hegel/

pretty.rs

//! Pretty-printing of generated values.
//!
//! [`Document`] owns one pretty-printed document: its builder methods
//! choose the layout options, [`Document::printer`] exposes the surface to
//! write through, and [`Document::finish`] consumes it to render exactly
//! once at the end.
//!
//! [`PrettyPrinter`] is that write surface, wrapping libhegel's layout
//! engine (an Oppen-style pretty-printer ported from Hypothesis's
//! `hypothesis.vendor.pretty`). Output is built from three primitives:
//! [`PrettyPrinter::text`] emits literal text, [`PrettyPrinter::breakable`]
//! marks a point that renders as a separator when the enclosing group fits
//! on one line and as a newline plus indentation when it does not, and
//! [`PrettyPrinter::begin_group`] / [`PrettyPrinter::end_group`] delimit
//! the groups those decisions are made over. A group either fits — every
//! breakable renders as its separator — or breaks as a whole, outermost
//! groups first.
//!
//! [`PrettyPrintable`] is the protocol a value uses to describe its own
//! representation, in Rust-expression syntax wherever possible. It is
//! implemented for the standard types the generator library produces,
//! derivable for user types with `#[derive(PrettyPrintable)]`, and
//! available for any `Debug` type — without writing an implementation —
//! through [`pretty_print_as_debug!`](crate::pretty_print_as_debug).

use crate::ffi::{PrinterCallError, PrinterHandle};
use std::cell::Cell;
use std::marker::PhantomData;

/// Accept a printer operation's outcome: misuse panics with libhegel's
/// diagnostic, while writing to a dead region — a straggling thread printing
/// after the document was read, or into a region whose anchor was retracted
/// — is a silent no-op, so a writer that outlives its document never brings
/// the process down.
fn tolerate(result: Result<(), PrinterCallError>) {
    match result {
        Ok(()) | Err(PrinterCallError::DeadRegion) => {}
        Err(PrinterCallError::Other(message)) => panic!("{message}"),
    }
}
use crate::test_case::invalid_argument;

/// The line width documents are laid out to when none is configured.
pub(crate) const DEFAULT_MAX_WIDTH: u64 = 79;

/// One pretty-printed document: the owner of its layout options, its
/// content, and its rendering.
///
/// Configure the layout with the builder methods (before anything is
/// printed), write content through [`printer`](Document::printer), and
/// render by consuming the document with [`finish`](Document::finish) —
/// rendering happens exactly once, at the end. The [`PrettyPrinter`] this
/// hands out is write-only, so code that is *given* a printer (a
/// [`PrettyPrintable`] implementation, a
/// [`PrintableGenerator`](crate::PrintableGenerator)) can never render or
/// otherwise observe the document it is contributing to.
///
/// # Example
///
/// ```
/// use hegel::Document;
///
/// let mut doc = Document::new().max_width(10);
/// let p = doc.printer();
/// p.begin_group(1, "[");
/// p.text("first");
/// p.text(",");
/// p.breakable(" ");
/// p.text("second");
/// p.end_group("]");
/// assert_eq!(doc.finish(), "[first,\n second]");
/// ```
#[derive(Debug)]
pub struct Document {
    max_width: u64,
    printer: Option<PrettyPrinter>,
}

impl Document {
    /// Create an empty document with the default layout options (a maximum
    /// line width of 79 characters).
    pub fn new() -> Self {
        Document {
            max_width: DEFAULT_MAX_WIDTH,
            printer: None,
        }
    }

    /// Keep lines within `max_width` characters where the group structure
    /// allows it. Defaults to 79.
    ///
    /// Layout options describe the whole document, so they must be chosen
    /// up front: calling this after [`printer`](Document::printer) has been
    /// used is an error, as is a `max_width` of 0.
    pub fn max_width(mut self, max_width: usize) -> Self {
        if self.printer.is_some() {
            invalid_argument!("max_width must be set before the document is printed to");
        }
        if max_width == 0 {
            invalid_argument!("max_width must be positive");
        }
        self.max_width = max_width as u64;
        self
    }

    /// The printer to write this document's content through.
    pub fn printer(&mut self) -> &mut PrettyPrinter {
        self.printer
            .get_or_insert_with(|| PrettyPrinter::from_handle(PrinterHandle::new(self.max_width)))
    }

