use crate::colors;
use crate::flags::DenoSubcommand;
use crate::flags::Flags;
use crate::tokio_util;
use crate::version;
use deno_core::error::bail;
use deno_core::error::type_error;
use deno_core::error::AnyError;
use deno_core::error::Context;
use deno_core::futures::FutureExt;
use deno_core::serde::Deserialize;
use deno_core::serde::Serialize;
use deno_core::serde_json;
use deno_core::v8_set_flags;
use deno_core::ModuleLoader;
use deno_core::ModuleSpecifier;
use deno_core::OpState;
use deno_runtime::permissions::Permissions;
use deno_runtime::worker::MainWorker;
use deno_runtime::worker::WorkerOptions;
use std::cell::RefCell;
use std::convert::TryInto;
use std::env::current_exe;
use std::fs::read;
use std::fs::File;
use std::io::Read;
use std::io::Seek;
use std::io::SeekFrom;
use std::io::Write;
use std::iter::once;
use std::path::PathBuf;
use std::pin::Pin;
use std::rc::Rc;
use std::sync::Arc;

#[derive(Deserialize, Serialize)]
struct Metadata {
  flags: Flags,
  ca_data: Option<Vec<u8>>,
}

const MAGIC_TRAILER: &[u8; 8] = b"d3n0l4nd";

/// This function will try to run this binary as a standalone binary
/// produced by `deno compile`. It determines if this is a stanalone
/// binary by checking for the magic trailer string `D3N0` at EOF-12.
/// The magic trailer is followed by:
/// - a u64 pointer to the JS bundle embedded in the binary
/// - a u64 pointer to JSON metadata (serialized flags) embedded in the binary
/// These are dereferenced, and the bundle is executed under the configuration
/// specified by the metadata. If no magic trailer is present, this function
/// exits with `Ok(())`.
pub fn try_run_standalone_binary(args: Vec<String>) -> Result<(), AnyError> {
  let current_exe_path = current_exe()?;

  let mut current_exe = File::open(current_exe_path)?;
  let trailer_pos = current_exe.seek(SeekFrom::End(-24))?;
  let mut trailer = [0; 24];
  current_exe.read_exact(&mut trailer)?;
  let (magic_trailer, rest) = trailer.split_at(8);
  if magic_trailer == MAGIC_TRAILER {
    let (bundle_pos, rest) = rest.split_at(8);
    let metadata_pos = rest;
    let bundle_pos = u64_from_bytes(bundle_pos)?;
    let metadata_pos = u64_from_bytes(metadata_pos)?;
    let bundle_len = metadata_pos - bundle_pos;
    let metadata_len = trailer_pos - metadata_pos;
    current_exe.seek(SeekFrom::Start(bundle_pos))?;

    let bundle = read_string_slice(&mut current_exe, bundle_pos, bundle_len)
      .context("Failed to read source bundle from the current executable")?;
    let metadata =
      read_string_slice(&mut current_exe, metadata_pos, metadata_len)
        .context("Failed to read metadata from the current executable")?;

    let mut metadata: Metadata = serde_json::from_str(&metadata).unwrap();
    metadata.flags.argv.append(&mut args[1..].to_vec());
    if let Err(err) = tokio_util::run_basic(run(bundle, metadata)) {
      eprintln!("{}: {}", colors::red_bold("error"), err.to_string());
      std::process::exit(1);
    }
    std::process::exit(0);
  } else {
    Ok(())
  }
}

fn u64_from_bytes(arr: &[u8]) -> Result<u64, AnyError> {
  let fixed_arr: &[u8; 8] = arr
    .try_into()
    .context("Failed to convert the buffer into a fixed-size array")?;
  Ok(u64::from_be_bytes(*fixed_arr))
}

fn read_string_slice(
  file: &mut File,
  pos: u64,
  len: u64,
) -> Result<String, AnyError> {
  let mut string = String::new();
  file.seek(SeekFrom::Start(pos))?;
  file.take(len).read_to_string(&mut string)?;
  // TODO: check amount of bytes read
  Ok(string)
}

