.com/brendangregg/FlameGraph/commit/817c6ea3b92417349605e5715fe6a7cb8cbc9776
    func
}

fn tidy_java(mut func: String) -> String {
    // along with tidy_generic converts the following:
    //     Lorg/mozilla/javascript/ContextFactory;.call(Lorg/mozilla/javascript/ContextAction;)Ljava/lang/Object;
    //     Lorg/mozilla/javascript/ContextFactory;.call(Lorg/mozilla/javascript/C
    //     Lorg/mozilla/javascript/MemberBox;.<init>(Ljava/lang/reflect/Method;)V
    // into:
    //     org/mozilla/javascript/ContextFactory:.call
    //     org/mozilla/javascript/ContextFactory:.call
    //     org/mozilla/javascript/MemberBox:.init
    if func.starts_with('L') && func.contains('/') {
        func.remove(0);
    }

    func
}

#[cfg(test)]
mod tests {
    use std::fs;
    use std::io::Read;
    use std::path::PathBuf;

    use once_cell::sync::Lazy;
    use pretty_assertions::assert_eq;
    use rand::prelude::*;

    use super::*;
    use crate::collapse::common;
    use crate::collapse::Collapse;

    // Test some interesting edge cased for tidy_generic
    #[test]
    fn test_tidy_generic() {
        let test_expectations = [
            (
                "go/build.(*importReader).readByte",
                "go/build.(*importReader).readByte",
            ),
            ("foo<Vec::<usize>>(Vec<usize>)", "foo<Vec::<usize>>"),
            (".run()V", ".run"),
            ("base(BasicType) const", "base"),
            (
                "std::function<void (int, int)>::operator(int, int)",
                "std::function<void (int, int)>::operator",
            ),
            (
                "{lambda(int, int)#2}::operator()",
                "{lambda(int, int)#2}::operator",
            ),
            (
                "(anonymous namespace)::myBar()",
                "(anonymous namespace)::myBar",
            ),
            // Didn't see this anywhere, but it seems like some language may have [] brackets containing parentheses
            ("[(foo)]::bar()", "[(foo)]::bar"),
        ];

        for (input, expected) in test_expectations.iter() {
            assert_eq!(&tidy_generic(input.to_string()), expected);
        }
    }

    static INPUT: Lazy<Vec<PathBuf>> = Lazy::new(|| {
        common::testing::check_flamegraph_git_submodule_initialised();
        [
            "./flamegraph/example-perf-stacks.txt.gz",
            "./flamegraph/test/perf-cycles-instructions-01.txt",
            "./flamegraph/test/perf-dd-stacks-01.txt",
            "./flamegraph/test/perf-funcab-cmd-01.txt",
            "./flamegraph/test/perf-funcab-pid-01.txt",
            "./flamegraph/test/perf-iperf-stacks-pidtid-01.txt",
            "./flamegraph/test/perf-java-faults-01.txt",
            "./flamegraph/test/perf-java-stacks-01.txt",
            "./flamegraph/test/perf-java-stacks-02.txt",
            "./flamegraph/test/perf-js-stacks-01.txt",
            "./flamegraph/test/perf-mirageos-stacks-01.txt",
            "./flamegraph/test/perf-numa-stacks-01.txt",
            "./flamegraph/test/perf-rust-Yamakaky-dcpu.txt",
            "./flamegraph/test/perf-vertx-stacks-01.txt",
            "./tests/data/collapse-perf/empty-line.txt",
            "./tests/data/collapse-perf/go-stacks.txt",
            "./tests/data/collapse-perf/java-inline.txt",
            "./tests/data/collapse-perf/weird-stack-line.txt",
            "./tests/data/collapse-perf/cpp-stacks-std-function.txt",
        ]
        .iter()
        .map(PathBuf::from)
        .collect::<Vec<_>>()
    });

    #[test]
    fn test_collapse_multi_perf() -> io::Result<()> {
        let mut folder = Folder::default();
        common::testing::test_collapse_multi(&mut folder, &INPUT)
    }

    #[test]
    fn test_collapse_multi_perf_simple() -> io::Result<()> {
        common::testing::check_flamegraph_git_submodule_initialised();
        let path = "./flamegraph/test/perf-cycles-instructions-01.txt";
        let mut file = fs::File::open(path)?;
        let mut bytes = Vec::new();
        file.read_to_end(&mut bytes)?;
        let mut folder = Folder::default();
        <Folder as Collapse>::collapse(&mut folder, &bytes[..], io::sink())
    }

