nomo/src/lib.rs

use std::collections::HashMap;

use displaydoc::Display;
use thiserror::Error;

use crate::compiler::VMInstructions;
use crate::functions::FunctionMap;
use crate::input::NomoInput;
use crate::value::NomoValue;
use crate::value::NomoValueError;

pub mod compiler;
pub mod eval;
pub mod functions;
pub mod input;
pub mod lexer;
pub mod parser;
pub mod value;

#[derive(Debug, Error, Display)]
pub enum NomoError {
    /// Could not parse the given template
    ParseError {
        #[from]
        source: lexer::ParseFailure,
    },
    /// Invalid Template
    AstError {
        #[from]
        source: parser::AstFailure,
    },

    /// An error occurred while evaluating
    EvaluationError {
        #[from]
        source: eval::EvaluationError,
    },

    /// The template '{0}' could not be found
    UnknownTemplate(String),
}

pub struct Nomo {
    templates: HashMap<String, Template>,
    function_map: FunctionMap,
}

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

impl Nomo {
    pub fn new() -> Nomo {
        Nomo {
            templates: HashMap::new(),
            function_map: FunctionMap::default(),
        }
    }

    pub fn add_template(
        &mut self,
        name: impl Into<String>,
        value: impl Into<NomoInput>,
    ) -> Result<(), NomoError> {
        let source = value.into();
        let parse = lexer::parse(source.clone())?;
        let ast = parser::parse(parse.tokens())?;

        let instructions = compiler::emit_machine(ast);

        self.templates
            .insert(name.into(), Template { instructions });

        Ok(())
    }

    pub fn render(&self, name: &str, ctx: &Context) -> Result<String, NomoError> {
        let template = self
            .templates
            .get(name)
            .ok_or_else(|| NomoError::UnknownTemplate(name.to_string()))?;

        let res = eval::execute(&self.function_map, &template.instructions, ctx)?;

        Ok(res)
    }
}

struct Template {
    instructions: VMInstructions,
}

pub struct Context {
    values: HashMap<String, NomoValue>,
}

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

impl Context {
    pub fn new() -> Context {
        Context {
            values: HashMap::new(),
        }
    }

    pub fn try_insert(
        &mut self,
        key: impl Into<String>,
        value: impl TryInto<NomoValue, Error = NomoValueError>,
    ) -> Result<(), NomoValueError> {
        self.values.insert(key.into(), value.try_into()?);

        Ok(())
    }

    pub fn insert(&mut self, key: impl Into<String>, value: impl Into<NomoValue>) {
        self.values.insert(key.into(), value.into());
    }

    pub fn values(&self) -> &HashMap<String, NomoValue> {
        &self.values
    }
}

#[derive(Debug, Clone)]
pub struct SourceSpan {
    pub range: std::ops::Range<usize>,
}

// This is just like the standard .resume_after(), except we only resume on Cut errors.
fn resume_after_cut<Input, Output, Error, ParseNext, ParseRecover>(
    mut parser: ParseNext,
    mut recover: ParseRecover,
) -> impl winnow::Parser<Input, Option<Output>, Error>
where
    Input: winnow::stream::Stream + winnow::stream::Recover<Error>,
    Error: winnow::error::ParserError<Input> + winnow::error::FromRecoverableError<Input, Error>,
    ParseNext: winnow::Parser<Input, Output, Error>,
    ParseRecover: winnow::Parser<Input, (), Error>,
{
    winnow::combinator::trace("resume_after_cut", move |input: &mut Input| {
        resume_after_cut_inner(&mut parser, &mut recover, input)
    })
}

fn resume_after_cut_inner<P, R, I, O, E>(
    parser: &mut P,
    recover: &mut R,
    i: &mut I,
) -> winnow::Result<Option<O>, E>
where
    P: winnow::Parser<I, O, E>,
    R: winnow::Parser<I, (), E>,
    I: winnow::stream::Stream,
    I: winnow::stream::Recover<E>,
    E: winnow::error::ParserError<I> + winnow::error::FromRecoverableError<I, E>,
{
    let token_start = i.checkpoint();
    let mut err = match parser.parse_next(i) {
        Ok(o) => {
            return Ok(Some(o));
        }
        Err(e) if e.is_incomplete() || e.is_backtrack() => {
            return Err(e);
        }
        Err(err) => err,
    };
    let err_start = i.checkpoint();
    if recover.parse_next(i).is_ok() {
        if let Err(err_) = i.record_err(&token_start, &err_start, err) {
            err = err_;
        } else {
            return Ok(None);
        }
    }

    i.reset(&err_start);
    err = E::from_recoverable_error(&token_start, &err_start, i, err);
    Err(err)
}

#[cfg(test)]
mod tests {
    use crate::Context;
    use crate::Nomo;

    #[test]
    fn check_simple_template() {
        let mut temp = Nomo::new();

        temp.add_template("base", "Hello {{= name }}").unwrap();

        let mut ctx = Context::new();
        ctx.insert("name", "World");

        let rendered = temp.render("base", &ctx).unwrap();

        insta::assert_snapshot!(rendered, @"Hello World")
    }
}