dbc_codegen/

lib.rs

#![deny(missing_docs)]
#![deny(clippy::arithmetic_side_effects)]
#![allow(clippy::needless_doctest_main)]
#![cfg_attr(feature = "std", doc = include_str!("../README.md"))]
#![cfg_attr(
    not(feature = "std"),
    doc = "Documentation is only available with the `std` feature."
)]

mod feature_config;
mod keywords;
mod pad;
mod signal_type;
mod utils;

use std::collections::{BTreeMap, BTreeSet, HashMap};
use std::fs::OpenOptions;
use std::io::{BufWriter, Write};
use std::path::Path;

use anyhow::{Context, Error, Result, anyhow, ensure};
use can_dbc::ByteOrder::{BigEndian, LittleEndian};
use can_dbc::MultiplexIndicator::{
    MultiplexedSignal, Multiplexor, MultiplexorAndMultiplexedSignal, Plain,
};
use can_dbc::ValueType::Signed;
use can_dbc::{
    AttributeValue, AttributeValueForRelationType, Dbc, Message, MessageId, Signal, ValDescription,
    ValueDescription,
};
use heck::ToSnakeCase;
use quote::ToTokens;
use typed_builder::TypedBuilder;

pub use crate::feature_config::FeatureConfig;
use crate::pad::PadAdapter;
use crate::signal_type::{IntSize, ValType};
use crate::utils::{
    MessageExt as _, SignalExt as _, enum_name, enum_variant_name, is_screaming_snake_case,
    is_valid_ident, is_valid_type_path, multiplex_enum_name, multiplexed_enum_variant_name,
    multiplexed_enum_variant_wrapper_name, node_field_name,
};

static ALLOW_DEADCODE: &str = "#[allow(dead_code)]";
static ALLOW_LINTS: &str = r"#[allow(
    clippy::absurd_extreme_comparisons,
    clippy::excessive_precision,
    clippy::manual_range_contains,
    clippy::unnecessary_cast,
    clippy::useless_conversion,
    unused_comparisons,
    unused_variables,
)]";

/// Code generator configuration. See module-level docs for an example.
#[derive(TypedBuilder)]
#[non_exhaustive]
pub struct Config<'a> {
    /// Name of the dbc-file. Used for generated docs only.
    pub dbc_name: &'a str,

    /// Content of a dbc-file as a UTF-8 string. Use [`can_dbc::decode_cp1252`] or other encodings if needed.
    pub dbc_content: &'a str,

    /// Optional: Print debug info to stdout while generating code. Default: `false`.
    #[builder(default)]
    pub debug_prints: bool,

    /// Optional: `impl Debug` for generated types. Default: `Never`.
    #[builder(default)]
    pub impl_debug: FeatureConfig<'a>,

    /// Optional: `impl defmt::Format` for generated types. Default: `Never`.
    #[builder(default)]
    pub impl_defmt: FeatureConfig<'a>,

    /// Optional: `impl Arbitrary` for generated types. Default: `Never`.
    #[builder(default)]
    pub impl_arbitrary: FeatureConfig<'a>,

    /// Optional: `impl Serialize` and `impl Deserialize` for generated types.. Default: `Never`.
    #[builder(default)]
    pub impl_serde: FeatureConfig<'a>,

    /// Optional: `impl core::error::Error` for the generated `CanError` type. Default: `Never`.
    #[builder(default)]
    pub impl_error: FeatureConfig<'a>,

    /// Optional: Generate `embedded_can::Frame` impl for each frame. Default: `Always`
    #[builder(default = FeatureConfig::Always)]
    pub impl_embedded_can_frame: FeatureConfig<'a>,

    /// Optional: Validate min and max values in generated signal setters. Default: `Always`
    #[builder(default = FeatureConfig::Always)]
    pub check_ranges: FeatureConfig<'a>,

    /// Optional: Allow dead code in the generated module. Default: `false`.
    #[builder(default)]
    pub allow_dead_code: bool,

    /// Optional: Padding bit value used; set all unused bits to 1 if true else to 0. Default: `false`.
    #[builder(default)]
    pub padding_bit_value: bool,

    /// Optional: User-defined structs populated from DBC attributes.
    /// These are emitted as associated constants in the generated message types.
    /// Default: empty.
    #[builder(default)]
    pub attribute_structs: &'a [AttributeStruct<'a>],
}

/// A user-defined struct that [`Config`] fills from DBC attributes and emits as an
/// associated constant in the generated message type.
#[derive(Debug, Clone)]
pub struct AttributeStruct<'a> {
    /// Fully-qualified path of the target Rust type.
    pub type_path: &'a str,

    /// Base name of the emitted associated constant.
    pub const_name: &'a str,

    /// Whether one constant is emitted per message or per matching signal.
    pub scope: AttributeScope,

    /// Only emit the constant when this attribute has an assigned value on the
    /// scoped object (the message for [`AttributeScope::Message`] or the signal
    /// for [`AttributeScope::Signal`]).
    pub require: &'a str,

    /// The struct fields, written in this order.
    pub fields: &'a [AttributeField<'a>],

    /// Restrict [`AttributeScope::NodeSignal`]/[`AttributeScope::NodeMessage`]
    /// emission to this one node and remove the node name from the generated
    /// const. Set to `None` to keep the default behavior (one constant per
    /// matching node).
    pub for_node: Option<&'a str>,
}

/// Whether an [`AttributeStruct`] is emitted once per message or once per signal.
#[derive(Debug, Clone, Copy)]
#[non_exhaustive]
pub enum AttributeScope {
    /// One const per message (`BO_` attribute).
    Message,
    /// One const per signal (`SG_` attribute).
    Signal,
    /// One const per node related to a message (`BU_BO_REL_` relation attribute).
    NodeMessage,
    /// One const per receiving node of a signal (`BU_SG_REL_` relation attribute).
    NodeSignal,
}

/// One field of an [`AttributeStruct`] and where its value comes from.
#[derive(Debug, Clone)]
pub struct AttributeField<'a> {
    /// The target struct field name.
    pub name: &'a str,
    /// Where the field's value comes from.
    pub source: FieldSource<'a>,
}

/// Source of a generated [`AttributeField`] value.
#[derive(Debug, Clone)]
#[non_exhaustive]
pub enum FieldSource<'a> {
    /// Value of an attribute on the scoped object: a signal-level attribute in
    /// [`AttributeScope::Signal`] or a message-level attribute in
    /// [`AttributeScope::Message`].
    Attr(&'a str),
    /// Value of a message-level attribute.
    MessageAttr(&'a str),
    /// The signal's raw DBC start bit. [`AttributeScope::Signal`] only.
    StartBit,
    /// The signal's start byte. [`AttributeScope::Signal`] only.
    StartByte,
    /// The signal's width in bits. [`AttributeScope::Signal`] only.
    BitWidth,
    /// The message size in bytes.
    MessageSize,
    /// A literal integer.
    Int(i64),
    /// A literal string.
    Str(&'a str),
    /// The name of the related node.
    /// [`AttributeScope::NodeSignal`] and [`AttributeScope::NodeMessage`] only.
    NodeName,
}

/// Message/signal/node context used to resolve an [`AttributeStruct`]'s fields.
struct AttrTarget<'a> {
    msg: &'a Message,
    dbc: &'a Dbc,
    signal: Option<&'a Signal>,
    node: Option<&'a str>,
}

impl Config<'_> {
    /// Write Rust structs matching DBC input description to `out` buffer
    fn codegen(&self, out: impl Write) -> Result<()> {
        self.validate_attribute_structs()?;
        let dbc = Dbc::try_from(self.dbc_content).map_err(|e| {
            let msg = "Could not parse dbc file";
            if self.debug_prints {
                anyhow!("{msg}: {e:#?}")
            } else {
                anyhow!("{msg}")
            }
        })?;
        if self.debug_prints {
            eprintln!("{dbc:#?}");
        }
        let mut w = BufWriter::new(out);

        writeln!(
            w,
            "/// The name of the DBC file this code was generated from"
        )?;
        writeln!(w, "#[allow(dead_code)]")?;
        let dbc_name = self.dbc_name.to_token_stream();
        writeln!(w, "pub const DBC_FILE_NAME: &str = {dbc_name};")?;
        writeln!(
            w,
            "/// The version of the DBC file this code was generated from"
        )?;
        writeln!(w, "#[allow(dead_code)]")?;
        let dbc_version = dbc.version.0.to_token_stream();
        writeln!(w, "pub const DBC_FILE_VERSION: &str = {dbc_version};")?;

        writeln!(w, "#[allow(unused_imports)]")?;
        writeln!(w, "use core::ops::BitOr;")?;
        writeln!(w, "#[allow(unused_imports)]")?;
        writeln!(w, "use bitvec::prelude::*;")?;
        writeln!(w, "#[allow(unused_imports)]")?;
        writeln!(w, "use embedded_can::{{Id, StandardId, ExtendedId}};")?;

        self.impl_arbitrary.fmt_cfg(&mut w, |w| {
            writeln!(w, "use arbitrary::{{Arbitrary, Unstructured}};")
        })?;

        self.impl_serde.fmt_cfg(&mut w, |w| {
            writeln!(w, "use serde::{{Serialize, Deserialize}};")
        })?;

        writeln!(w)?;
        self.render_dbc(&mut w, &dbc)?;
        writeln!(w)?;
        self.render_error(&mut w)?;
        self.render_arbitrary_helpers(&mut w)?;
        writeln!(w)?;