    #[test]
    fn test_one_skip_after() -> io::Result<()> {
        let path = "./tests/data/collapse-perf/go-stacks.txt";
        let mut file = fs::File::open(path)?;
        let mut bytes = Vec::new();
        file.read_to_end(&mut bytes)?;
        let mut folder = {
            let options = Options {
                skip_after: vec!["main.init".to_string()],
                ..Default::default()
            };
            Folder::from(options)
        };
        let mut buf_actual = Vec::new();
        <Folder as Collapse>::collapse(&mut folder, &bytes[..], &mut buf_actual)?;
        let lines = std::str::from_utf8(&buf_actual[..]).unwrap().lines();

        // without `skip_after` some collapsed lines would look like:
        // go;[unknown];x_cgo_notify_runtime_init_done;runtime.main;main.init;...
        for line in lines {
            if line.contains("main.init") {
                assert!(line.starts_with("main.init;")); // we removed the frames above "main.init"
            }
        }
        Ok(())
    }

    #[test]
    fn test_multiple_skip_after() -> io::Result<()> {
        let path = "./tests/data/collapse-perf/go-stacks.txt";
        let mut file = fs::File::open(path)?;
        let mut bytes = Vec::new();
        file.read_to_end(&mut bytes)?;
        let mut folder = {
            let options = Options {
                skip_after: vec!["main.init".to_string(), "regexp.compile".to_string()],
                ..Default::default()
            };
            Folder::from(options)
        };
        let mut buf_actual = Vec::new();
        <Folder as Collapse>::collapse(&mut folder, &bytes[..], &mut buf_actual)?;
        let lines = std::str::from_utf8(&buf_actual[..]).unwrap().lines();

        for line in lines {
            if line.contains("regexp.compile") {
                // Collapse some other lines too, just to make sure it works.
                assert!(line.starts_with("regexp.compile;")); // we removed the frames above "regexp.compile"
            } else if line.contains("main.init") {
                // without `skip_after` some collapsed lines would look like:
                // go;[unknown];x_cgo_notify_runtime_init_done;runtime.main;main.init;...
                assert!(line.starts_with("main.init;")); // we removed the frames above "main.init"
            }
        }
        Ok(())
    }

    /// Varies the nstacks_per_job parameter and outputs the 10 fastests configurations by file.
    ///
    /// Command: `cargo test bench_nstacks_perf --release -- --ignored --nocapture`
    #[test]
    #[ignore]
    fn bench_nstacks_perf() -> io::Result<()> {
        let mut folder = Folder::default();
        common::testing::bench_nstacks(&mut folder, &INPUT)
    }

    #[test]
    #[ignore]
    /// Fuzz test the multithreaded collapser.
    ///
    /// Command: `cargo test fuzz_collapse_perf --release -- --ignored --nocapture`
    fn fuzz_collapse_perf() -> io::Result<()> {
        let seed = thread_rng().gen::<u64>();
        println!("Random seed: {}", seed);
        let mut rng = SmallRng::seed_from_u64(seed);

        let mut buf_actual = Vec::new();
        let mut buf_expected = Vec::new();
        let mut count = 0;

        let inputs = common::testing::read_inputs(&INPUT)?;

        loop {
            let nstacks_per_job = rng.gen_range(1..=500);
            let options = Options {
                annotate_jit: rng.gen(),
                annotate_kernel: rng.gen(),
                event_filter: None,
                include_addrs: rng.gen(),
                include_pid: rng.gen(),
                include_tid: rng.gen(),
                nthreads: rng.gen_range(2..=32),
                skip_after: Vec::default(),
            };

            for (path, input) in inputs.iter() {
                buf_actual.clear();
                buf_expected.clear();

                let mut folder = {
                    let mut options = options.clone();
                    options.nthreads = 1;
                    Folder::from(options)
                };
                folder.nstacks_per_job = nstacks_per_job;
                <Folder as Collapse>::collapse(&mut folder, &input[..], &mut buf_expected)?;
                let expected = std::str::from_utf8(&buf_expected[..]).unwrap();

                let mut folder = Folder::from(options.clone());
                folder.nstacks_per_job = nstacks_per_job;
                <Folder as Collapse>::collapse(&mut folder, &input[..], &mut buf_actual)?;
                let actual = std::str::from_utf8(&buf_actual[..]).unwrap();

                if actual != expected {
                    eprintln!(
                        "Failed on file: {}\noptions: {:#?}\n",
                        path.display(),
                        options
                    );
                    assert_eq!(actual, expected);
                }
            }

            count += 1;
            if count % 10 == 0 {
                println!("Successfully ran {} fuzz tests.", count);
            }
        }
    }
}