    /// Splice any outstanding deferred content into place, lay the document
    /// out, and return it.
    ///
    /// Consuming the document is what makes rendering a once-at-the-end
    /// operation; there is no way to observe a partially built document.
    pub fn finish(mut self) -> String {
        match &mut self.printer {
            Some(printer) => printer.value(),
            None => String::new(),
        }
    }
}

impl Default for Document {
    fn default() -> Self {
        Document::new()
    }
}

/// The write surface of a pretty-printed document.
///
/// See the [module docs](self) for the printing model. Obtained from
/// [`Document::printer`] — or received, already positioned, by printing
/// code such as a [`PrettyPrintable`] implementation. Rejections of the
/// layout protocol (an [`end_group`](PrettyPrinter::end_group) with no open
/// group) panic, since they indicate a bug in the calling printing code.
pub struct PrettyPrinter {
    /// `None` is the no-op printer: every emitting method returns without
    /// doing anything, so one drawing body can serve both the silent and the
    /// printing draw paths.
    handle: Option<PrinterHandle>,
    /// A printer belongs to one thread at a time (it may move — the type is
    /// `Send` — but never be shared), exactly like [`TestCase`]: the region
    /// model makes cross-thread output deterministic only because each
    /// region has a single writer.
    ///
    /// [`TestCase`]: crate::TestCase
    _single_owner: PhantomData<Cell<()>>,
}

impl std::fmt::Debug for PrettyPrinter {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("PrettyPrinter")
            .field("handle", &self.handle)
            .finish()
    }
}

impl PrettyPrinter {
    /// Create a printer that discards everything printed to it.
    ///
    /// This is how a [`PrintableGenerator`](crate::PrintableGenerator) with
    /// one shared drawing body implements its silent path:
    /// [`Generator::do_draw`](crate::Generator::do_draw) simply calls
    /// `self.do_draw_and_print(tc, &mut PrettyPrinter::noop())`. The
    /// contract that both paths consume identical choices then holds by
    /// construction. Guard any expensive formatting with
    /// [`should_print`](PrettyPrinter::should_print) so the silent path
    /// stays cheap.
    pub fn noop() -> Self {
        PrettyPrinter {
            handle: None,
            _single_owner: PhantomData,
        }
    }

    /// Whether printing to this printer produces output: `false` for the
    /// discarding printer returned by [`noop`](PrettyPrinter::noop). Use it
    /// to skip work — formatting a value, say — whose only purpose is to be
    /// printed.
    pub fn should_print(&self) -> bool {
        self.handle.is_some()
    }

    /// Wrap an existing engine printer handle (e.g. a test case's shared
    /// document).
    pub(crate) fn from_handle(handle: PrinterHandle) -> Self {
        PrettyPrinter {
            handle: Some(handle),
            _single_owner: PhantomData,
        }
    }

    /// Emit literal, unbreakable text.
    ///
    /// Newlines in `s` are honored as unconditional line breaks (equivalent
    /// to [`hard_break`](PrettyPrinter::hard_break), so the new line starts
    /// at the current indentation).
    pub fn text(&mut self, s: &str) {
        let Some(handle) = &self.handle else { return };
        let mut first = true;
        for segment in s.split('\n') {
            if !first {
                tolerate(handle.hard_break());
            }
            first = false;
            if !segment.is_empty() {
                tolerate(handle.text(segment));
            }
        }
    }

    /// Emit a potential break point: renders as `sep` if the enclosing group
    /// fits on the current line, and as a newline plus the current
    /// indentation if the group breaks.
    pub fn breakable(&mut self, sep: &str) {
        let Some(handle) = &self.handle else { return };
        tolerate(handle.breakable(sep));
    }

    /// Emit an unconditional newline followed by the current indentation.
    pub fn hard_break(&mut self) {
        let Some(handle) = &self.handle else { return };
        tolerate(handle.hard_break());
    }

    /// Open a group: emit `open`, then increase the indentation applied by
    /// subsequent break points by `indent` (conventionally the width of
    /// `open`, so continuation lines align just inside the delimiter).
    pub fn begin_group(&mut self, indent: usize, open: &str) {
        let Some(handle) = &self.handle else { return };
        tolerate(handle.begin_group(indent as u64, open));
    }

    /// Close the innermost group: undo the indentation its
    /// [`begin_group`](PrettyPrinter::begin_group) added, then emit `close`.
    /// Panics if no group is open.
    pub fn end_group(&mut self, close: &str) {
        let Some(handle) = &self.handle else { return };
        tolerate(handle.end_group(close));
    }