        Ok(())
    }

    fn render_dbc(&self, w: &mut impl Write, dbc: &Dbc) -> Result<()> {
        self.render_root_enum(w, dbc)?;

        for msg in get_relevant_messages(dbc) {
            self.render_message(w, msg, dbc)
                .with_context(|| format!("write message `{}`", msg.name))?;
            writeln!(w)?;
        }

        Ok(())
    }

    fn render_root_enum(&self, w: &mut impl Write, dbc: &Dbc) -> Result<()> {
        writeln!(w, "/// All messages")?;
        writeln!(w, "{ALLOW_LINTS}")?;
        self.write_allow_dead_code(w)?;
        writeln!(w, "#[derive(Clone)]")?;
        self.impl_debug.fmt_attr(w, "derive(Debug)")?;
        self.impl_defmt.fmt_attr(w, "derive(defmt::Format)")?;
        self.impl_serde.fmt_attr(w, "derive(Serialize)")?;
        self.impl_serde.fmt_attr(w, "derive(Deserialize)")?;
        writeln!(w, "pub enum Messages {{")?;
        {
            let mut w = PadAdapter::wrap(w);
            for msg in get_relevant_messages(dbc) {
                writeln!(w, "/// {}", msg.name)?;
                writeln!(w, "{0}({0}),", msg.type_name())?;
            }
        }
        writeln!(w, "}}")?;
        writeln!(w)?;

        writeln!(w, "{ALLOW_LINTS}")?;
        self.write_allow_dead_code(w)?;
        writeln!(w, "impl Messages {{")?;
        {
            let mut w = PadAdapter::wrap(w);
            writeln!(w, "/// Read message from CAN frame")?;
            writeln!(w, "#[inline(never)]")?;
            writeln!(
                w,
                "pub fn from_can_message(id: Id, payload: &[u8]) -> Result<Self, CanError> {{",
            )?;

            {
                let mut w = PadAdapter::wrap(&mut w);
                let messages: Vec<_> = get_relevant_messages(dbc).collect();
                if messages.is_empty() {
                    writeln!(w, "Err(CanError::UnknownMessageId(id))")?;
                } else {
                    writeln!(w)?;
                    writeln!(w, "let res = match id {{")?;
                    {
                        let mut w = PadAdapter::wrap(&mut w);
                        for msg in messages {
                            writeln!(
                                w,
                                "{0}::MESSAGE_ID => Messages::{0}({0}::try_from(payload)?),",
                                msg.type_name(),
                            )?;
                        }
                        writeln!(w, r"id => return Err(CanError::UnknownMessageId(id)),")?;
                    }
                    writeln!(w, "}};")?;
                    writeln!(w, "Ok(res)")?;
                }
            }

            writeln!(w, "}}")?;
        }
        writeln!(w, "}}")?;
        writeln!(w)?;

        Ok(())
    }

    fn render_message(&self, w: &mut impl Write, msg: &Message, dbc: &Dbc) -> Result<()> {
        writeln!(w, "/// {}", msg.name)?;
        writeln!(w, "///")?;
        match msg.id {
            MessageId::Standard(id) => writeln!(w, "/// - Standard ID: {id} (0x{id:x})"),
            MessageId::Extended(id) => writeln!(w, "/// - Extended ID: {id} (0x{id:x})"),
        }?;
        writeln!(w, "/// - Size: {} bytes", msg.size)?;
        if let Some(transmitter) = &msg.transmitter {
            writeln!(w, "/// - Transmitter: {transmitter}")?;
        }
        if let Some(comment) = dbc.message_comment(msg.id) {
            writeln!(w, "///")?;
            for line in comment.trim().lines() {
                writeln!(w, "/// {line}")?;
            }
        }
        writeln!(w, "#[derive(Clone, Copy)]")?;
        self.impl_serde.fmt_attr(w, "derive(Serialize)")?;
        self.impl_serde.fmt_attr(w, "derive(Deserialize)")?;
        writeln!(w, "pub struct {} {{", msg.type_name())?;
        {
            let mut w = PadAdapter::wrap(w);
            self.impl_serde
                .fmt_attr(&mut w, "serde(with = \"serde_bytes\")")?;
            writeln!(w, "raw: [u8; {}],", msg.size)?;
        }
        writeln!(w, "}}")?;
        writeln!(w)?;

        writeln!(w, "{ALLOW_LINTS}")?;
        self.write_allow_dead_code(w)?;
        writeln!(w, "impl {} {{", msg.type_name())?;
        {
            let mut w = PadAdapter::wrap(w);

            writeln!(
                w,
                "pub const MESSAGE_ID: embedded_can::Id = {};",
                match msg.id {
                    MessageId::Standard(id) =>
                        format!("Id::Standard(StandardId::new({id:#x}).unwrap())"),
                    MessageId::Extended(id) =>
                        format!("Id::Extended(ExtendedId::new({id:#x}).unwrap())"),
                }
            )?;
            writeln!(w)?;

            writeln!(w, "pub const MESSAGE_SIZE: usize = {};", msg.size)?;
            writeln!(w)?;

            Self::render_cycle_time(&mut w, msg, dbc)?;

            for signal in &msg.signals {
                let typ = ValType::from_signal(signal);
                if typ != ValType::Bool {
                    let sig = signal.field_name().to_uppercase();
                    let min = signal.min;
                    let max = signal.max;
                    writeln!(w, "pub const {sig}_MIN: {typ} = {min}_{typ};")?;
                    writeln!(w, "pub const {sig}_MAX: {typ} = {max}_{typ};")?;
                }
            }
            writeln!(w)?;

            self.render_attribute_structs(&mut w, msg, dbc)?;

            writeln!(
                w,
                "/// Constructs a new `{}` message from values.",
                msg.name
            )?;
            let args = msg
                .signals
                .iter()
                .filter_map(|signal| {
                    if matches!(signal.multiplexer_indicator, Plain | Multiplexor) {
                        let field = signal.field_name();
                        let typ = signal_pub_type(dbc, msg, signal);
                        Some(format!("{field}: {typ}"))
                    } else {
                        None
                    }
                })
                .collect::<Vec<_>>()
                .join(", ");
            writeln!(w, "pub fn new({args}) -> Result<Self, CanError> {{")?;
            {
                let mut w = PadAdapter::wrap(&mut w);
                let mutable = if msg.signals.is_empty() { "" } else { "mut " };
                let padding_value = if self.padding_bit_value {
                    "0xFF"
                } else {
                    "0x00"
                };
                let size = msg.size;
                writeln!(
                    w,
                    "let {mutable}res = Self {{ raw: [{padding_value}; {size}] }};"
                )?;
                for signal in &msg.signals {
                    if matches!(signal.multiplexer_indicator, Plain | Multiplexor) {
                        writeln!(w, "res.set_{0}({0})?;", signal.field_name())?;
                    }
                }
                writeln!(w, "Ok(res)")?;
            }
            writeln!(w, "}}")?;
            writeln!(w)?;

            writeln!(w, "/// Returns the raw `{}` message payload.", msg.name)?;
            writeln!(w, "pub fn raw(&self) -> &[u8; {}] {{", msg.size)?;
            {
                let mut w = PadAdapter::wrap(&mut w);
                writeln!(w, "&self.raw")?;
            }
            writeln!(w, "}}")?;
            writeln!(w)?;

            for signal in &msg.signals {
                match signal.multiplexer_indicator {
                    Plain => self
                        .render_signal(&mut w, signal, dbc, msg)
                        .with_context(|| format!("write signal impl `{}`", signal.name))?,
                    Multiplexor => {
                        self.render_multiplexor_signal(&mut w, signal, dbc, msg)?;
                    }
                    MultiplexedSignal(_) | MultiplexorAndMultiplexedSignal(_) => {}
                }
            }
        }

