use std::io::{self, Write};
use std::path::{Path, PathBuf};
use std::process::{Command, Stdio};
use std::str::FromStr;

use anyhow::{bail, format_err};
use clap::Parser;
use fs_err as fs;
use fs_err::OpenOptions;

use super::resolve_path;

static MODEL_PROJECT: &str =
    include_str!("../../assets/default-model-project/default.project.json");
static MODEL_README: &str = include_str!("../../assets/default-model-project/README.md");
static MODEL_INIT: &str = include_str!("../../assets/default-model-project/src-init.luau");
static MODEL_GIT_IGNORE: &str = include_str!("../../assets/default-model-project/gitignore.txt");

static PLACE_PROJECT: &str =
    include_str!("../../assets/default-place-project/default.project.json");
static PLACE_README: &str = include_str!("../../assets/default-place-project/README.md");
static PLACE_GIT_IGNORE: &str = include_str!("../../assets/default-place-project/gitignore.txt");

static PLUGIN_PROJECT: &str =
    include_str!("../../assets/default-plugin-project/default.project.json");
static PLUGIN_README: &str = include_str!("../../assets/default-plugin-project/README.md");
static PLUGIN_GIT_IGNORE: &str = include_str!("../../assets/default-plugin-project/gitignore.txt");

/// Initializes a new Rojo project.
#[derive(Debug, Parser)]
pub struct InitCommand {
    /// Path to the place to create the project. Defaults to the current directory.
    #[clap(default_value = "")]
    pub path: PathBuf,

    /// The kind of project to create, 'place', 'plugin', or 'model'. Defaults to place.
    #[clap(long, default_value = "place")]
    pub kind: InitKind,
}

impl InitCommand {
    pub fn run(self) -> anyhow::Result<()> {
        let base_path = resolve_path(&self.path);
        fs::create_dir_all(&base_path)?;

        let canonical = fs::canonicalize(&base_path)?;
        let project_name = canonical
            .file_name()
            .and_then(|name| name.to_str())
            .unwrap_or("new-project");

        let project_params = ProjectParams {
            name: project_name.to_owned(),
        };

        match self.kind {
            InitKind::Place => init_place(&base_path, project_params)?,
            InitKind::Model => init_model(&base_path, project_params)?,
            InitKind::Plugin => init_plugin(&base_path, project_params)?,
        }

        println!("Created project successfully.");

        Ok(())
    }
}

/// The templates we support for initializing a Rojo project.
#[derive(Debug, Clone, Copy)]
pub enum InitKind {
    /// A place that contains a baseplate.
    Place,

    /// An empty model, suitable for a library.
    Model,

    /// An empty plugin.
    Plugin,
}

impl FromStr for InitKind {
    type Err = anyhow::Error;

    fn from_str(source: &str) -> Result<Self, Self::Err> {
        match source {
            "place" => Ok(InitKind::Place),
            "model" => Ok(InitKind::Model),
            "plugin" => Ok(InitKind::Plugin),
            _ => Err(format_err!(
                "Invalid init kind '{}'. Valid kinds are: place, model, plugin",
                source
            )),
        }
    }
}

fn init_place(base_path: &Path, project_params: ProjectParams) -> anyhow::Result<()> {
    println!("Creating new place project '{}'", project_params.name);

    let project_file = project_params.render_template(PLACE_PROJECT);
    try_create_project(base_path, &project_file)?;

    let readme = project_params.render_template(PLACE_README);
    write_if_not_exists(&base_path.join("README.md"), &readme)?;

    let src = base_path.join("src");
    fs::create_dir_all(&src)?;

    let src_shared = src.join("shared");
    fs::create_dir_all(src.join(&src_shared))?;

    let src_server = src.join("server");
    fs::create_dir_all(src.join(&src_server))?;

    let src_client = src.join("client");
    fs::create_dir_all(src.join(&src_client))?;

    write_if_not_exists(
        &src_shared.join("Hello.luau"),
        "return function()\n\tprint(\"Hello, world!\")\nend",
    )?;

    write_if_not_exists(
        &src_server.join("init.server.luau"),
        "print(\"Hello world, from server!\")",
    )?;

    write_if_not_exists(
        &src_client.join("init.client.luau"),
        "print(\"Hello world, from client!\")",
    )?;

    let git_ignore = project_params.render_template(PLACE_GIT_IGNORE);
    try_git_init(base_path, &git_ignore)?;