    /// Adjust the indentation applied by subsequent break points by `delta`.
    pub fn shift_indent(&mut self, delta: isize) {
        let Some(handle) = &self.handle else { return };
        tolerate(handle.shift_indent(delta as i64));
    }

    /// Attach a comment to the line currently being written: `text` is
    /// rendered as `  // text` at the end of that line, every group open at
    /// this position is forced to break — nothing else may share a line with
    /// a comment — and the comment is excluded from line-width accounting. A
    /// group forced to break by a comment also breaks before its closing
    /// delimiter, so the delimiter is not caught up in a comment on the
    /// group's last element.
    ///
    /// `text` must not contain newlines; a comment is a single-line
    /// construct.
    pub fn comment(&mut self, text: &str) {
        let Some(handle) = &self.handle else { return };
        tolerate(handle.comment(&format!("  // {text}")));
    }

    /// Splice in any outstanding deferred content, flush pending break
    /// points, and return everything printed so far. Only ever called by an
    /// owner of the document — [`Document::finish`], or the run lifecycle
    /// reading a test case's document — never by printing code, which only
    /// sees the write surface. Panics on a layout error in the printed
    /// content (an unbalanced `end_group` that could only be detected once
    /// the whole document was assembled).
    pub(crate) fn value(&mut self) -> String {
        self.try_value()
            .unwrap_or_else(|message| panic!("{message}"))
    }

    /// [`value`](PrettyPrinter::value), reporting a layout error in the
    /// printed content as an `Err` instead of panicking — for the run
    /// lifecycle, which renders the output of user printing code after the
    /// test body's panic handling has finished and must not let a printing
    /// bug take down the whole run.
    pub(crate) fn try_value(&mut self) -> Result<String, String> {
        let Some(handle) = &self.handle else {
            unreachable!("only rendering printers have their value read");
        };
        let _ = handle.resolve();
        match handle.value() {
            Ok(rendered) => Ok(rendered),
            Err(PrinterCallError::Other(message)) => Err(message),
            Err(PrinterCallError::DeadRegion) => {
                unreachable!("a document's own region never dies before it renders")
            }
        }
    }

    /// Open a speculative region: output printed through the returned
    /// [`Speculation`] is held back until [`Speculation::commit`] emits it or
    /// [`Speculation::abort`] discards it. Dropping the `Speculation` without
    /// committing (e.g. on unwind) aborts it.
    ///
    /// This is how draw-time printing survives rejection: a combinator that
    /// may retract a draw — a filter retry, a rejected collection element —
    /// prints each attempt inside a speculative region and only commits the
    /// accepted one.
    pub fn speculate(&mut self) -> Speculation<'_> {
        if let Some(handle) = &self.handle {
            tolerate(handle.begin_speculative());
        }
        Speculation {
            printer: self,
            resolved: false,
        }
    }
}

/// Cloning a printer opens a *child region*: a hole in the document,
/// anchored at the printer's current position, that the clone writes into.
///
/// Whatever the clone prints — at any later point, from any thread that owns
/// it — appears at the anchor when the document renders, with line-breaking
/// behaving as if it had been printed inline. This is how output crosses
/// threads deterministically (each clone's output lands where the clone was
/// made, however the threads were scheduled), and how a generator whose
/// value's representation is only known during test execution (a
/// Hegel-controlled random number generator, say) prints: it clones the
/// printer at draw time and records into the clone as the value is used.
///
/// A child region dies when the document renders, or when a speculative
/// region its anchor sat inside is aborted; a dead region's writes are
/// silent no-ops, so a clone that outlives its document can keep trying to
/// record without consequence. Cloning a no-op printer yields a no-op
/// printer, and cloning into a dead region yields a printer whose writes
/// discard.
impl Clone for PrettyPrinter {
    fn clone(&self) -> Self {
        let handle = match &self.handle {
            None => None,
            Some(handle) => match handle.deferred() {
                Ok(child) => Some(child),
                Err(PrinterCallError::DeadRegion) => None,
                Err(PrinterCallError::Other(message)) => unreachable!("{message}"),
            },
        };
        PrettyPrinter {
            handle,
            _single_owner: PhantomData,
        }
    }
}

/// An open speculative region on a [`PrettyPrinter`]; see
/// [`PrettyPrinter::speculate`].
#[derive(Debug)]
pub struct Speculation<'a> {
    printer: &'a mut PrettyPrinter,
    resolved: bool,
}

impl Speculation<'_> {
    /// The printer to print the speculative output through.
    pub fn printer(&mut self) -> &mut PrettyPrinter {
        self.printer
    }