        writeln!(w, "}}")?;
        writeln!(w)?;

        let typ = msg.type_name();
        writeln!(w, "impl core::convert::TryFrom<&[u8]> for {typ} {{")?;
        {
            let mut w = PadAdapter::wrap(w);
            writeln!(w, "type Error = CanError;")?;
            writeln!(w)?;
            writeln!(w, "#[inline(always)]")?;
            writeln!(
                w,
                "fn try_from(payload: &[u8]) -> Result<Self, Self::Error> {{",
            )?;
            {
                let mut w = PadAdapter::wrap(&mut w);
                writeln!(
                    w,
                    r"if payload.len() != {} {{ return Err(CanError::InvalidPayloadSize); }}",
                    msg.size,
                )?;
                writeln!(w, "let mut raw = [0u8; {}];", msg.size)?;
                writeln!(w, "raw.copy_from_slice(&payload[..{}]);", msg.size)?;
                writeln!(w, "Ok(Self {{ raw }})")?;
            }
            writeln!(w, "}}")?;
        }
        writeln!(w, "}}")?;
        writeln!(w)?;

        self.render_embedded_can_frame(w, msg)?;

        self.impl_debug
            .fmt_cfg(&mut *w, |w| render_debug_impl(w, msg))?;
        self.impl_defmt
            .fmt_cfg(&mut *w, |w| render_defmt_impl(w, msg))?;
        self.impl_arbitrary
            .fmt_cfg(&mut *w, |w| self.render_arbitrary(w, dbc, msg))?;

        let enums_for_this_message = dbc.value_descriptions.iter().filter_map(|x| {
            if let ValueDescription::Signal {
                message_id,
                name,
                value_descriptions,
            } = x
            {
                if *message_id != msg.id {
                    return None;
                }
                dbc.signal_by_name(*message_id, name)
                    .map(|v| (v, value_descriptions))
            } else {
                None
            }
        });
        for (signal, variants) in enums_for_this_message {
            self.write_enum(w, signal, msg, variants.as_slice())?;
        }

        let multiplexor_signal = msg
            .signals
            .iter()
            .find(|s| s.multiplexer_indicator == Multiplexor);

        if let Some(multiplexor_signal) = multiplexor_signal {
            self.render_multiplexor_enums(w, dbc, msg, multiplexor_signal)?;
        }

        Ok(())
    }

    /// Validate the [`AttributeStruct`] specs.
    fn validate_attribute_structs(&self) -> Result<()> {
        for spec in self.attribute_structs {
            // Require SCREAMING_SNAKE_CASE to guarantee that the name never collides
            // with a generated method (all `snake_case`).
            ensure!(
                is_screaming_snake_case(spec.const_name),
                "attribute_structs: 'const_name' {:?} must be SCREAMING_SNAKE_CASE",
                spec.const_name
            );
            ensure!(
                is_valid_type_path(spec.type_path),
                "attribute_structs: 'type_path' {:?} for {:?} is not a valid Rust type path",
                spec.type_path,
                spec.const_name
            );
            ensure!(
                !spec.require.is_empty(),
                "attribute_structs: 'require' must not be empty for {:?}",
                spec.const_name
            );
            ensure!(
                !spec.fields.is_empty(),
                "attribute_structs: {:?} declares no fields",
                spec.const_name
            );

            let has_signal = matches!(
                spec.scope,
                AttributeScope::Signal | AttributeScope::NodeSignal
            );
            let has_node = matches!(
                spec.scope,
                AttributeScope::NodeSignal | AttributeScope::NodeMessage
            );
            if let Some(for_node) = spec.for_node {
                ensure!(
                    !for_node.is_empty(),
                    "attribute_structs: 'for_node' must not be empty for {:?}",
                    spec.const_name
                );
                ensure!(
                    has_node,
                    "attribute_structs: {:?} sets 'for_node' but its scope has no associated \
                     node (scope must be NodeSignal or NodeMessage)",
                    spec.const_name
                );
            }
            let mut seen = BTreeSet::new();
            for field in spec.fields {
                ensure!(
                    is_valid_ident(field.name),
                    "attribute_structs: field name {:?} in {:?} is not a valid Rust identifier",
                    field.name,
                    spec.const_name
                );
                ensure!(
                    seen.insert(field.name),
                    "attribute_structs: duplicate field {:?} in {:?}",
                    field.name,
                    spec.const_name
                );
                if !has_signal {
                    ensure!(
                        !matches!(
                            field.source,
                            FieldSource::StartBit | FieldSource::StartByte | FieldSource::BitWidth
                        ),
                        "attribute_structs: field {:?} of {:?} uses a signal-only source \
                         (StartBit/StartByte/BitWidth) but the struct has no associated signal",
                        field.name,
                        spec.const_name
                    );
                }
                if !has_node {
                    ensure!(
                        !matches!(field.source, FieldSource::NodeName),
                        "attribute_structs: field {:?} of {:?} uses NodeName but the struct has \
                         no associated node (scope must be NodeSignal or NodeMessage)",
                        field.name,
                        spec.const_name
                    );
                }
            }
        }
        Ok(())
    }

    /// Emit the configured [`AttributeStruct`]s as associated constants.
    fn render_attribute_structs(&self, w: &mut impl Write, msg: &Message, dbc: &Dbc) -> Result<()> {
        if self.attribute_structs.is_empty() {
            return Ok(());
        }

        // Track every associated item already emitted for this message type so
        // that colliding const names are rejected here instead of producing code
        // that fails to build. Using a BTree to ensure deterministic output.
        let mut used: BTreeSet<String> = BTreeSet::new();
        used.insert("MESSAGE_ID".to_string());
        for signal in &msg.signals {
            if ValType::from_signal(signal) != ValType::Bool {
                let sig = signal.field_name().to_uppercase();
                used.insert(format!("{sig}_MIN"));
                used.insert(format!("{sig}_MAX"));
            }
        }

        for spec in self.attribute_structs {
            match spec.scope {
                AttributeScope::Message => {
                    if dbc.message_attribute(msg.id, spec.require).is_none() {
                        continue;
                    }
                    Self::render_attribute_struct(
                        w,
                        spec,
                        spec.const_name,
                        &AttrTarget {
                            msg,
                            dbc,
                            signal: None,
                            node: None,
                        },
                        &mut used,
                    )?;
                }
                AttributeScope::Signal => {
                    for signal in &msg.signals {
                        if dbc
                            .signal_attribute(msg.id, &signal.name, spec.require)
                            .is_none()
                        {
                            continue;
                        }
                        let name =
                            format!("{}_{}", signal.field_name().to_uppercase(), spec.const_name);
                        Self::render_attribute_struct(
                            w,
                            spec,
                            &name,
                            &AttrTarget {
                                msg,
                                dbc,
                                signal: Some(signal),
                                node: None,
                            },
                            &mut used,
                        )?;
                    }
                }
                AttributeScope::NodeSignal => {
                    for signal in &msg.signals {
                        for node in &signal.receivers {
                            if spec.for_node.is_some_and(|target| node != target) {
                                continue;
                            }
                            if node_relation_attribute(
                                dbc,
                                node,
                                msg.id,
                                Some(&signal.name),
                                spec.require,
                            )
                            .is_none()
                            {
                                continue;
                            }
                            let name = if spec.for_node.is_some() {
                                format!(
                                    "{}_{}",
                                    signal.field_name().to_uppercase(),
                                    spec.const_name
                                )
                            } else {
                                let node_ident = node_field_name(node).to_uppercase();
                                format!(
                                    "{}_{node_ident}_{}",
                                    signal.field_name().to_uppercase(),
                                    spec.const_name
                                )
                            };
                            Self::render_attribute_struct(
                                w,
                                spec,
                                &name,
                                &AttrTarget {
                                    msg,
                                    dbc,
                                    signal: Some(signal),
                                    node: Some(node),
                                },
                                &mut used,
                            )?;
                        }
                    }
                }
                AttributeScope::NodeMessage => {
                    for node in &dbc.nodes {
                        if spec.for_node.is_some_and(|target| node.0 != target) {
                            continue;
                        }
                        if node_relation_attribute(dbc, &node.0, msg.id, None, spec.require)
                            .is_none()
                        {
                            continue;
                        }
                        let name = if spec.for_node.is_some() {
                            spec.const_name.to_string()
                        } else {
                            format!(
                                "{}_{}",
                                node_field_name(&node.0).to_uppercase(),
                                spec.const_name
                            )
                        };
                        Self::render_attribute_struct(
                            w,
                            spec,
                            &name,
                            &AttrTarget {
                                msg,
                                dbc,
                                signal: None,
                                node: Some(&node.0),
                            },
                            &mut used,
                        )?;
                    }
                }
            }
        }
        Ok(())
    }

