simploxide-bindgen 0.4.0

//! Turns COMMANDS.md file into na Iterator of [`crate::commands::CommandResponse`].

use convert_case::{Case, Casing as _};

use crate::{
    parse_utils,
    types::{
        DiscriminatedUnionType, Field, RecordType, TopLevelDocs,
        discriminated_union_type::DiscriminatedUnionVariant,
    },
};

pub fn parse(commands_md: &str) -> impl Iterator<Item = Result<CommandResponse, String>> {
    let mut parser = Parser::default();

    commands_md
        .split("---")
        .skip(1)
        .filter_map(|s| {
            let trimmed = s.trim();
            (!trimmed.is_empty()).then_some(trimmed)
        })
        .map(move |blk| parser.parse_block(blk))
}

pub struct CommandResponse {
    pub command: RecordType,
    pub response: DiscriminatedUnionType,
}

/// Generates the provided trait method for the ClientApi trait.
///
/// The ClientApi trait definition itself must be generated by the client and should look like this
///
/// ```ignore
/// pub trait ClientApi {
///     type Error;
///
///     fn send_raw(&self, command: String) -> impl Future<Output = Result<Arc<{}>, Self::Error>> + Send;
///
///     //..
/// }
/// ```
///
/// Then the provided methods could be inserted.
///
/// For methods that return multiple kinds a valid responses the additional wrapper type should be
/// generated. You can get this type definition using the
/// [`CommandResponseTraitMethod::response_wrapper`] method.
pub struct CommandResponseTraitMethod<'a> {
    pub command: &'a RecordType,
    pub response: &'a DiscriminatedUnionType,
    pub shapes: &'a [RecordType],
}

impl<'a> CommandResponseTraitMethod<'a> {
    pub fn new(
        command: &'a RecordType,
        response: &'a DiscriminatedUnionType,
        shapes: &'a [RecordType],
    ) -> Self {
        Self {
            command,
            response,
            shapes,
        }
    }
}

impl<'a> CommandResponseTraitMethod<'a> {
    /// If some method has multiple valid responses a helper type representing valid response
    /// variants must be generated.
    ///
    /// If only one possible valid response is possible it can get inlined without extra helper
    /// types and for this case this method returns `None`.
    pub fn response_wrapper(&self) -> Option<ResponseWrapperFmt> {
        if self.can_inline_response().is_some() {
            return None;
        }

        Some(ResponseWrapperFmt(DiscriminatedUnionType::new(
            self.response_wrapper_name(),
            self.valid_responses()
                .cloned()
                .zip(self.valid_response_shapes())
                .map(|(mut resp, shape)| {
                    if shape.fields.len() == 1 {
                        resp.fields[0] = Field {
                            api_name: String::new(),
                            rust_name: String::new(),
                            typ: shape.fields[0].typ.clone(),
                        }
                    }

                    resp
                })
                .collect(),
        )))
    }

    /// Instead of accepting a command type directly we can accept its arguments and construct it
    /// internally.
    ///
    /// ```ignore
    ///     fn api_show_my_address(cmd: ApiShowMyAddressCommand) -> ...
    /// ```
    ///
    /// turns into
    ///
    /// ```ignore
    ///     fn api_show_my_address(user_id: i64) -> ... {
    ///         let cmd = ApiShowMyAddressCommand { user_id };
    ///     }
    /// ```
    ///
    /// This condition determines when such transformation takes place
    fn can_inline_args(&self) -> bool {
        !self
            .command
            .fields
            .iter()
            .any(|f| f.is_optional() || f.is_bool())
    }

    /// If response consists only of a single valid variant this variant's inner struct can be
    /// used directly as a return value of the API method.
    fn can_inline_response(&self) -> Option<&DiscriminatedUnionVariant> {
        if self.valid_responses().count() == 1 {
            self.valid_responses().next()
        } else {
            None
        }
    }

    /// If underlying struct of the response contains only a single documented field this field can be directly
    /// returned instead of returning the whole response struct.
    fn can_inline_response_shape(&self) -> Option<&Field> {
        if self.valid_response_shapes().count() != 1 {
            return None;
        }

        let shape = self.valid_response_shapes().next().unwrap();

        if shape.fields.len() == 1 {
            Some(&shape.fields[0])
        } else {
            None
        }
    }

    fn valid_responses(&self) -> impl Iterator<Item = &'_ DiscriminatedUnionVariant> {
        self.response
            .variants
            .iter()
            .filter(|x| x.rust_name != "ChatCmdError")
    }

    fn valid_response_shapes(&self) -> impl Iterator<Item = &'_ RecordType> {
        self.shapes.iter().filter(|x| x.name != "ChatCmdError")
    }

    fn response_wrapper_name(&self) -> String {
        format!("{}s", self.response.name)
    }
}

impl<'a> std::fmt::Display for CommandResponseTraitMethod<'a> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        self.command.write_docs_fmt(f)?;
        write!(
            f,
            "    fn {}(&self",
            self.command.name.remove_empty().to_case(Case::Snake)
        )?;

        let (ret_type, unwrapped_response_typename) =
            if let Some(inlined_variant) = self.can_inline_response() {
                let typename = if let Some(field) = self.can_inline_response_shape() {
                    field.typ.clone()
                } else {
                    inlined_variant.fields[0].typ.clone()
                };