    /// Close the region, keeping its output.
    pub fn commit(mut self) {
        self.resolved = true;
        if let Some(handle) = &self.printer.handle {
            tolerate(handle.commit_speculative());
        }
    }

    /// Close the region, discarding its output.
    pub fn abort(mut self) {
        self.resolved = true;
        if let Some(handle) = &self.printer.handle {
            tolerate(handle.abort_speculative());
        }
    }
}

/// Dropping an uncommitted speculation — most importantly during an unwind
/// out of a speculative draw, such as a budget-exhausted `StopTest` or a
/// failed assumption mid-attempt — discards its output, so a partial attempt
/// never corrupts the document. The result is deliberately ignored: this can
/// run during a panic, where a second panic would abort the process.
impl Drop for Speculation<'_> {
    fn drop(&mut self) {
        if !self.resolved {
            if let Some(handle) = &self.printer.handle {
                let _ = handle.abort_speculative();
            }
        }
    }
}

/// Print a `{:?}` representation through the layout machinery.
///
/// The output of a derived `Debug` implementation follows a small grammar —
/// `Name { field: value, … }`, `Name(…)`, `(…)`, `[…]`, `{key: value, …}`,
/// string and character literals, atoms — and this function re-emits it
/// through the printer's group and breakable primitives, so a large value
/// wraps exactly like one printed by `#[derive(PrettyPrintable)]`. Anything
/// that doesn't parse as that grammar (a hand-written `Debug` can produce
/// arbitrary text) is emitted verbatim, with embedded newlines honored as
/// hard breaks.
///
/// This is the engine behind [`pretty_print_as_debug!`](crate::pretty_print_as_debug)
/// and [`print_as_debug`](crate::Generator::print_as_debug); it is exposed
/// for hand-written [`PrettyPrintable`] implementations that want to embed a
/// `Debug` representation in a larger layout.
pub fn print_debug_repr(repr: &str, printer: &mut PrettyPrinter) {
    match DebugRepr::parse(repr) {
        Some(nodes) => emit_debug_nodes(&nodes, printer),
        None => printer.text(repr),
    }
}

/// One parsed piece of a `Debug` representation: literal text, or a
/// delimited group laid out with a breakable point after each comma.
enum DebugNode {
    Leaf(String),
    Group {
        /// The atom glued to the open delimiter (`Some` in `Some(5)`, `Name`
        /// in `Name { … }`); empty for bare tuples, lists, and map braces.
        prefix: String,
        delimiter: char,
        /// Brace group in derived struct style (`Name { … }`, spaces inside
        /// the braces) as opposed to map style (`{… }`).
        named: bool,
        items: Vec<Vec<DebugNode>>,
    },
}

/// Recursive-descent parser over the derived-`Debug` grammar. Any input
/// outside the grammar makes a parsing method return `None`, and the whole
/// representation falls back to verbatim text.
struct DebugRepr {
    chars: Vec<char>,
    pos: usize,
    depth: usize,
}

/// How deeply groups may nest before [`DebugRepr::parse`] gives up. The
/// parser, the emitter, and the parsed tree's destructor all recurse
/// per nesting level, so an unbounded representation would overflow the
/// stack during failure reporting; past this depth the representation is
/// emitted verbatim instead.
const MAX_DEBUG_DEPTH: usize = 64;

impl DebugRepr {
    fn parse(repr: &str) -> Option<Vec<DebugNode>> {
        if repr.contains('\n') {
            return None;
        }
        let mut parser = DebugRepr {
            chars: repr.chars().collect(),
            pos: 0,
            depth: 0,
        };
        let nodes = parser.parse_item()?;
        if parser.pos != parser.chars.len() {
            return None;
        }
        Some(nodes)
    }

    fn peek(&self) -> Option<char> {
        self.chars.get(self.pos).copied()
    }

    fn peek_next(&self) -> Option<char> {
        self.chars.get(self.pos + 1).copied()
    }

    fn bump(&mut self) -> Option<char> {
        let c = self.peek()?;
        self.pos += 1;
        Some(c)
    }