    /// Emit a single struct constant.
    fn render_attribute_struct(
        w: &mut impl Write,
        spec: &AttributeStruct<'_>,
        const_name: &str,
        target: &AttrTarget<'_>,
        used: &mut BTreeSet<String>,
    ) -> Result<()> {
        ensure!(
            used.insert(const_name.to_string()),
            "attribute_structs: generated const '{const_name}' on message {:?} collides with \
             another const. Use a distinct 'const_name'.",
            target.msg.name
        );

        let mut fields = Vec::with_capacity(spec.fields.len());
        for field in spec.fields {
            let lit = resolve_field_source(&field.source, target).ok_or_else(|| {
                anyhow!(
                    "attribute_structs: const '{const_name}' field {:?} has no value in the DBC \
                     and no default (source: {:?})",
                    field.name,
                    field.source
                )
            })?;
            fields.push((field.name, lit));
        }

        let ty = spec.type_path;
        writeln!(w, "/// Generated from DBC attributes `{}`", spec.require)?;
        writeln!(w, "pub const {const_name}: {ty} = {ty} {{")?;
        {
            let mut w = PadAdapter::wrap(w);
            for (name, lit) in fields {
                writeln!(w, "{name}: {lit},")?;
            }
        }
        writeln!(w, "}};")?;
        writeln!(w)?;
        Ok(())
    }

    /// Emit the cycle time as a constant for messages that have an assigned
    /// `GenMsgCycleTime` (`BA_`) attribute.
    fn render_cycle_time(w: &mut impl Write, msg: &Message, dbc: &Dbc) -> Result<()> {
        let Some(ms) = message_cycle_time_ms(dbc, msg.id) else {
            return Ok(());
        };
        writeln!(w, "pub const MESSAGE_CYCLE_TIME_MS: u32 = {ms};")?;
        Ok(())
    }

    fn render_signal(
        &self,
        w: &mut impl Write,
        signal: &Signal,
        dbc: &Dbc,
        msg: &Message,
    ) -> Result<()> {
        writeln!(w, "/// Returns the value of `{}`.", signal.name)?;
        if let Some(comment) = dbc.signal_comment(msg.id, &signal.name) {
            writeln!(w, "///")?;
            for line in comment.trim().lines() {
                writeln!(w, "/// {line}")?;
            }
        }
        writeln!(w, "///")?;
        writeln!(w, "/// - Min: {}", signal.min)?;
        writeln!(w, "/// - Max: {}", signal.max)?;
        if signal.unit.is_empty() {
            writeln!(w, "/// - Unit: Not specified")?;
        } else {
            writeln!(w, "/// - Unit: {:?}", signal.unit)?;
        }
        if signal.receivers.is_empty() {
            writeln!(w, "/// - Receivers: Vector__XXX")?;
        } else {
            writeln!(w, "/// - Receivers: {}", signal.receivers.join(", "))?;
        }

        let fn_name = signal.field_name();
        let variants = dbc.value_descriptions_for_signal(msg.id, &signal.name);
        if variants.is_none() {
            writeln!(w, "/// - Factor: {}", signal.factor)?;
            writeln!(w, "/// - Offset: {}", signal.offset)?;
        }
        writeln!(w, "#[inline(always)]")?;
        if let Some(variants) = variants {
            let type_name = enum_name(msg, signal);
            let signal_ty = ValType::from_signal(signal);
            let variant_infos = generate_variant_info(variants, signal_ty);

            writeln!(w, "pub fn {fn_name}(&self) -> {type_name} {{")?;
            {
                let mut w = PadAdapter::wrap(w);

                // Use signed type for loading when signal is signed and has negative values
                let has_negative_values = variants.iter().any(|v| v.id < 0);
                let load_type = if signal.value_type == Signed && has_negative_values {
                    signal_ty
                } else {
                    ValType::from_signal_uint(signal)
                };

                let read = read_fn_with_type(signal, msg, load_type)?;
                writeln!(w, r"let signal = {read};")?;
                writeln!(w)?;
                writeln!(w, "match signal {{")?;
                {
                    let mut w = PadAdapter::wrap(&mut w);
                    for info in &variant_infos {
                        let literal = info.value;
                        let variant = &info.base_name;
                        match info.dup_type {
                            DuplicateType::Unique => {
                                writeln!(w, "{literal} => {type_name}::{variant},")?;
                            }
                            DuplicateType::FirstDuplicate | DuplicateType::Duplicate => {
                                writeln!(w, "{literal} => {type_name}::{variant}({literal}),")?;
                            }
                        }
                    }
                    writeln!(w, "_ => {type_name}::_Other(self.{fn_name}_phys_val()),")?;
                }
                writeln!(w, "}}")?;
            }
            writeln!(w, "}}")?;
            writeln!(w)?;

            // Private helper for the `_Other()` fallback above.
            writeln!(w, "#[inline(always)]")?;
            let typ = ValType::from_signal(signal);
            writeln!(w, "fn {fn_name}_phys_val(&self) -> {typ} {{")?;
            {
                let mut w = PadAdapter::wrap(w);
                signal_from_payload(&mut w, signal, msg).context("signal from payload")?;
            }
            writeln!(w, "}}")?;
            writeln!(w)?;
        } else {
            let typ = ValType::from_signal(signal);
            writeln!(w, "pub fn {fn_name}(&self) -> {typ} {{")?;
            {
                let mut w = PadAdapter::wrap(w);
                signal_from_payload(&mut w, signal, msg).context("signal from payload")?;
            }
            writeln!(w, "}}")?;
            writeln!(w)?;
        }

        render_raw_accessors(w, signal, msg)?;

        self.render_set_signal(w, signal, dbc, msg)?;

        Ok(())
    }

    fn render_set_signal(
        &self,
        w: &mut impl Write,
        signal: &Signal,
        dbc: &Dbc,
        msg: &Message,
    ) -> Result<()> {
        // To avoid accidentally changing the multiplexor value without changing
        // the signals accordingly this fn is kept private for multiplexors.
        let visibility = if signal.multiplexer_indicator == Multiplexor {
            ""
        } else {
            "pub "
        };

        let field = signal.field_name();
        let typ = ValType::from_signal(signal);
        let param_type = signal_pub_type(dbc, msg, signal);
        let is_enum_backed = param_type != typ.to_string();

        writeln!(w, "/// Sets the value of `{}`.", signal.name)?;
        writeln!(w, "#[inline(always)]")?;
        writeln!(
            w,
            "{visibility}fn set_{field}(&mut self, value: {param_type}) -> Result<(), CanError> {{",
        )?;
        {
            let mut w = PadAdapter::wrap(w);
            // Enum-backed signals accept the value-description enum; convert it to
            // the raw primitive before range checks and packing.
            if is_enum_backed {
                writeln!(w, "let value = {typ}::from(value);")?;
            }
            self.render_set_signal_body(&mut w, signal, msg)?;
        }
        writeln!(w, "}}")?;
        writeln!(w)?;

        Ok(())
    }

    fn render_set_signal_body(
        &self,
        w: &mut impl Write,
        signal: &Signal,
        msg: &Message,
    ) -> Result<()> {
        if signal.size != 1 {
            if let FeatureConfig::Gated(gate) = self.check_ranges {
                writeln!(w, r"#[cfg(feature = {gate:?})]")?;
            }

            if let FeatureConfig::Gated(..) | FeatureConfig::Always = self.check_ranges {
                let typ = ValType::from_signal(signal);
                let min = signal.min;
                let max = signal.max;
                writeln!(w, r"if value < {min}_{typ} || {max}_{typ} < value {{")?;

                {
                    let mut w = PadAdapter::wrap(&mut *w);
                    let typ = msg.type_name();
                    writeln!(
                        w,
                        r"return Err(CanError::ParameterOutOfRange {{ message_id: {typ}::MESSAGE_ID }});",
                    )?;
                }

                writeln!(w, r"}}")?;
            }
        }
        signal_to_payload(&mut *w, signal, msg).context("signal to payload")?;

