use fluent_syntax::ast::Entry;
use fluent_syntax::parser::Parser;
use std::collections::HashMap;
use std::path::Path;
use std::{fs, path::PathBuf};

fn get_identifiers(ftl_text: &str) -> Vec<String> {
    let res = Parser::new(ftl_text).parse().unwrap();
    let mut idents = vec![];

    for entry in res.body {
        if let Entry::Message(m) = entry {
            idents.push(m.id.name.to_string());
        }
    }

    idents.sort_unstable();

    idents
}

fn proto_enum(idents: &[String]) -> String {
    let mut buf = String::from(
        r#"// This file is automatically generated as part of the build process.

syntax = "proto3";
package FluentProto;
enum FluentString {
"#,
    );
    for (idx, s) in idents.iter().enumerate() {
        let name = s.replace("-", "_").to_uppercase();
        buf += &format!("  {} = {};\n", name, idx);
    }

    buf += "}\n";

    buf
}

fn rust_string_vec(idents: &[String]) -> String {
    let mut buf = String::from(
        r#"// This file is automatically generated as part of the build process.

pub(super) const FLUENT_KEYS: &[&str] = &[
"#,
    );

    for s in idents {
        buf += &format!("    \"{}\",\n", s);
    }

    buf += "];\n";

    buf
}

struct FTLData {
    templates: Vec<String>,
    /// lang -> [FileContent]
    translations: HashMap<String, Vec<String>>,
}

fn get_ftl_data(ftl_list_path: Option<String>) -> FTLData {
    if let Some(path) = ftl_list_path {
        let sources = fs::read_to_string(&path).expect("missing ftl list");
        get_ftl_data_from_provided_files(sources)
    } else {
        get_ftl_data_from_source_tree()
    }
}

/// Extract string of provided files, and read their data.
fn get_ftl_data_from_provided_files(sources: String) -> FTLData {
    let mut templates: Vec<String> = vec![];
    let mut translations: HashMap<String, Vec<String>> = HashMap::new();

    for path in sources.split(' ') {
        let path = path.trim();
        let mut elems = path.rsplit('/');
        let (_fname, first_parent, second_parent) = (
            elems.next().unwrap(),
            elems.next().unwrap(),
            elems.next().unwrap(),
        );
        let entry = std::fs::read_to_string(path).unwrap_or_else(|_| {
            // try parent folder, for cases when we're running from build script
            let path = Path::new("..").join(path);
            std::fs::read_to_string(path).unwrap()
        });
        if !entry.ends_with('\n') {
            panic!(".ftl file should end with a newline: {}", path);
        }
        match (first_parent, second_parent) {
            // templates in the rslib translation repo are ignored, as their canonical
            // form is part of this source tree
            ("templates", "core") => (),
            // templates from this source tree and extra_ftl get merged together
            ("ftl", _) => templates.push(entry),
            ("templates", _) => templates.push(entry),
            // and translations for a given language get merged together
            (lang, _) => translations
                .entry(lang.to_string())
                .or_default()
                .push(entry),
        }
    }

    FTLData {
        templates,
        translations,
    }
}

/// Called when no srcs.list file is available; we include the built-in
/// English templates, and no translations.
fn get_ftl_data_from_source_tree() -> FTLData {
    let mut templates: Vec<String> = vec![];
    for entry in fs::read_dir("ftl").unwrap() {
        let entry = entry.unwrap();
        let fname = entry.file_name().into_string().unwrap();
        if fname.ends_with(".ftl") {
            templates.push(fs::read_to_string(entry.path()).unwrap());
        }
    }

    FTLData {
        templates,
        translations: Default::default(),
    }
}

/// Map of lang->content; Template lang is "template".
fn merge_ftl_data(data: FTLData) -> HashMap<String, String> {
    data.translations
        .into_iter()
        .map(|(lang, content)| (lang, content.join("\n")))
        .chain(std::iter::once((
            "template".to_string(),
            data.templates.join("\n"),
        )))
        .collect()
}

fn write_merged_ftl_files(dir: &Path, data: &HashMap<String, String>) {
    for (lang, content) in data {
        let path = dir.join(format!("{}.ftl", lang));
        fs::write(&path, content).unwrap();
    }
}

fn write_fluent_keys_rs(dir: &Path, idents: &[String]) {
    let path = dir.join("fluent_keys.rs");
    fs::write(&path, rust_string_vec(idents)).unwrap();
}

fn write_fluent_proto_inner(path: &Path, idents: &[String]) {
    fs::write(&path, proto_enum(idents)).unwrap();
}

/// Write fluent.proto into the provided dir.
/// Can be called separately to provide a proto
/// to downstream code.
pub fn write_fluent_proto(out_path: &str, ftl_list: String) {
    let merged_ftl = merge_ftl_data(get_ftl_data(Some(ftl_list)));
    let idents = get_identifiers(merged_ftl.get("template").unwrap());
    write_fluent_proto_inner(Path::new(out_path), &idents);
}

/// Write all ftl-related files into OUT_DIR.
pub fn write_ftl_files_and_fluent_rs() {
    let dir = PathBuf::from(std::env::var("OUT_DIR").unwrap());
    let ftl_list = std::env::var("FTL_FILES").ok();
    let merged_ftl = merge_ftl_data(get_ftl_data(ftl_list));
    write_merged_ftl_files(&dir, &merged_ftl);

    let idents = get_identifiers(merged_ftl.get("template").unwrap());
    write_fluent_keys_rs(&dir, &idents);
    write_fluent_proto_inner(&dir.join("fluent.proto"), &idents);
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn all() {
        let idents = get_identifiers("key-one = foo\nkey-two = bar");
        assert_eq!(idents, vec!["key-one", "key-two"]);

        assert_eq!(
            proto_enum(&idents),
            r#"// This file is automatically generated as part of the build process.

syntax = "proto3";
package backend_strings;
enum FluentString {
  KEY_ONE = 0;
  KEY_TWO = 1;
}
"#
        );

        assert_eq!(
            rust_string_vec(&idents),
            r#"// This file is automatically generated as part of the build process.

const FLUENT_KEYS: &[&str] = &[
    "key-one",
    "key-two",
];
"#
        );
    }
}