use anyhow::Result;
use clap::{Arg, ArgMatches, Command};
use mdbook::BookItem;
use mdbook::book::{Book, Chapter};
use mdbook::preprocess::CmdPreprocessor;
use regex::Regex;
use settings::KeymapFile;
use std::io::{self, Read};
use std::process;
use std::sync::LazyLock;

static KEYMAP_MACOS: LazyLock<KeymapFile> = LazyLock::new(|| {
    load_keymap("keymaps/default-macos.json").expect("Failed to load MacOS keymap")
});

static KEYMAP_LINUX: LazyLock<KeymapFile> = LazyLock::new(|| {
    load_keymap("keymaps/default-linux.json").expect("Failed to load Linux keymap")
});

pub fn make_app() -> Command {
    Command::new("zed-docs-preprocessor")
        .about("Preprocesses Zed Docs content to provide rich action & keybinding support and more")
        .subcommand(
            Command::new("supports")
                .arg(Arg::new("renderer").required(true))
                .about("Check whether a renderer is supported by this preprocessor"),
        )
}

fn main() -> Result<()> {
    let matches = make_app().get_matches();

    if let Some(sub_args) = matches.subcommand_matches("supports") {
        handle_supports(sub_args);
    } else {
        handle_preprocessing()?;
    }

    Ok(())
}

fn handle_preprocessing() -> Result<()> {
    let mut stdin = io::stdin();
    let mut input = String::new();
    stdin.read_to_string(&mut input)?;

    let (_ctx, mut book) = CmdPreprocessor::parse_input(input.as_bytes())?;

    template_keybinding(&mut book);
    template_action(&mut book);

    serde_json::to_writer(io::stdout(), &book)?;

    Ok(())
}

fn handle_supports(sub_args: &ArgMatches) -> ! {
    let renderer = sub_args
        .get_one::<String>("renderer")
        .expect("Required argument");
    let supported = renderer != "not-supported";
    if supported {
        process::exit(0);
    } else {
        process::exit(1);
    }
}

fn template_keybinding(book: &mut Book) {
    let regex = Regex::new(r"\{#kb (.*?)\}").unwrap();

    for_each_chapter_mut(book, |chapter| {
        chapter.content = regex
            .replace_all(&chapter.content, |caps: &regex::Captures| {
                let action = caps[1].trim();
                let macos_binding = find_binding("macos", action).unwrap_or_default();
                let linux_binding = find_binding("linux", action).unwrap_or_default();

                if macos_binding.is_empty() && linux_binding.is_empty() {
                    return "<div>No default binding</div>".to_string();
                }

                format!("<kbd class=\"keybinding\">{macos_binding}|{linux_binding}</kbd>")
            })
            .into_owned()
    });
}

fn template_action(book: &mut Book) {
    let regex = Regex::new(r"\{#action (.*?)\}").unwrap();

    for_each_chapter_mut(book, |chapter| {
        chapter.content = regex
            .replace_all(&chapter.content, |caps: &regex::Captures| {
                let name = caps[1].trim();

                let formatted_name = name
                    .chars()
                    .enumerate()
                    .map(|(i, c)| {
                        if i > 0 && c.is_uppercase() {
                            format!(" {}", c.to_lowercase())
                        } else {
                            c.to_string()
                        }
                    })
                    .collect::<String>()
                    .trim()
                    .to_string()
                    .replace("::", ":");

                format!("<code class=\"hljs\">{}</code>", formatted_name)
            })
            .into_owned()
    });
}

fn find_binding(os: &str, action: &str) -> Option<String> {
    let keymap = match os {
        "macos" => &KEYMAP_MACOS,
        "linux" => &KEYMAP_LINUX,
        _ => unreachable!("Not a valid OS: {}", os),
    };

    // Find the binding in reverse order, as the last binding takes precedence.
    keymap.sections().rev().find_map(|section| {
        section.bindings().rev().find_map(|(keystroke, a)| {
            if name_for_action(a.to_string()) == action {
                Some(keystroke.to_string())
            } else {
                None
            }
        })
    })
}

/// Removes any configurable options from the stringified action if existing,
/// ensuring that only the actual action name is returned. If the action consists
/// only of a string and nothing else, the string is returned as-is.
///
/// Example:
///
/// This will return the action name unmodified.
///
/// ```
/// let action_as_str = "assistant::Assist";
/// let action_name = name_for_action(action_as_str);
/// assert_eq!(action_name, "assistant::Assist");
/// ```
///
/// This will return the action name with any trailing options removed.
///
///
/// ```
/// let action_as_str = "\"editor::ToggleComments\", {\"advance_downwards\":false}";
/// let action_name = name_for_action(action_as_str);
/// assert_eq!(action_name, "editor::ToggleComments");
/// ```
fn name_for_action(action_as_str: String) -> String {
    action_as_str
        .split(",")
        .next()
        .map(|name| name.trim_matches('"').to_string())
        .unwrap_or(action_as_str)
}

fn load_keymap(asset_path: &str) -> Result<KeymapFile> {
    let content = util::asset_str::<settings::SettingsAssets>(asset_path);
    KeymapFile::parse(content.as_ref())
}

fn for_each_chapter_mut<F>(book: &mut Book, mut func: F)
where
    F: FnMut(&mut Chapter),
{
    book.for_each_mut(|item| {
        let BookItem::Chapter(chapter) = item else {
            return;
        };
        func(chapter);
    });
}