use std::{env, error::Error};

type DynError = Box<dyn Error>;

pub mod helpers {
    use std::path::{Path, PathBuf};

    use crate::path;
    use helix_core::syntax::Configuration as LangConfig;
    use helix_term::health::TsFeature;

    /// Get the list of languages that support a particular tree-sitter
    /// based feature.
    pub fn ts_lang_support(feat: TsFeature) -> Vec<String> {
        let queries_dir = path::ts_queries();

        find_files(&queries_dir, feat.runtime_filename())
            .iter()
            .map(|f| {
                // .../helix/runtime/queries/python/highlights.scm
                let tail = f.strip_prefix(&queries_dir).unwrap(); // python/highlights.scm
                let lang = tail.components().next().unwrap(); // python
                lang.as_os_str().to_string_lossy().to_string()
            })
            .collect()
    }

    /// Get the list of languages that have any form of tree-sitter
    /// queries defined in the runtime directory.
    pub fn langs_with_ts_queries() -> Vec<String> {
        std::fs::read_dir(path::ts_queries())
            .unwrap()
            .filter_map(|entry| {
                let entry = entry.ok()?;
                entry
                    .file_type()
                    .ok()?
                    .is_dir()
                    .then(|| entry.file_name().to_string_lossy().to_string())
            })
            .collect()
    }

    // naive implementation, but suffices for our needs
    pub fn find_files(dir: &Path, filename: &str) -> Vec<PathBuf> {
        std::fs::read_dir(dir)
            .unwrap()
            .filter_map(|entry| {
                let path = entry.ok()?.path();
                if path.is_dir() {
                    Some(find_files(&path, filename))
                } else {
                    (path.file_name()?.to_string_lossy() == filename).then(|| vec![path])
                }
            })
            .flatten()
            .collect()
    }

    pub fn lang_config() -> LangConfig {
        let bytes = std::fs::read(path::lang_config()).unwrap();
        toml::from_slice(&bytes).unwrap()
    }
}

pub mod md_gen {
    use crate::DynError;

    use crate::helpers;
    use crate::path;
    use helix_term::commands::TYPABLE_COMMAND_LIST;
    use helix_term::health::TsFeature;
    use std::fs;

    pub const TYPABLE_COMMANDS_MD_OUTPUT: &str = "typable-cmd.md";
    pub const LANG_SUPPORT_MD_OUTPUT: &str = "lang-support.md";

    fn md_table_heading(cols: &[String]) -> String {
        let mut header = String::new();
        header += &md_table_row(cols);
        header += &md_table_row(&vec!["---".to_string(); cols.len()]);
        header
    }

    fn md_table_row(cols: &[String]) -> String {
        format!("| {} |\n", cols.join(" | "))
    }

    fn md_mono(s: &str) -> String {
        format!("`{}`", s)
    }

    pub fn typable_commands() -> Result<String, DynError> {
        let mut md = String::new();
        md.push_str(&md_table_heading(&[
            "Name".to_owned(),
            "Description".to_owned(),
        ]));

        let cmdify = |s: &str| format!("`:{}`", s);

        for cmd in TYPABLE_COMMAND_LIST {
            let names = std::iter::once(&cmd.name)
                .chain(cmd.aliases.iter())
                .map(|a| cmdify(a))
                .collect::<Vec<_>>()
                .join(", ");

            md.push_str(&md_table_row(&[names.to_owned(), cmd.doc.to_owned()]));
        }

        Ok(md)
    }

    pub fn lang_features() -> Result<String, DynError> {
        let mut md = String::new();
        let ts_features = TsFeature::all();

        let mut cols = vec!["Language".to_owned()];
        cols.append(
            &mut ts_features
                .iter()
                .map(|t| t.long_title().to_string())
                .collect::<Vec<_>>(),
        );
        cols.push("Default LSP".to_owned());

        md.push_str(&md_table_heading(&cols));
        let config = helpers::lang_config();

        let mut langs = config
            .language
            .iter()
            .map(|l| l.language_id.clone())
            .collect::<Vec<_>>();
        langs.sort_unstable();

        let mut ts_features_to_langs = Vec::new();
        for &feat in ts_features {
            ts_features_to_langs.push((feat, helpers::ts_lang_support(feat)));
        }

        let mut row = Vec::new();
        for lang in langs {
            let lc = config
                .language
                .iter()
                .find(|l| l.language_id == lang)
                .unwrap(); // lang comes from config
            row.push(lc.language_id.clone());

            for (_feat, support_list) in &ts_features_to_langs {
                row.push(
                    if support_list.contains(&lang) {
                        "✓"
                    } else {
                        ""
                    }
                    .to_owned(),
                );
            }
            row.push(
                lc.language_server
                    .as_ref()
                    .map(|s| s.command.clone())
                    .map(|c| md_mono(&c))
                    .unwrap_or_default(),
            );

            md.push_str(&md_table_row(&row));
            row.clear();
        }

        Ok(md)
    }

    pub fn write(filename: &str, data: &str) {
        let error = format!("Could not write to {}", filename);
        let path = path::book_gen().join(filename);
        fs::write(path, data).expect(&error);
    }
}

pub mod path {
    use std::path::{Path, PathBuf};

    pub fn project_root() -> PathBuf {
        Path::new(env!("CARGO_MANIFEST_DIR"))
            .parent()
            .unwrap()
            .to_path_buf()
    }

    pub fn book_gen() -> PathBuf {
        project_root().join("book/src/generated/")
    }

    pub fn ts_queries() -> PathBuf {
        project_root().join("runtime/queries")
    }

    pub fn lang_config() -> PathBuf {
        project_root().join("languages.toml")
    }
}

pub mod tasks {
    use crate::md_gen;
    use crate::DynError;

    pub fn docgen() -> Result<(), DynError> {
        use md_gen::*;
        write(TYPABLE_COMMANDS_MD_OUTPUT, &typable_commands()?);
        write(LANG_SUPPORT_MD_OUTPUT, &lang_features()?);
        Ok(())
    }

    pub fn print_help() {
        println!(
            "
Usage: Run with `cargo xtask <task>`, eg. `cargo xtask docgen`.

    Tasks:
        docgen: Generate files to be included in the mdbook output.
"
        );
    }
}

fn main() -> Result<(), DynError> {
    let task = env::args().nth(1);
    match task {
        None => tasks::print_help(),
        Some(t) => match t.as_str() {
            "docgen" => tasks::docgen()?,
            invalid => return Err(format!("Invalid task name: {}", invalid).into()),
        },
    };
    Ok(())
}