        Ok(())
    }

    fn render_multiplexor_signal(
        &self,
        w: &mut impl Write,
        signal: &Signal,
        dbc: &Dbc,
        msg: &Message,
    ) -> Result<()> {
        let signal_typ = ValType::from_signal(signal);

        render_raw_accessors(w, signal, msg)?;

        let field = signal.field_name();
        let typ = multiplex_enum_name(msg, signal)?;
        writeln!(
            w,
            "/// Selects the active multiplexed sub-message for `{}`.",
            signal.name
        )?;
        writeln!(
            w,
            "pub fn {field}_multiplexed(&mut self) -> Result<{typ}, CanError> {{"
        )?;

        let multiplexer_indexes: BTreeSet<u64> = msg
            .signals
            .iter()
            .filter_map(|s| {
                if let MultiplexedSignal(index) = &s.multiplexer_indicator {
                    Some(index)
                } else {
                    None
                }
            })
            .copied()
            .collect();

        {
            let mut w = PadAdapter::wrap(w);
            writeln!(w, "match self.{}_raw_val() {{", signal.field_name())?;

            {
                let mut w = PadAdapter::wrap(&mut w);
                for idx in &multiplexer_indexes {
                    writeln!(
                        w,
                        "{idx} => Ok({enum_name}::{multiplexed_wrapper_name}({multiplexed_name}{{ raw: self.raw }})),",
                        enum_name = multiplex_enum_name(msg, signal)?,
                        multiplexed_wrapper_name = multiplexed_enum_variant_wrapper_name(*idx),
                        multiplexed_name = multiplexed_enum_variant_name(msg, signal, *idx)?,
                    )?;
                }
                let to_u16 = match signal_typ {
                    ValType::UnsignedInt(IntSize::Size8) => "multiplexor.into()",
                    ValType::UnsignedInt(IntSize::Size16) => "multiplexor",
                    _ => "u16::try_from(multiplexor).unwrap_or(u16::MAX)",
                };
                writeln!(
                    w,
                    "multiplexor => Err(CanError::InvalidMultiplexor {{ message_id: {}::MESSAGE_ID, multiplexor: {to_u16} }}),",
                    msg.type_name(),
                )?;
            }

            writeln!(w, "}}")?;
        }
        writeln!(w, "}}")?;

        self.render_set_signal(w, signal, dbc, msg)?;

        for switch_index in multiplexer_indexes {
            render_set_signal_multiplexer(w, signal, msg, switch_index)?;
        }

        Ok(())
    }

    fn write_enum(
        &self,
        w: &mut impl Write,
        signal: &Signal,
        msg: &Message,
        variants: &[ValDescription],
    ) -> Result<()> {
        let type_name = enum_name(msg, signal);
        let signal_ty = ValType::from_signal(signal);

        // Generate variant info to handle duplicates with tuple variants
        let variant_infos = generate_variant_info(variants, signal_ty);

        writeln!(w, "/// Defined values for {}", signal.name)?;
        writeln!(w, "{ALLOW_LINTS}")?;
        self.write_allow_dead_code(w)?;
        writeln!(w, "#[derive(Clone, Copy, PartialEq)]")?;
        self.impl_debug.fmt_attr(w, "derive(Debug)")?;
        self.impl_defmt.fmt_attr(w, "derive(defmt::Format)")?;
        self.impl_serde.fmt_attr(w, "derive(Serialize)")?;
        self.impl_serde.fmt_attr(w, "derive(Deserialize)")?;
        writeln!(w, "pub enum {type_name} {{")?;
        {
            let mut w = PadAdapter::wrap(w);
            for info in &variant_infos {
                let variant = &info.base_name;
                match info.dup_type {
                    DuplicateType::Unique => writeln!(w, "{variant},")?,
                    DuplicateType::FirstDuplicate => {
                        writeln!(w, "{variant}({}),", info.value_type)?;
                    }
                    DuplicateType::Duplicate => {}
                }
            }
            writeln!(w, "_Other({signal_ty}),")?;
        }
        writeln!(w, "}}")?;
        writeln!(w)?;

        writeln!(w, "impl From<{type_name}> for {signal_ty} {{")?;
        {
            let match_on_raw_type = match ValType::from_signal(signal) {
                ValType::Bool => |x: i64| format!("{}", x == 1),
                ValType::F32 => |x: i64| format!("{x}_f32"),
                _ => |x: i64| format!("{x}"),
            };

            let mut w = PadAdapter::wrap(w);
            writeln!(w, "fn from(val: {type_name}) -> {signal_ty} {{")?;
            {
                let mut w = PadAdapter::wrap(&mut w);
                writeln!(w, "match val {{")?;
                {
                    let mut w = PadAdapter::wrap(&mut w);
                    for info in &variant_infos {
                        match info.dup_type {
                            DuplicateType::Unique => {
                                let literal = match_on_raw_type(info.value);
                                writeln!(w, "{type_name}::{} => {literal},", info.base_name)?;
                            }
                            DuplicateType::FirstDuplicate => {
                                writeln!(w, "{type_name}::{}(v) => v,", info.base_name)?;
                            }
                            DuplicateType::Duplicate => {}
                        }
                    }
                    writeln!(w, "{type_name}::_Other(x) => x,")?;
                }
                writeln!(w, "}}")?;
            }
            writeln!(w, "}}")?;
        }
        writeln!(w, "}}")?;
        writeln!(w)?;
        Ok(())
    }
}

fn render_set_signal_multiplexer(
    w: &mut impl Write,
    multiplexor: &Signal,
    msg: &Message,
    switch_index: u64,
) -> Result<()> {
    writeln!(w, "/// Sets the value of `{}`.", multiplexor.name)?;
    writeln!(w, "#[inline(always)]")?;
    writeln!(
        w,
        "pub fn set_{enum_variant_wrapper}(&mut self, value: {enum_variant}) -> Result<(), CanError> {{",
        enum_variant_wrapper = multiplexed_enum_variant_wrapper_name(switch_index).to_snake_case(),
        enum_variant = multiplexed_enum_variant_name(msg, multiplexor, switch_index)?,
    )?;

    {
        let mut w = PadAdapter::wrap(w);

        writeln!(w, "let b0 = BitArray::<_, LocalBits>::new(self.raw);")?;
        writeln!(w, "let b1 = BitArray::<_, LocalBits>::new(value.raw);")?;
        writeln!(w, "self.raw = b0.bitor(b1).into_inner();")?;
        writeln!(w, "self.set_{}({switch_index})?;", multiplexor.field_name())?;
        writeln!(w, "Ok(())")?;
    }

    writeln!(w, "}}")?;
    writeln!(w)?;

    Ok(())
}

fn be_start_end_bit(signal: &Signal, msg: &Message) -> Result<(u64, u64)> {
    let err = "calculating start bit";

    let x = signal.start_bit.checked_div(8).context(err)?;
    let x = x.checked_mul(8).context(err)?;

    let y = signal.start_bit.checked_rem(8).context(err)?;
    let y = 7u64.checked_sub(y).context(err)?;

    let start_bit = x.checked_add(y).context(err)?;
    let end_bit = start_bit
        .checked_add(signal.size)
        .context("calculating last bit position")?;

    let msg_bits = msg.size.checked_mul(8).context("message size overflow")?;

    ensure!(
        start_bit <= msg_bits,
        "signal starts at {start_bit}, but message is only {msg_bits} bits",
    );
    ensure!(
        end_bit <= msg_bits,
        "signal ends at {end_bit}, but message is only {msg_bits} bits",
    );
    Ok((start_bit, end_bit))
}

fn le_start_end_bit(signal: &Signal, msg: &Message) -> Result<(u64, u64)> {
    let msg_bits = msg.size.checked_mul(8).context("message size overflow")?;
    let start_bit = signal.start_bit;
    ensure!(
        start_bit <= msg_bits,
        "signal starts at {start_bit}, but message is only {msg_bits} bits",
    );

    let end_bit = signal
        .start_bit
        .checked_add(signal.size)
        .context("overflow calculating last bit position")?;
    ensure!(
        end_bit <= msg_bits,
        "signal ends at {end_bit}, but message is only {msg_bits} bits",
    );
    Ok((start_bit, end_bit))
}

/// Public type of a signal as seen by `new()` and `set_*`. This is the
/// enum when the signal has one (and isn't the multiplexor selector), otherwise
/// it is the raw primitive type.
fn signal_pub_type(dbc: &Dbc, msg: &Message, signal: &Signal) -> String {
    if signal.multiplexer_indicator != Multiplexor
        && dbc
            .value_descriptions_for_signal(msg.id, &signal.name)
            .is_some()
    {
        enum_name(msg, signal)
    } else {
        ValType::from_signal(signal).to_string()
    }
}