    Ok(())
}

fn init_model(base_path: &Path, project_params: ProjectParams) -> anyhow::Result<()> {
    println!("Creating new model project '{}'", project_params.name);

    let project_file = project_params.render_template(MODEL_PROJECT);
    try_create_project(base_path, &project_file)?;

    let readme = project_params.render_template(MODEL_README);
    write_if_not_exists(&base_path.join("README.md"), &readme)?;

    let src = base_path.join("src");
    fs::create_dir_all(&src)?;

    let init = project_params.render_template(MODEL_INIT);
    write_if_not_exists(&src.join("init.luau"), &init)?;

    let git_ignore = project_params.render_template(MODEL_GIT_IGNORE);
    try_git_init(base_path, &git_ignore)?;

    Ok(())
}

fn init_plugin(base_path: &Path, project_params: ProjectParams) -> anyhow::Result<()> {
    println!("Creating new plugin project '{}'", project_params.name);

    let project_file = project_params.render_template(PLUGIN_PROJECT);
    try_create_project(base_path, &project_file)?;

    let readme = project_params.render_template(PLUGIN_README);
    write_if_not_exists(&base_path.join("README.md"), &readme)?;

    let src = base_path.join("src");
    fs::create_dir_all(&src)?;

    write_if_not_exists(
        &src.join("init.server.luau"),
        "print(\"Hello world, from plugin!\")\n",
    )?;

    let git_ignore = project_params.render_template(PLUGIN_GIT_IGNORE);
    try_git_init(base_path, &git_ignore)?;

    Ok(())
}

/// Contains parameters used in templates to create a project.
struct ProjectParams {
    name: String,
}

impl ProjectParams {
    /// Render a template by replacing variables with project parameters.
    fn render_template(&self, template: &str) -> String {
        template
            .replace("{project_name}", &self.name)
            .replace("{rojo_version}", env!("CARGO_PKG_VERSION"))
    }
}

/// Attempt to initialize a Git repository if necessary, and create .gitignore.
fn try_git_init(path: &Path, git_ignore: &str) -> Result<(), anyhow::Error> {
    if should_git_init(path) {
        log::debug!("Initializing Git repository...");

        let status = Command::new("git").arg("init").current_dir(path).status()?;

        if !status.success() {
            bail!("git init failed: status code {:?}", status.code());
        }
    }

    write_if_not_exists(&path.join(".gitignore"), git_ignore)?;

    Ok(())
}

/// Tells whether we should initialize a Git repository inside the given path.
///
/// Will return false if the user doesn't have Git installed or if the path is
/// already inside a Git repository.
fn should_git_init(path: &Path) -> bool {
    let result = Command::new("git")
        .args(["rev-parse", "--is-inside-work-tree"])
        .stdout(Stdio::null())
        .stderr(Stdio::null())
        .current_dir(path)
        .status();

    match result {
        // If the command ran, but returned a non-zero exit code, we are not in
        // a Git repo and we should initialize one.
        Ok(status) => !status.success(),

        // If the command failed to run, we probably don't have Git installed.
        Err(_) => false,
    }
}

/// Write a file if it does not exist yet, otherwise, leave it alone.
fn write_if_not_exists(path: &Path, contents: &str) -> Result<(), anyhow::Error> {
    let file_res = OpenOptions::new().write(true).create_new(true).open(path);

    let mut file = match file_res {
        Ok(file) => file,
        Err(err) => {
            return match err.kind() {
                io::ErrorKind::AlreadyExists => return Ok(()),
                _ => Err(err.into()),
            }
        }
    };

    file.write_all(contents.as_bytes())?;

    Ok(())
}

/// Try to create a project file and fail if it already exists.
fn try_create_project(base_path: &Path, contents: &str) -> Result<(), anyhow::Error> {
    let project_path = base_path.join("default.project.json");

    let file_res = OpenOptions::new()
        .write(true)
        .create_new(true)
        .open(&project_path);

    let mut file = match file_res {
        Ok(file) => file,
        Err(err) => {
            return match err.kind() {
                io::ErrorKind::AlreadyExists => {
                    bail!("Project file already exists: {}", project_path.display())
                }
                _ => Err(err.into()),
            }
        }
    };

    file.write_all(contents.as_bytes())?;

    Ok(())
}