                (format!("Arc<{typename}>"), typename)
            } else {
                let typename = self.response_wrapper_name();
                (typename.clone(), typename)
            };

        if self.can_inline_args() {
            for field in self.command.fields.iter() {
                write!(f, ", {}: {}", field.rust_name, field.typ)?;
            }

            writeln!(
                f,
                ") -> impl Future<Output = Result<{ret_type}, Self::Error>> + Send {{ async move {{",
            )?;
            write!(f, "        let command = {} {{", self.command.name)?;

            for (ix, field) in self.command.fields.iter().enumerate() {
                if ix > 0 {
                    write!(f, ", ")?;
                }

                write!(f, "{}", field.rust_name)?;
            }
            writeln!(f, "}};")?;
        } else {
            writeln!(
                f,
                ", command: {}) -> impl Future<Output = Result<{ret_type}, Self::Error>> + Send {{ async move {{",
                self.command.name,
            )?;
        }

        writeln!(
            f,
            "        let json = self.send_raw(command.to_command_string()).await?;"
        )?;
        writeln!(
            f,
            "        // Safe to unwrap because unrecognized JSON goes to undocumented variant"
        )?;
        writeln!(
            f,
            "        let response = serde_json::from_value(json).unwrap();"
        )?;
        writeln!(f, "        match response {{")?;

        if let Some(variant) = self.can_inline_response() {
            if let Some(field) = self.can_inline_response_shape() {
                writeln!(
                    f,
                    "            {}::{}(resp) => Ok(Arc::new(resp.{})),",
                    self.response.name, variant.rust_name, field.rust_name,
                )?;
            } else {
                writeln!(
                    f,
                    "            {}::{}(resp) => Ok(Arc::new(resp)),",
                    self.response.name, variant.rust_name
                )?;
            }
        } else {
            for (variant, shape) in self.valid_responses().zip(self.valid_response_shapes()) {
                if shape.fields.len() == 1 {
                    writeln!(
                        f,
                        "            {resp_name}::{var_name}(resp) => Ok({typename}::{var_name}(Arc::new(resp.{field}))),",
                        resp_name = self.response.name,
                        typename = unwrapped_response_typename,
                        var_name = variant.rust_name,
                        field = shape.fields[0].rust_name,
                    )?;
                } else {
                    writeln!(
                        f,
                        "            {}::{var_name}(resp) => Ok({}::{var_name}(Arc::new(resp))),",
                        self.response.name,
                        unwrapped_response_typename,
                        var_name = variant.rust_name,
                    )?;
                }
            }
        }

        writeln!(
            f,
            "            {}::ChatCmdError(resp) => Err(BadResponseError::ChatCmdError(Arc::new(resp.chat_error)).into()),",
            self.response.name,
        )?;
        writeln!(
            f,
            "            {}::Undocumented(resp) => Err(BadResponseError::Undocumented(resp).into()),",
            self.response.name,
        )?;
        writeln!(f, "        }}")?;

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

/// Use this formatter for command types instead of the standard std::fmt::Display impl of the
/// [`RecordType`]. This impl strips down all serialization attributes and undocumented fields.
pub struct CommandFmt<'a>(pub &'a RecordType);

impl std::fmt::Display for CommandFmt<'_> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        self.0.write_docs_fmt(f)?;

        writeln!(f, "#[derive(Debug, Clone, PartialEq)]")?;
        writeln!(f, "#[cfg_attr(feature = \"bon\", derive(::bon::Builder))]")?;

        writeln!(f, "pub struct {} {{", self.0.name)?;

        for field in self.0.fields.iter() {
            writeln!(f, "    pub {}: {},", field.rust_name, field.typ)?;
        }

        writeln!(f, "}}")
    }
}

pub struct ResponseWrapperFmt(pub DiscriminatedUnionType);

impl std::fmt::Display for ResponseWrapperFmt {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        writeln!(
            f,
            "#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]"
        )?;
        writeln!(f, "#[serde(tag = \"type\")]")?;
        writeln!(f, "pub enum {} {{", self.0.name)?;

        for variant in &self.0.variants {
            for comment_line in &variant.doc_comments {
                writeln!(f, "    /// {}", comment_line)?;
            }
            writeln!(f, "    #[serde(rename = \"{}\")]", variant.api_name)?;
            writeln!(
                f,
                "    {}(Arc<{}>),",
                variant.rust_name, variant.fields[0].typ
            )?;
        }
        writeln!(f, "}}\n")?;