    /// Parse one comma-separated item — literal runs and nested groups —
    /// stopping (without consuming) at a `", "`, a close delimiter, or the
    /// end of the input.
    fn parse_item(&mut self) -> Option<Vec<DebugNode>> {
        let mut nodes = Vec::new();
        let mut text = String::new();
        loop {
            match self.peek() {
                None | Some(']' | ')' | '}') => break,
                Some(',') if self.peek_next() == Some(' ') => break,
                Some(' ') if self.peek_next() == Some('}') => break,
                Some('"' | '\'') => {
                    flush_text(&mut text, &mut nodes);
                    nodes.push(DebugNode::Leaf(self.lex_quoted()?));
                }
                Some(delimiter @ ('[' | '(' | '{')) => {
                    let prefix = take_group_prefix(&mut text, delimiter);
                    flush_text(&mut text, &mut nodes);
                    nodes.push(self.parse_group(prefix)?);
                }
                Some(c) => {
                    text.push(c);
                    self.bump();
                }
            }
        }
        flush_text(&mut text, &mut nodes);
        Some(nodes)
    }

    /// Parse a delimited group whose open delimiter is the current char.
    fn parse_group(&mut self, prefix: String) -> Option<DebugNode> {
        if self.depth == MAX_DEBUG_DEPTH {
            return None;
        }
        self.depth += 1;
        let delimiter = self.bump()?;
        let close = match delimiter {
            '[' => ']',
            '(' => ')',
            _ => '}',
        };
        let named = delimiter == '{' && !prefix.is_empty() && self.peek() == Some(' ');
        if named {
            self.bump();
        }
        let mut items = Vec::new();
        if !named && self.peek() == Some(close) {
            self.bump();
        } else {
            loop {
                items.push(self.parse_item()?);
                match self.peek() {
                    Some(',') if self.peek_next() == Some(' ') => {
                        self.bump();
                        self.bump();
                    }
                    Some(' ') if named && self.peek_next() == Some(close) => {
                        self.bump();
                        self.bump();
                        break;
                    }
                    Some(c) if !named && c == close => {
                        self.bump();
                        break;
                    }
                    _ => return None,
                }
            }
        }
        self.depth -= 1;
        Some(DebugNode::Group {
            prefix,
            delimiter,
            named,
            items,
        })
    }

    /// Lex a string or character literal, including its quotes. A backslash
    /// escapes the following character, which is all the lexer needs: no
    /// escape sequence contains an unescaped closing quote.
    fn lex_quoted(&mut self) -> Option<String> {
        let quote = self.bump()?;
        let mut lit = String::new();
        lit.push(quote);
        loop {
            let c = self.bump()?;
            lit.push(c);
            if c == '\\' {
                lit.push(self.bump()?);
            } else if c == quote {
                return Some(lit);
            }
        }
    }
}

/// Move accumulated literal text into a leaf node.
fn flush_text(text: &mut String, nodes: &mut Vec<DebugNode>) {
    if !text.is_empty() {
        nodes.push(DebugNode::Leaf(std::mem::take(text)));
    }
}

/// Split the atom glued to an open delimiter off the accumulated text:
/// `Some` from `Some(`, and `Name` (dropping the joining space) from
/// `Name {`. Brace groups only take a prefix across that space — a brace
/// directly following text is not the derived-struct shape.
fn take_group_prefix(text: &mut String, delimiter: char) -> String {
    if delimiter == '{' {
        let Some(without_space) = text.strip_suffix(' ') else {
            return String::new();
        };
        let start = without_space.rfind(' ').map(|index| index + 1).unwrap_or(0);
        let prefix = without_space[start..].to_string();
        if prefix.is_empty() {
            return String::new();
        }
        text.truncate(text.len() - prefix.len() - 1);
        prefix
    } else {
        let start = text.rfind(' ').map(|index| index + 1).unwrap_or(0);
        let prefix = text[start..].to_string();
        text.truncate(start);
        prefix
    }
}

/// Emit parsed nodes, matching the layout `#[derive(PrettyPrintable)]`
/// produces for the same shapes.
fn emit_debug_nodes(nodes: &[DebugNode], printer: &mut PrettyPrinter) {
    for node in nodes {
        match node {
            DebugNode::Leaf(text) => printer.text(text),
            DebugNode::Group {
                prefix,
                delimiter,
                named,
                items,
            } => {
                let (open, close, indent) = match (delimiter, named) {
                    ('{', true) => (format!("{prefix} {{"), " }", 4),
                    ('{', false) if prefix.is_empty() => ("{".to_string(), "}", 1),
                    ('{', false) => (format!("{prefix} {{"), "}", 1),
                    ('[', _) => (format!("{prefix}["), "]", 1),
                    _ => (format!("{prefix}("), ")", 1),
                };
                printer.begin_group(indent, &open);
                if *named {
                    printer.breakable(" ");
                }
                for (index, item) in items.iter().enumerate() {
                    if index > 0 {
                        printer.text(",");
                        printer.breakable(" ");
                    }
                    emit_debug_nodes(item, printer);
                }
                printer.end_group(close);
            }
        }
    }
}