/// Whether the signal has no scaling applied, i.e. its raw and physical values are identical.
/// The float comparison to exact values is intentional.
#[allow(clippy::float_cmp)]
fn is_unscaled(signal: &Signal) -> bool {
    signal.factor == 1.0 && signal.offset == 0.0
}

fn signal_from_payload(w: &mut impl Write, signal: &Signal, msg: &Message) -> Result<()> {
    if is_unscaled(signal) {
        let field = signal.field_name();
        if signal.size == 1 {
            writeln!(w, "self.{field}_raw_val() == 1")?;
        } else {
            writeln!(w, "self.{field}_raw_val()")?;
        }
        return Ok(());
    }

    writeln!(w, r"let signal = {};", read_fn(signal, msg)?)?;
    writeln!(w)?;

    let typ = ValType::from_signal(signal);
    match typ {
        ValType::Bool => {
            writeln!(w, "signal == 1")?;
        }
        ValType::F32 => {
            // Scaling is always done on floats
            writeln!(w, "let factor = {}_f32;", signal.factor)?;
            writeln!(w, "let offset = {}_f32;", signal.offset)?;
            writeln!(w, "(signal as f32) * factor + offset")?;
        }
        _ => {
            writeln!(w, "let factor = {};", signal.factor)?;
            if Some(typ) == ValType::from_signal_uint(signal).unsigned_to_signed() {
                // Can't do iNN::from(uNN) if they both fit in the same integer type,
                // so cast first
                writeln!(w, "let signal = signal as {typ};")?;
            }

            if signal.offset >= 0.0 {
                writeln!(
                    w,
                    "{typ}::from(signal).saturating_mul(factor).saturating_add({})",
                    signal.offset,
                )?;
            } else {
                writeln!(
                    w,
                    "{typ}::from(signal).saturating_mul(factor).saturating_sub({})",
                    signal.offset.abs(),
                )?;
            }
        }
    }
    Ok(())
}

fn read_fn(signal: &Signal, msg: &Message) -> Result<String> {
    read_fn_with_type(signal, msg, ValType::from_signal_int(signal))
}

fn read_fn_with_type(signal: &Signal, msg: &Message, typ: ValType) -> Result<String> {
    Ok(match signal.byte_order {
        LittleEndian => {
            let (start, end) = le_start_end_bit(signal, msg)?;
            format!("self.raw.view_bits::<Lsb0>()[{start}..{end}].load_le::<{typ}>()")
        }
        BigEndian => {
            let (start, end) = be_start_end_bit(signal, msg)?;
            format!("self.raw.view_bits::<Msb0>()[{start}..{end}].load_be::<{typ}>()")
        }
    })
}

fn signal_to_payload(w: &mut impl Write, signal: &Signal, msg: &Message) -> Result<()> {
    let typ = ValType::from_signal(signal);
    match typ {
        ValType::Bool => {
            // Map boolean to byte so we can pack it
            writeln!(w, "let value = value as u8;")?;
        }
        ValType::F32 => {
            // Massage value into an int
            writeln!(w, "let factor = {}_f32;", signal.factor)?;
            writeln!(w, "let offset = {}_f32;", signal.offset)?;
            let typ = ValType::from_signal_int(signal);
            writeln!(w, "let value = ((value - offset) / factor) as {typ};")?;
            writeln!(w)?;
        }
        _ if is_unscaled(signal) => {
            // `value` is already the raw type.
        }
        _ => {
            writeln!(w, "let factor = {};", signal.factor)?;
            if signal.offset >= 0.0 {
                writeln!(w, "let value = value.checked_sub({})", signal.offset)?;
            } else {
                writeln!(w, "let value = value.checked_add({})", signal.offset.abs())?;
            }
            writeln!(
                w,
                "    .ok_or(CanError::ParameterOutOfRange {{ message_id: {}::MESSAGE_ID }})?;",
                msg.type_name(),
            )?;
            let typ = ValType::from_signal_int(signal);
            writeln!(w, "let value = (value / factor) as {typ};")?;
            writeln!(w)?;
        }
    }

    pack_bits(w, signal, msg)?;

    writeln!(w, "Ok(())")?;
    Ok(())
}

/// Pack `value` into the message payload.
fn pack_bits(w: &mut impl Write, signal: &Signal, msg: &Message) -> Result<()> {
    if signal.value_type == Signed {
        let typ = ValType::from_signal_uint(signal);
        writeln!(w, "let value = {typ}::from_ne_bytes(value.to_ne_bytes());")?;
    }

    match signal.byte_order {
        LittleEndian => {
            let (start, end) = le_start_end_bit(signal, msg)?;
            writeln!(
                w,
                r"self.raw.view_bits_mut::<Lsb0>()[{start}..{end}].store_le(value);",
            )?;
        }
        BigEndian => {
            let (start, end) = be_start_end_bit(signal, msg)?;
            writeln!(
                w,
                r"self.raw.view_bits_mut::<Msb0>()[{start}..{end}].store_be(value);",
            )?;
        }
    }

    Ok(())
}

/// Generate the raw getter and setter for a signal.
fn render_raw_accessors(w: &mut impl Write, signal: &Signal, msg: &Message) -> Result<()> {
    let field = signal.field_name();
    let typ = ValType::from_signal_int(signal);

    writeln!(w, "/// Returns the raw value of `{}`.", signal.name)?;
    writeln!(w, "///")?;
    writeln!(w, "/// - Start bit: {}", signal.start_bit)?;
    writeln!(w, "/// - Signal size: {} bits", signal.size)?;
    writeln!(w, "/// - Byte order: {:?}", signal.byte_order)?;
    writeln!(w, "/// - Value type: {:?}", signal.value_type)?;
    writeln!(w, "#[inline(always)]")?;
    writeln!(w, "pub fn {field}_raw_val(&self) -> {typ} {{")?;
    {
        let mut w = PadAdapter::wrap(&mut *w);
        writeln!(w, "{}", read_fn(signal, msg)?)?;
    }
    writeln!(w, "}}")?;
    writeln!(w)?;

    // To avoid accidentally changing the multiplexor value without changing
    // the signals accordingly this fn is kept private for multiplexors.
    let visibility = if signal.multiplexer_indicator == Multiplexor {
        ""
    } else {
        "pub "
    };

    writeln!(w, "/// Sets the raw value of `{}`.", signal.name)?;
    if visibility.is_empty() {
        // Private multiplexor raw setters have no internal caller.
        writeln!(w, "#[allow(dead_code)]")?;
    }
    writeln!(w, "#[inline(always)]")?;
    writeln!(
        w,
        "{visibility}fn set_{field}_raw_val(&mut self, value: {typ}) {{",
    )?;
    {
        let mut w = PadAdapter::wrap(&mut *w);
        pack_bits(&mut w, signal, msg)?;
    }
    writeln!(w, "}}")?;
    writeln!(w)?;

    Ok(())
}

enum DuplicateType {
    Unique,
    FirstDuplicate,
    Duplicate,
}

/// Variant info for enum generation
struct VariantInfo {
    base_name: String,
    value: i64,
    dup_type: DuplicateType,
    value_type: String,
}

/// Generate variant info for enum generation.
/// For duplicates, uses tuple variants like `Reserved(u8)` instead of separate variants.
fn generate_variant_info(variants: &[ValDescription], signal_ty: ValType) -> Vec<VariantInfo> {
    // First pass: count occurrences of each base name
    let mut name_counts: HashMap<String, usize> = HashMap::new();
    for variant in variants {
        let base_name = enum_variant_name(&variant.description);
        name_counts
            .entry(base_name)
            .and_modify(|c| *c = c.saturating_add(1))
            .or_insert(1);
    }