        // Gen helper getters
        writeln!(f, "impl {} {{", self.0.name)?;

        for var in self.0.variants.iter() {
            assert_eq!(var.fields.len(), 1, "Discriminated union is not disjointed");
            assert!(
                var.fields[0].rust_name.is_empty(),
                "Discriminated union is not disjointed"
            );

            writeln!(
                f,
                "    pub fn {}(&self) -> Option<&{}> {{",
                var.rust_name.remove_empty().to_case(Case::Snake),
                var.fields[0].typ
            )?;

            writeln!(f, "        if let Self::{}(ret) = self {{", var.rust_name)?;
            writeln!(f, "            Some(ret)",)?;
            writeln!(f, "        }} else {{ None }}",)?;
            writeln!(f, "    }}\n")?;
        }

        writeln!(f, "}}")
    }
}

#[derive(Default)]
struct Parser {
    current_doc_section: Option<DocSection>,
}

impl Parser {
    pub fn parse_block(&mut self, block: &str) -> Result<CommandResponse, String> {
        self.parser(block.lines().map(str::trim))
            .map_err(|e| format!("{e} in block\n```\n{block}\n```"))
    }

    fn parser<'a>(
        &mut self,
        mut lines: impl Iterator<Item = &'a str>,
    ) -> Result<CommandResponse, String> {
        const DOC_SECTION_PAT: &str = parse_utils::H2;
        const TYPENAME_PAT: &str = parse_utils::H3;
        const TYPEKINDS_PAT: &str = parse_utils::BOLD;

        let mut next =
            parse_utils::skip_empty(&mut lines).ok_or_else(|| "Got an empty block".to_owned())?;

        let mut command_docs: Vec<String> = Vec::new();

        let (typename, mut typekind) = loop {
            if let Some(section_name) = next.strip_prefix(DOC_SECTION_PAT) {
                let mut doc_section = DocSection::new(section_name.to_owned());

                next = parse_utils::parse_doc_lines(&mut lines, &mut doc_section.contents, |s| {
                    s.starts_with(TYPENAME_PAT)
                })
                .ok_or_else(|| format!("Failed to find a typename by pattern {TYPENAME_PAT:?} after the doc section"))?;

                self.current_doc_section.replace(doc_section);
            } else if let Some(name) = next.strip_prefix(TYPENAME_PAT) {
                next = parse_utils::parse_doc_lines(&mut lines, &mut command_docs, |s| {
                    s.starts_with(TYPEKINDS_PAT)
                })
                .map(|s| s.strip_prefix(TYPEKINDS_PAT).unwrap())
                .ok_or_else(|| format!("Failed to find a typekind by pattern {TYPEKINDS_PAT:?} after the inner docs "))?;

                break (name, next);
            }
        };

        let command_name = typename.to_case(Case::Pascal);
        let mut command = RecordType::new(command_name.clone(), vec![]);

        loop {
            if typekind.starts_with("Parameters") {
                typekind = parse_utils::parse_record_fields(
                    &mut lines,
                    &mut command.fields,
                    |s| s.starts_with(TYPEKINDS_PAT),
                )?
                .map(|s| s.strip_prefix(TYPEKINDS_PAT).unwrap())
                .ok_or_else(|| format!(
                    "Failed to find a command syntax after parameters by pattern {TYPENAME_PAT:?}"
                ))?;
            } else if typekind.starts_with("Syntax") {
                parse_utils::parse_syntax(&mut lines, &mut command.syntax)?;
                break;
            }
        }

        let mut response_variants: Vec<DiscriminatedUnionVariant> = Vec::with_capacity(4);

        parse_utils::skip_while(&mut lines, |s| !s.starts_with("**Response")).ok_or_else(|| {
            "Failed to find responses section by pattern \"**Response\"".to_owned()
        })?;

        let mut variant_docline = Vec::new();

        while let Some(docline) = parse_utils::skip_empty(&mut lines) {
            if docline.starts_with(TYPEKINDS_PAT) {
                break;
            } else {
                variant_docline.push(docline.to_owned());
            }

            let (mut variant, next) = parse_utils::parse_discriminated_union_variant(&mut lines)?;
            assert!(next.map(|s| s.is_empty()).unwrap_or(true));
            variant.doc_comments = std::mem::take(&mut variant_docline);
            response_variants.push(variant);
        }

        let response =
            DiscriminatedUnionType::new(format!("{command_name}Response"), response_variants);

        if let Some(ref outer_docs) = self.current_doc_section {
            command
                .doc_comments
                .push(format!("### {}", outer_docs.header.clone()));

            command.doc_comments.push(String::new());

            command
                .doc_comments
                .extend(outer_docs.contents.iter().cloned());

            command.doc_comments.push(String::new());
            command.doc_comments.push("----".to_owned());
            command.doc_comments.push(String::new());
        }

        command.doc_comments.extend(command_docs);
        Ok(CommandResponse { command, response })
    }
}

#[derive(Default, Clone)]
struct DocSection {
    header: String,
    contents: Vec<String>,
}

impl DocSection {
    fn new(header: String) -> Self {
        Self {
            header,
            contents: Vec::new(),
        }
    }
}