/// A value that can describe its own printed representation.
///
/// Implementations should print the value in Rust-expression syntax wherever
/// possible, so a reported failing example can be pasted back into code, and
/// should express any internal structure through the printer's group and
/// breakable primitives so large values wrap readably.
///
/// Provided for the standard types the generator library produces. For user
/// types, either `#[derive(PrettyPrintable)]` or — to reuse an existing
/// `Debug` representation without writing anything —
/// [`pretty_print_as_debug!`](crate::pretty_print_as_debug).
///
/// `HashMap` and `HashSet` print as `HashMap::from([…])` /
/// `HashSet::from([…])`, expressions that only construct the default-hasher
/// types, so maps and sets with a custom hasher are deliberately not
/// printable — print those through
/// [`print_as_debug`](crate::generators::Generator::print_as_debug) or
/// [`print_with`](crate::generators::Generator::print_with) instead:
///
/// ```compile_fail,E0277
/// use std::collections::{HashMap, HashSet};
/// use std::hash::{BuildHasherDefault, DefaultHasher};
///
/// fn assert_printable<T: hegel::PrettyPrintable>() {}
/// assert_printable::<HashSet<i32, BuildHasherDefault<DefaultHasher>>>();
/// assert_printable::<HashMap<i32, bool, BuildHasherDefault<DefaultHasher>>>();
/// ```
#[diagnostic::on_unimplemented(
    message = "`{Self}` has no printed representation",
    label = "`{Self}` does not implement `PrettyPrintable`",
    note = "for your own type, add `#[derive(PrettyPrintable)]` (or `hegel::pretty_print_as_debug!` for a `Debug` type)",
    note = "for a foreign type, make the generator printable instead: `.print_as_debug()` prints any `Debug` value, `.print_with(..)` prints a custom representation",
    note = "or draw without reporting the value via `tc.draw_silent(..)`"
)]
pub trait PrettyPrintable {
    /// Print this value's representation to `printer`.
    fn pretty_print(&self, printer: &mut PrettyPrinter);
}

/// Implement [`PrettyPrintable`] for one or more local `Debug` types by
/// printing their `{:?}` representation through
/// [`print_debug_repr`](crate::pretty::print_debug_repr), so derived-`Debug`
/// output wraps like a native implementation.
///
/// This is for **your own types** whose `Debug` output is already the
/// representation you want: the orphan rule means it cannot implement a
/// hegel trait for a type from another crate (including the standard
/// library). To print a foreign type by its `Debug` representation, make
/// the *generator* printable instead with
/// [`print_as_debug`](crate::Generator::print_as_debug).
///
/// ```
/// use hegel::{Document, PrettyPrintable};
///
/// #[derive(Debug)]
/// struct Point {
///     x: i32,
///     y: i32,
/// }
/// hegel::pretty_print_as_debug!(Point);
///
/// let mut doc = Document::new();
/// Point { x: 1, y: 2 }.pretty_print(doc.printer());
/// assert_eq!(doc.finish(), "Point { x: 1, y: 2 }");
/// ```
#[macro_export]
macro_rules! pretty_print_as_debug {
    ($($t:ty),+ $(,)?) => {$(
        impl $crate::PrettyPrintable for $t {
            fn pretty_print(&self, printer: &mut $crate::PrettyPrinter) {
                $crate::pretty::print_debug_repr(&::std::format!("{:?}", self), printer);
            }
        }
    )+};
}

macro_rules! pretty_via_display {
    ($($t:ty),+) => {$(
        impl PrettyPrintable for $t {
            fn pretty_print(&self, printer: &mut PrettyPrinter) {
                printer.text(&format!("{}", self));
            }
        }
    )+};
}

pretty_via_display!(
    i8, i16, i32, i64, i128, isize, u8, u16, u32, u64, u128, usize, bool
);

macro_rules! pretty_via_debug {
    ($($t:ty),+) => {$(
        impl PrettyPrintable for $t {
            fn pretty_print(&self, printer: &mut PrettyPrinter) {
                printer.text(&format!("{:?}", self));
            }
        }
    )+};
}

pretty_via_debug!(char, str);

impl PrettyPrintable for String {
    fn pretty_print(&self, printer: &mut PrettyPrinter) {
        printer.text(&format!("{self:?}.to_string()"));
    }
}

