use std::io::Result;
use std::path::PathBuf;
use std::collections::HashMap;
use lazy_static::lazy_static;
use regex::{Captures,Regex};
use pandoc::{InputFormat,InputKind,OutputFormat,OutputKind,Pandoc};
use pandoc_ast::Block;

type Blocks<'a> = HashMap<&'a str,&'a str>;

fn build(blocks: &Blocks, entry: &str) -> String {
    lazy_static! {
        static ref RE: Regex = Regex::new(r"<<([^>\s]+)>>").unwrap();
    }
    if let Some(entry) = blocks.get(entry).clone() {
        RE.replace_all(entry, |caps: &Captures| blocks.get(&caps[1]).expect("Block not present")).to_string()
    } else {
        String::from("")
    }
}

fn main() -> Result<()> {
    let mut pandoc = Pandoc::new();
    /* Pandoc input setup */
    pandoc.set_input(InputKind::Files(vec![PathBuf::from("test.md")]));
    pandoc.set_input_format(InputFormat::Markdown, vec![]);
    /* Pandoc output setup */
    pandoc.set_output(OutputKind::Pipe);
    pandoc.set_output_format(OutputFormat::Json, vec![]);
    /* Process literate program */
    pandoc.add_filter(|json| pandoc_ast::filter(json, |pandoc| {
        let mut blocks: Blocks = HashMap::new();
        pandoc.blocks.iter().for_each(|block|
            if let Block::CodeBlock(attr, code) = block {
                if attr.0.len() > 0 {
                    blocks.insert(&attr.0, &code);
                } /*else {
                    println!("The following code has no ID:");
                    code.lines().for_each(|l| println!("    {}", l));
                }*/
            }
        );
        let program = build(&blocks, "main.rs");
        println!("{}", program);
        pandoc
    }));
    pandoc.execute().unwrap();
    Ok(())
}