path: root/src/ast.rs

use lazy_static::lazy_static;
use log::trace;
use pandoc_ast::{Map, MetaValue};
use regex::Regex;
use serde::Deserialize;
use serde_yaml::{Mapping, Value};
use std::collections::{BTreeMap, HashMap};
use std::path::{Path, PathBuf};

lazy_static! {
    // Pattern that recognises a YAML block at the beginning of a file.
    static ref LEADING_YAML_PATTERN: Regex = Regex::new(r"^(?:\S*\n)*(?P<yaml>-{3,}\n([^.].*\n)*\.{3,}\n)(?P<text>(.*\n)*)$").unwrap();


    // Pattern that recognises a YAML block at the end of a file.
    static ref TRAILING_YAML_PATTERN: Regex = Regex::new(r"(?P<text>(.*\n)*)\n*(?P<yaml>-{3,}\n([^.].*\n)*\.{3,}\n)(?:\S*\n)*$").unwrap();
}

/// Errors from Markdown parsing.
#[derive(Debug, thiserror::Error)]
pub enum Error {
    #[error(transparent)]
    Regex(#[from] regex::Error),

    #[error("Markdown doesn't contain a YAML block for document metadata")]
    NoMetadata,

    #[error(transparent)]
    Yaml(#[from] serde_yaml::Error),
}

/// Document metadata.
///
/// This is expressed in the Markdown input file as an embedded YAML
/// block.
///
/// Note that this structure needs to be able to capture any metadata
/// block we can work with, in any input file. By being strict here we
/// make it easier to tell the user when a metadata block has, say, a
/// misspelled field.
#[derive(Debug, Default, Clone, Deserialize)]
#[serde(deny_unknown_fields)]
pub struct YamlMetadata {
    title: String,
    subtitle: Option<String>,
    authors: Option<Vec<String>>,
    date: Option<String>,
    classes: Option<Vec<String>>,
    bibliography: Option<Vec<PathBuf>>,
    markdowns: Vec<PathBuf>,
    bindings: Option<Vec<PathBuf>>,
    documentclass: Option<String>,
    #[serde(default)]
    impls: BTreeMap<String, Vec<PathBuf>>,
    pandoc: Option<HashMap<String, Value>>,
}

impl YamlMetadata {
    #[cfg(test)]
    fn new(yaml_text: &str) -> Result<Self, Error> {
        trace!("Parsing YAML");
        let meta: Self = serde_yaml::from_str(yaml_text)?;
        Ok(meta)
    }

    /// Name of file with the Markdown for the subplot document.
    pub fn markdown(&self) -> &Path {
        &self.markdowns[0]
    }

    /// Convert into a pandoc_ast::Map.
    pub fn to_map(&self) -> Map<String, MetaValue> {
        trace!("Creating metadata map from parsed YAML");
        let mut map: Map<String, MetaValue> = Map::new();

        map.insert("title".into(), meta_string(&self.title));

        if let Some(v) = &self.subtitle {
            map.insert("subtitle".into(), meta_string(v));
        }

        if let Some(authors) = &self.authors {
            let authors: Vec<MetaValue> = authors
                .iter()
                .map(|s| MetaValue::MetaString(s.into()))
                .collect();
            map.insert("author".into(), MetaValue::MetaList(authors));
        }

        if let Some(v) = &self.date {
            map.insert("date".into(), meta_string(v));
        }

        if let Some(v) = &self.classes {
            map.insert("classes".into(), meta_strings(v));
        }

        if !self.impls.is_empty() {
            let impls = self
                .impls
                .iter()
                .map(|(k, v)| (k.to_owned(), Box::new(meta_path_bufs(v))))
                .collect();
            map.insert("impls".into(), MetaValue::MetaMap(impls));
        }

        if let Some(v) = &self.bibliography {
            map.insert("bibliography".into(), meta_path_bufs(v));
        }

        if let Some(v) = &self.bindings {
            map.insert("bindings".into(), meta_path_bufs(v));
        }

        if let Some(v) = &self.documentclass {
            map.insert("documentclass".into(), meta_string(v));
        }

        if let Some(pandoc) = &self.pandoc {
            for (key, value) in pandoc.iter() {
                map.insert(key.to_string(), value_to_pandoc(value));
            }
        }

        trace!("Created metadata map from parsed YAML");
        map
    }
}

fn mapping_to_pandoc(mapping: &Mapping) -> MetaValue {
    let mut map = Map::new();
    for (key, value) in mapping.iter() {
        let key = if let MetaValue::MetaString(s) = value_to_pandoc(key) {
            s
        } else {
            panic!("key not a string: {:?}", key);
        };
        map.insert(key, Box::new(value_to_pandoc(value)));
    }

    MetaValue::MetaMap(map)
}

fn value_to_pandoc(data: &Value) -> MetaValue {
    match data {
        Value::Null => unreachable!("null not OK"),
        Value::Number(_) => unreachable!("number not OK"),
        Value::Sequence(_) => unreachable!("sequence not OK"),

        Value::Bool(b) => MetaValue::MetaBool(*b),
        Value::String(s) => MetaValue::MetaString(s.clone()),
        Value::Mapping(mapping) => mapping_to_pandoc(mapping),
    }
}

fn meta_string(s: &str) -> MetaValue {
    MetaValue::MetaString(s.to_string())
}

fn meta_strings(v: &[String]) -> MetaValue {
    MetaValue::MetaList(v.iter().map(|s| meta_string(s)).collect())
}

fn meta_path_buf(p: &Path) -> MetaValue {
    meta_string(&p.display().to_string())
}

fn meta_path_bufs(v: &[PathBuf]) -> MetaValue {
    MetaValue::MetaList(v.iter().map(|p| meta_path_buf(p)).collect())
}

#[cfg(test)]
mod test {
    use super::YamlMetadata;
    use std::path::{Path, PathBuf};

    #[test]
    fn full_meta() {
        let meta = YamlMetadata::new(
            "\
title: Foo Bar
date: today
classes: [json, text]
impls:
  python:
   - foo.py
   - bar.py
bibliography:
- foo.bib
- bar.bib
markdowns:
- test.md
bindings:
- foo.yaml
- bar.yaml
",
        )
        .unwrap();
        assert_eq!(meta.title, "Foo Bar");
        assert_eq!(meta.date.unwrap(), "today");
        assert_eq!(meta.classes.unwrap(), &["json", "text"]);
        assert_eq!(
            meta.bibliography.unwrap(),
            &[path("foo.bib"), path("bar.bib")]
        );
        assert_eq!(meta.markdowns, vec![Path::new("test.md")]);
        assert_eq!(
            meta.bindings.unwrap(),
            &[path("foo.yaml"), path("bar.yaml")]
        );
        assert!(!meta.impls.is_empty());
        for (k, v) in meta.impls.iter() {
            assert_eq!(k, "python");
            assert_eq!(v, &[path("foo.py"), path("bar.py")]);
        }
    }

    fn path(s: &str) -> PathBuf {
        PathBuf::from(s)
    }
}