impl PrettyPrintable for std::time::Duration {
    fn pretty_print(&self, printer: &mut PrettyPrinter) {
        printer.text(&format!(
            "Duration::new({}, {})",
            self.as_secs(),
            self.subsec_nanos()
        ));
    }
}

impl PrettyPrintable for std::net::Ipv4Addr {
    fn pretty_print(&self, printer: &mut PrettyPrinter) {
        let [a, b, c, d] = self.octets();
        printer.text(&format!("Ipv4Addr::new({a}, {b}, {c}, {d})"));
    }
}

impl PrettyPrintable for std::net::Ipv6Addr {
    fn pretty_print(&self, printer: &mut PrettyPrinter) {
        let segments = self
            .segments()
            .map(|segment| format!("{segment:#x}"))
            .join(", ");
        printer.text(&format!("Ipv6Addr::new({segments})"));
    }
}

impl PrettyPrintable for std::net::IpAddr {
    fn pretty_print(&self, printer: &mut PrettyPrinter) {
        match self {
            std::net::IpAddr::V4(addr) => {
                printer.text("IpAddr::V4(");
                addr.pretty_print(printer);
                printer.text(")");
            }
            std::net::IpAddr::V6(addr) => {
                printer.text("IpAddr::V6(");
                addr.pretty_print(printer);
                printer.text(")");
            }
        }
    }
}

macro_rules! pretty_float {
    ($t:ty, $name:literal) => {
        impl PrettyPrintable for $t {
            fn pretty_print(&self, printer: &mut PrettyPrinter) {
                if self.is_nan() {
                    if self.to_bits() == <$t>::NAN.to_bits() {
                        printer.text(concat!($name, "::NAN"));
                    } else {
                        printer.text(&format!(
                            concat!($name, "::from_bits(0x{:x})"),
                            self.to_bits()
                        ));
                    }
                } else if *self == <$t>::INFINITY {
                    printer.text(concat!($name, "::INFINITY"));
                } else if *self == <$t>::NEG_INFINITY {
                    printer.text(concat!($name, "::NEG_INFINITY"));
                } else {
                    printer.text(&format!("{:?}", self));
                }
            }
        }
    };
}

pretty_float!(f32, "f32");
pretty_float!(f64, "f64");

macro_rules! pretty_delegating {
    ($($t:ty),+) => {$(
        impl<T: PrettyPrintable + ?Sized> PrettyPrintable for $t {
            fn pretty_print(&self, printer: &mut PrettyPrinter) {
                (**self).pretty_print(printer);
            }
        }
    )+};
}

pretty_delegating!(&T, &mut T);

macro_rules! pretty_smart_pointer {
    ($($t:ty, $open:literal);+) => {$(
        impl<T: PrettyPrintable> PrettyPrintable for $t {
            fn pretty_print(&self, printer: &mut PrettyPrinter) {
                printer.begin_group($open.len(), $open);
                (**self).pretty_print(printer);
                printer.end_group(")");
            }
        }
    )+};
}

pretty_smart_pointer!(
    Box<T>, "Box::new(";
    std::rc::Rc<T>, "Rc::new(";
    std::sync::Arc<T>, "Arc::new("
);

/// `Box::new` cannot build a boxed unsized value, so `Box<str>` prints its
/// target instead of a constructor.
impl PrettyPrintable for Box<str> {
    fn pretty_print(&self, printer: &mut PrettyPrinter) {
        (**self).pretty_print(printer);
    }
}

/// Print `items` as a delimited, comma-separated sequence: inline when it
/// fits, one element per line (aligned just inside `open`) when it does not.
fn pretty_seq<'a, T: PrettyPrintable + ?Sized + 'a>(
    printer: &mut PrettyPrinter,
    open: &str,
    close: &str,
    items: impl Iterator<Item = &'a T>,
) {
    printer.begin_group(open.chars().count(), open);
    for (index, item) in items.enumerate() {
        if index > 0 {
            printer.text(",");
            printer.breakable(" ");
        }
        item.pretty_print(printer);
    }
    printer.end_group(close);
}

impl<T: PrettyPrintable> PrettyPrintable for [T] {
    fn pretty_print(&self, printer: &mut PrettyPrinter) {
        pretty_seq(printer, "[", "]", self.iter());
    }
}

impl<T: PrettyPrintable> PrettyPrintable for Vec<T> {
    fn pretty_print(&self, printer: &mut PrettyPrinter) {
        pretty_seq(printer, "vec![", "]", self.iter());
    }
}