    // Second pass: generate variant info
    let mut variant_infos = Vec::new();
    let mut seen_names: HashMap<String, usize> = HashMap::new();
    for variant in variants {
        let base_name = enum_variant_name(&variant.description);
        let count = name_counts.get(&base_name).copied().unwrap_or(0);
        let seen_count = seen_names.entry(base_name.clone()).or_insert(0);
        *seen_count = (*seen_count).saturating_add(1);

        let dup_type = if count == 1 {
            DuplicateType::Unique
        } else if *seen_count == 1 {
            DuplicateType::FirstDuplicate
        } else {
            DuplicateType::Duplicate
        };

        variant_infos.push(VariantInfo {
            base_name,
            value: variant.id,
            dup_type,
            value_type: signal_ty.to_string(),
        });
    }
    variant_infos
}

impl Config<'_> {
    fn render_embedded_can_frame(&self, w: &mut impl Write, msg: &Message) -> Result<()> {
        self.impl_embedded_can_frame.fmt_cfg(w, |w| {
            writeln!(
                w,
                "\
impl embedded_can::Frame for {0} {{
    fn new(id: impl Into<Id>, data: &[u8]) -> Option<Self> {{
        if id.into() != Self::MESSAGE_ID {{
            None
        }} else {{
            data.try_into().ok()
        }}
    }}

    fn new_remote(_id: impl Into<Id>, _dlc: usize) -> Option<Self> {{
        unimplemented!()
    }}

    fn is_extended(&self) -> bool {{
        match self.id() {{
            Id::Standard(_) => false,
            Id::Extended(_) => true,
        }}
    }}

    fn is_remote_frame(&self) -> bool {{
        false
    }}

    fn id(&self) -> Id {{
        Self::MESSAGE_ID
    }}

    fn dlc(&self) -> usize {{
        self.raw.len()
    }}

    fn data(&self) -> &[u8] {{
        &self.raw
    }}
}}",
                msg.type_name(),
            )
        })
    }
}

fn render_debug_impl(w: &mut impl Write, msg: &Message) -> Result<()> {
    let typ = msg.type_name();
    writeln!(w, r"impl core::fmt::Debug for {typ} {{")?;
    {
        let mut w = PadAdapter::wrap(w);
        writeln!(
            w,
            "fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {{",
        )?;
        {
            let mut w = PadAdapter::wrap(&mut w);
            writeln!(w, r"if f.alternate() {{")?;
            {
                let mut w = PadAdapter::wrap(&mut w);
                writeln!(w, r#"f.debug_struct("{typ}")"#)?;
                {
                    let mut w = PadAdapter::wrap(&mut w);
                    for signal in &msg.signals {
                        if signal.multiplexer_indicator == Plain {
                            writeln!(w, r#".field("{0}", &self.{0}())"#, signal.field_name())?;
                        }
                    }
                }
                writeln!(w, r".finish()")?;
            }
            writeln!(w, r"}} else {{")?;
            {
                let mut w = PadAdapter::wrap(&mut w);
                writeln!(w, r#"f.debug_tuple("{typ}").field(&self.raw).finish()"#)?;
            }
            writeln!(w, "}}")?;
        }
        writeln!(w, "}}")?;
    }
    writeln!(w, "}}")?;
    writeln!(w)?;
    Ok(())
}

fn render_defmt_impl(w: &mut impl Write, msg: &Message) -> Result<()> {
    let typ = msg.type_name();
    writeln!(w, r"impl defmt::Format for {typ} {{")?;
    {
        let mut w = PadAdapter::wrap(w);
        writeln!(w, "fn format(&self, f: defmt::Formatter) {{")?;
        {
            let mut w = PadAdapter::wrap(&mut w);
            writeln!(w, r"defmt::write!(f,")?;
            {
                let mut w = PadAdapter::wrap(&mut w);
                write!(w, r#""{typ} {{{{"#)?;
                {
                    for signal in &msg.signals {
                        if signal.multiplexer_indicator == Plain {
                            write!(w, r" {}={{:?}}", signal.name)?;
                        }
                    }
                }
                writeln!(w, r#" }}}}","#)?;

                for signal in &msg.signals {
                    if signal.multiplexer_indicator == Plain {
                        writeln!(w, "self.{}(),", signal.field_name())?;
                    }
                }
                writeln!(w, r");")?;
            }
            writeln!(w, "}}")?;
        }
    }
    writeln!(w, "}}")?;
    writeln!(w)?;
    Ok(())
}

impl Config<'_> {
    fn render_multiplexor_enums(
        &self,
        w: &mut impl Write,
        dbc: &Dbc,
        msg: &Message,
        multiplexor_signal: &Signal,
    ) -> Result<()> {
        ensure!(
            multiplexor_signal.multiplexer_indicator == Multiplexor,
            "signal {} is not the multiplexor",
            multiplexor_signal.name,
        );

        let mut multiplexed_signals = BTreeMap::new();
        for signal in &msg.signals {
            if let MultiplexedSignal(switch_index) = signal.multiplexer_indicator {
                multiplexed_signals
                    .entry(switch_index)
                    .and_modify(|v: &mut Vec<&Signal>| v.push(signal))
                    .or_insert_with(|| vec![&signal]);
            }
        }

        writeln!(w, "/// Defined values for multiplexed signal {}", msg.name)?;
        writeln!(w, "{ALLOW_LINTS}")?;
        self.write_allow_dead_code(w)?;

        self.impl_debug.fmt_attr(w, "derive(Debug)")?;
        self.impl_defmt.fmt_attr(w, "derive(defmt::Format)")?;
        self.impl_serde.fmt_attr(w, "derive(Serialize)")?;
        self.impl_serde.fmt_attr(w, "derive(Deserialize)")?;

        let enum_name = multiplex_enum_name(msg, multiplexor_signal)?;
        writeln!(w, "pub enum {enum_name} {{")?;

        {
            let mut w = PadAdapter::wrap(w);
            for switch_index in multiplexed_signals.keys() {
                writeln!(
                    w,
                    "{multiplexed_wrapper_name}({multiplexed_name}),",
                    multiplexed_wrapper_name = multiplexed_enum_variant_wrapper_name(*switch_index),
                    multiplexed_name =
                        multiplexed_enum_variant_name(msg, multiplexor_signal, *switch_index)?,
                )?;
            }
        }
        writeln!(w, "}}")?;
        writeln!(w)?;

        for (switch_index, multiplexed_signals) in &multiplexed_signals {
            let struct_name =
                multiplexed_enum_variant_name(msg, multiplexor_signal, *switch_index)?;

            writeln!(w, "{ALLOW_LINTS}")?;
            self.write_allow_dead_code(w)?;
            self.impl_debug.fmt_attr(w, "derive(Debug)")?;
            self.impl_defmt.fmt_attr(w, "derive(defmt::Format)")?;
            self.impl_serde.fmt_attr(w, "derive(Serialize)")?;
            self.impl_serde.fmt_attr(w, "derive(Deserialize)")?;
            writeln!(w, r"#[derive(Default)]")?;
            writeln!(w, "pub struct {struct_name} {{ raw: [u8; {}] }}", msg.size)?;
            writeln!(w)?;

            writeln!(w, "{ALLOW_LINTS}")?;
            self.write_allow_dead_code(w)?;
            writeln!(w, "impl {struct_name} {{")?;

            writeln!(
                w,
                "pub fn new() -> Self {{ Self {{ raw: [0u8; {}] }} }}",
                msg.size
            )?;

            for signal in multiplexed_signals {
                self.render_signal(w, signal, dbc, msg)?;
            }

            writeln!(w, "}}")?;
            writeln!(w)?;
        }

        Ok(())
    }

    fn render_arbitrary(&self, w: &mut impl Write, dbc: &Dbc, msg: &Message) -> Result<()> {
        writeln!(w, "{ALLOW_LINTS}")?;
        self.write_allow_dead_code(w)?;
        let typ = msg.type_name();
        writeln!(w, "impl<'a> Arbitrary<'a> for {typ} {{")?;
        {
            let filtered_signals: Vec<&Signal> = msg
                .signals
                .iter()
                .filter(|v| matches!(v.multiplexer_indicator, Plain | Multiplexor))
                .collect();
            let mut w = PadAdapter::wrap(w);
            writeln!(
                w,
                "fn arbitrary({}u: &mut Unstructured<'a>) -> Result<Self, arbitrary::Error> {{",
                if filtered_signals.is_empty() { "_" } else { "" },
            )?;
            {
                let mut w = PadAdapter::wrap(&mut w);

                for signal in &filtered_signals {
                    writeln!(
                        w,
                        "let {field_name} = {arbitrary_value};",
                        field_name = signal.field_name(),
                        arbitrary_value = signal_to_arbitrary(signal),
                    )?;
                }

                let args: Vec<String> = filtered_signals
                    .iter()
                    .map(|signal| {
                        let field = signal.field_name();
                        let is_enum_backed = signal_pub_type(dbc, msg, signal)
                            != ValType::from_signal(signal).to_string();
                        if is_enum_backed {
                            format!("{}::_Other({field})", enum_name(msg, signal))
                        } else {
                            field
                        }
                    })
                    .collect();

                writeln!(
                    w,
                    "{typ}::new({args}).map_err(|_| arbitrary::Error::IncorrectFormat)",
                    typ = msg.type_name(),
                    args = args.join(","),
                )?;
            }
            writeln!(w, "}}")?;
        }
        writeln!(w, "}}")?;

        Ok(())
    }

    fn render_error(&self, w: &mut impl Write) -> Result<()> {
        w.write_all(
            r#"
        #[allow(dead_code)]
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum CanError {
    UnknownMessageId(embedded_can::Id),
    /// Signal parameter is not within the range
    /// defined in the dbc
    ParameterOutOfRange {
        /// dbc message id
        message_id: embedded_can::Id,
    },
    InvalidPayloadSize,
    /// Multiplexor value not defined in the dbc
    InvalidMultiplexor {
        /// dbc message id
        message_id: embedded_can::Id,
        /// Multiplexor value not defined in the dbc
        multiplexor: u16,
    },
}

impl core::fmt::Display for CanError {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        write!(f, "{self:?}")
    }
}
        "#
            .as_bytes(),
        )?;

        self.impl_error.fmt_cfg(w, |w| {
            writeln!(w, "impl core::error::Error for CanError {{}}")
        })
    }

    fn render_arbitrary_helpers(&self, w: &mut impl Write) -> Result<()> {
        self.impl_arbitrary.fmt_cfg(&mut *w, |w| {
            self.write_allow_dead_code(w)?;
            writeln!(w, "trait UnstructuredFloatExt {{")?;
            writeln!(w, "    fn float_in_range(&mut self, range: core::ops::RangeInclusive<f32>) -> arbitrary::Result<f32>;")?;
            writeln!(w, "}}")?;
            writeln!(w)?;
            Ok::<_, Error>(())
        })?;

        self.impl_arbitrary.fmt_cfg(w, |w| {
            writeln!(w, "impl UnstructuredFloatExt for arbitrary::Unstructured<'_> {{")?;
            writeln!(w, "    fn float_in_range(&mut self, range: core::ops::RangeInclusive<f32>) -> arbitrary::Result<f32> {{")?;
            writeln!(w, "        let min = range.start();")?;
            writeln!(w, "        let max = range.end();")?;
            writeln!(w, "        let steps = u32::MAX;")?;
            writeln!(w, "        let factor = (max - min) / (steps as f32);")?;
            writeln!(w, "        let random_int: u32 = self.int_in_range(0..=steps)?;")?;
            writeln!(w, "        let random = min + factor * (random_int as f32);")?;
            writeln!(w, "        Ok(random)")?;
            writeln!(w, "    }}")?;
            writeln!(w, "}}")?;
            writeln!(w)?;
            Ok::<_, Error>(())
        })
    }
}

fn signal_to_arbitrary(signal: &Signal) -> String {
    let typ = ValType::from_signal(signal);
    match typ {
        ValType::Bool => "u.int_in_range(0..=1)? == 1".to_string(),
        ValType::F32 => {
            let min = signal.min;
            let max = signal.max;
            format!("u.float_in_range({min}_f32..={max}_f32)?")
        }
        _ => {
            let min = signal.min;
            let max = signal.max;
            format!("u.int_in_range({min}..={max})?")
        }
    }
}

fn get_relevant_messages(dbc: &Dbc) -> impl Iterator<Item = &Message> {
    dbc.messages.iter().filter(|v| !message_ignored(v))
}

fn message_ignored(message: &Message) -> bool {
    // DBC internal message containing signals unassigned to any real message
    message.name == "VECTOR__INDEPENDENT_SIG_MSG"
}

/// Resolve a [`FieldSource`] to a Rust literal.
fn resolve_field_source(source: &FieldSource<'_>, target: &AttrTarget<'_>) -> Option<String> {
    let AttrTarget {
        msg,
        dbc,
        signal,
        node,
    } = *target;
    match source {
        FieldSource::Attr(name) => match (signal, node) {
            (Some(s), None) => dbc.resolved_signal_attribute(msg.id, &s.name, name),
            (None, None) => dbc.resolved_message_attribute(msg.id, name),
            (Some(s), Some(n)) => {
                resolved_node_relation_attribute(dbc, n, msg.id, Some(&s.name), name)
            }
            (None, Some(n)) => resolved_node_relation_attribute(dbc, n, msg.id, None, name),
        }
        .map(attr_value_literal),
        FieldSource::MessageAttr(name) => dbc
            .resolved_message_attribute(msg.id, name)
            .map(attr_value_literal),
        FieldSource::StartBit => signal.map(|s| s.start_bit.to_string()),
        FieldSource::StartByte => signal.map(|s| signal_start_byte(s).to_string()),
        FieldSource::BitWidth => signal.map(|s| s.size.to_string()),
        FieldSource::MessageSize => Some(msg.size.to_string()),
        FieldSource::Int(v) => Some(v.to_string()),
        FieldSource::Str(v) => Some(format!("{v:?}")),
        FieldSource::NodeName => node.map(|n| format!("{n:?}")),
    }
}

/// Lookup an assigned node relation attribute value. This can be either
/// node-to-signal (`BA_REL_ ... BU_SG_REL_`, `signal_name: Some`) or
/// node-to-message (`BA_REL_ ... BU_BO_REL_`, `signal_name: None`).
fn node_relation_attribute<'a>(
    dbc: &'a Dbc,
    node_name: &str,
    message_id: MessageId,
    signal_name: Option<&str>,
    name: &str,
) -> Option<&'a AttributeValue> {
    dbc.relation_attribute_values.iter().find_map(|rel| {
        if rel.name != name {
            return None;
        }
        match (&rel.details, signal_name) {
            (
                AttributeValueForRelationType::NodeToSignal {
                    node_name: n,
                    message_id: mid,
                    signal_name: sig,
                    value,
                },
                Some(want_sig),
            ) if n == node_name && *mid == message_id && sig == want_sig => Some(value),
            (
                AttributeValueForRelationType::NodeToMessage {
                    node_name: n,
                    message_id: mid,
                    value,
                },
                None,
            ) if n == node_name && *mid == message_id => Some(value),
            _ => None,
        }
    })
}

/// Lookup a node relation attribute value.
/// Uses the default (`BA_DEF_DEF_REL_`) if a value is not assigned.
fn resolved_node_relation_attribute<'a>(
    dbc: &'a Dbc,
    node_name: &str,
    message_id: MessageId,
    signal_name: Option<&str>,
    name: &str,
) -> Option<&'a AttributeValue> {
    node_relation_attribute(dbc, node_name, message_id, signal_name, name).or_else(|| {
        dbc.relation_attribute_defaults
            .iter()
            .find(|d| d.name == name)
            .map(|d| &d.value)
    })
}

/// Byte index of a signal's start bit.
fn signal_start_byte(signal: &Signal) -> u64 {
    signal.start_bit.checked_div(8).unwrap_or(0)
}

/// Render an attribute value as an un-suffixed Rust literal.
fn attr_value_literal(value: &AttributeValue) -> String {
    match value {
        AttributeValue::Uint(v) => v.to_string(),
        AttributeValue::Int(v) => v.to_string(),
        AttributeValue::Double(v) => format!("{v:?}"),
        AttributeValue::String(v) => format!("{v:?}"),
    }
}

/// Cycle time in milliseconds from an assigned `GenMsgCycleTime` (`BA_`)
/// attribute, if it is present and a non-negative integer that fits within a `u32`.
fn message_cycle_time_ms(dbc: &Dbc, id: MessageId) -> Option<u32> {
    match dbc.message_attribute(id, "GenMsgCycleTime")? {
        AttributeValue::Uint(v) => u32::try_from(*v).ok(),
        AttributeValue::Int(v) => u32::try_from(*v).ok(),
        AttributeValue::Double(_) | AttributeValue::String(_) => None,
    }
}

impl Config<'_> {
    /// Generate Rust structs matching DBC input description and return as String
    pub fn generate(self) -> Result<String> {
        let mut out = Vec::new();
        self.codegen(&mut out)
            .context("could not generate Rust code")?;
        // Parse and re-format the generated code to allow for future
        // syn/quote codegen migration. Note that this is inefficient at the moment,
        // but this shouldn't be significantly noticeable.
        let out = std::str::from_utf8(&out).context("Failed to convert output to str")?;
        let file = syn::parse_file(out).context("Failed to parse generated Rust code")?;
        Ok(prettyplease::unparse(&file))
    }

    /// Generate Rust structs matching DBC input description and write to `out`
    pub fn write(self, mut out: impl Write) -> Result<()> {
        out.write_all(self.generate()?.as_bytes())?;
        Ok(())
    }

    /// Generate Rust structs matching DBC input description and write to file at `path`
    pub fn write_to_file<P: AsRef<Path>>(self, path: P) -> Result<()> {
        let file = OpenOptions::new()
            .write(true)
            .truncate(true)
            .create(true)
            .open(path.as_ref())?;

        self.write(file)
    }

    fn write_allow_dead_code(&self, w: &mut impl Write) -> Result<()> {
        if self.allow_dead_code {
            writeln!(w, "{ALLOW_DEADCODE}")?;
        }
        Ok(())
    }
}