impl<T: PrettyPrintable, const N: usize> PrettyPrintable for [T; N] {
    fn pretty_print(&self, printer: &mut PrettyPrinter) {
        self.as_slice().pretty_print(printer);
    }
}

impl<T: PrettyPrintable> PrettyPrintable for std::collections::HashSet<T> {
    fn pretty_print(&self, printer: &mut PrettyPrinter) {
        pretty_seq(printer, "HashSet::from([", "])", self.iter());
    }
}

impl<T: PrettyPrintable> PrettyPrintable for std::collections::BTreeSet<T> {
    fn pretty_print(&self, printer: &mut PrettyPrinter) {
        pretty_seq(printer, "BTreeSet::from([", "])", self.iter());
    }
}

/// Print `entries` as a `Name::from([(key, value), …])` map: inline when it
/// fits, one entry per line when it does not.
fn pretty_map<'a, K: PrettyPrintable + 'a, V: PrettyPrintable + 'a>(
    printer: &mut PrettyPrinter,
    open: &str,
    entries: impl Iterator<Item = (&'a K, &'a V)>,
) {
    printer.begin_group(open.chars().count(), open);
    for (index, (key, value)) in entries.enumerate() {
        if index > 0 {
            printer.text(",");
            printer.breakable(" ");
        }
        printer.text("(");
        key.pretty_print(printer);
        printer.text(", ");
        value.pretty_print(printer);
        printer.text(")");
    }
    printer.end_group("])");
}

impl<K: PrettyPrintable, V: PrettyPrintable> PrettyPrintable for std::collections::HashMap<K, V> {
    fn pretty_print(&self, printer: &mut PrettyPrinter) {
        pretty_map(printer, "HashMap::from([", self.iter());
    }
}

impl<K: PrettyPrintable, V: PrettyPrintable> PrettyPrintable for std::collections::BTreeMap<K, V> {
    fn pretty_print(&self, printer: &mut PrettyPrinter) {
        pretty_map(printer, "BTreeMap::from([", self.iter());
    }
}

impl<T: PrettyPrintable> PrettyPrintable for Option<T> {
    fn pretty_print(&self, printer: &mut PrettyPrinter) {
        match self {
            None => printer.text("None"),
            Some(value) => {
                printer.begin_group(5, "Some(");
                value.pretty_print(printer);
                printer.end_group(")");
            }
        }
    }
}

impl<T: PrettyPrintable, E: PrettyPrintable> PrettyPrintable for Result<T, E> {
    fn pretty_print(&self, printer: &mut PrettyPrinter) {
        match self {
            Ok(value) => {
                printer.begin_group(3, "Ok(");
                value.pretty_print(printer);
                printer.end_group(")");
            }
            Err(error) => {
                printer.begin_group(4, "Err(");
                error.pretty_print(printer);
                printer.end_group(")");
            }
        }
    }
}

impl PrettyPrintable for () {
    fn pretty_print(&self, printer: &mut PrettyPrinter) {
        printer.text("()");
    }
}

impl<A: PrettyPrintable> PrettyPrintable for (A,) {
    fn pretty_print(&self, printer: &mut PrettyPrinter) {
        printer.begin_group(1, "(");
        self.0.pretty_print(printer);
        printer.end_group(",)");
    }
}

macro_rules! pretty_tuple {
    ($(($($name:ident),+)),+ $(,)?) => {$(
        #[allow(non_snake_case)]
        impl<$($name: PrettyPrintable),+> PrettyPrintable for ($($name,)+) {
            fn pretty_print(&self, printer: &mut PrettyPrinter) {
                let ($($name,)+) = self;
                printer.begin_group(1, "(");
                let mut index = 0usize;
                $(
                    if index > 0 {
                        printer.text(",");
                        printer.breakable(" ");
                    }
                    index += 1;
                    $name.pretty_print(printer);
                )+
                let _ = index;
                printer.end_group(")");
            }
        }
    )+};
}

pretty_tuple!(
    (A, B),
    (A, B, C),
    (A, B, C, D),
    (A, B, C, D, E),
    (A, B, C, D, E, F),
    (A, B, C, D, E, F, G),
    (A, B, C, D, E, F, G, H),
    (A, B, C, D, E, F, G, H, I),
    (A, B, C, D, E, F, G, H, I, J),
    (A, B, C, D, E, F, G, H, I, J, K),
    (A, B, C, D, E, F, G, H, I, J, K, L),
);