const SPECIFIER: &str = "file://$deno$/bundle.js";

struct EmbeddedModuleLoader(String);

impl ModuleLoader for EmbeddedModuleLoader {
  fn resolve(
    &self,
    _op_state: Rc<RefCell<OpState>>,
    specifier: &str,
    _referrer: &str,
    _is_main: bool,
  ) -> Result<ModuleSpecifier, AnyError> {
    if specifier != SPECIFIER {
      return Err(type_error(
        "Self-contained binaries don't support module loading",
      ));
    }
    Ok(ModuleSpecifier::resolve_url(specifier)?)
  }

  fn load(
    &self,
    _op_state: Rc<RefCell<OpState>>,
    module_specifier: &ModuleSpecifier,
    _maybe_referrer: Option<ModuleSpecifier>,
    _is_dynamic: bool,
  ) -> Pin<Box<deno_core::ModuleSourceFuture>> {
    let module_specifier = module_specifier.clone();
    let code = self.0.to_string();
    async move {
      if module_specifier.to_string() != SPECIFIER {
        return Err(type_error(
          "Self-contained binaries don't support module loading",
        ));
      }
      Ok(deno_core::ModuleSource {
        code,
        module_url_specified: module_specifier.to_string(),
        module_url_found: module_specifier.to_string(),
      })
    }
    .boxed_local()
  }
}

async fn run(source_code: String, metadata: Metadata) -> Result<(), AnyError> {
  let Metadata { flags, ca_data } = metadata;
  let main_module = ModuleSpecifier::resolve_url(SPECIFIER)?;
  let permissions = Permissions::from_options(&flags.clone().into());
  let module_loader = Rc::new(EmbeddedModuleLoader(source_code));
  let create_web_worker_cb = Arc::new(|_| {
    todo!("Worker are currently not supported in standalone binaries");
  });

  // Keep in sync with `main.rs`.
  v8_set_flags(
    once("UNUSED_BUT_NECESSARY_ARG0".to_owned())
      .chain(flags.v8_flags.iter().cloned())
      .collect::<Vec<_>>(),
  );
  // TODO(nayeemrmn): Unify this Flags -> WorkerOptions mapping with `deno run`.
  let options = WorkerOptions {
    apply_source_maps: false,
    args: flags.argv.clone(),
    debug_flag: flags.log_level.map_or(false, |l| l == log::Level::Debug),
    user_agent: crate::http_util::get_user_agent(),
    unstable: flags.unstable,
    ca_data,
    seed: flags.seed,
    js_error_create_fn: None,
    create_web_worker_cb,
    attach_inspector: false,
    maybe_inspector_server: None,
    should_break_on_first_statement: false,
    module_loader,
    runtime_version: version::deno(),
    ts_version: version::TYPESCRIPT.to_string(),
    no_color: !colors::use_color(),
    get_error_class_fn: Some(&crate::errors::get_error_class_name),
  };
  let mut worker =
    MainWorker::from_options(main_module.clone(), permissions, &options);
  worker.bootstrap(&options);
  worker.execute_module(&main_module).await?;
  worker.execute("window.dispatchEvent(new Event('load'))")?;
  worker.run_event_loop().await?;
  worker.execute("window.dispatchEvent(new Event('unload'))")?;
  Ok(())
}

/// This functions creates a standalone deno binary by appending a bundle
/// and magic trailer to the currently executing binary.
pub async fn create_standalone_binary(
  source_code: String,
  flags: Flags,
  output: PathBuf,
) -> Result<(), AnyError> {
  let mut source_code = source_code.as_bytes().to_vec();
  let ca_data = match &flags.ca_file {
    Some(ca_file) => Some(read(ca_file)?),
    None => None,
  };
  let metadata = Metadata { flags, ca_data };
  let mut metadata = serde_json::to_string(&metadata)?.as_bytes().to_vec();
  let original_binary_path = std::env::current_exe()?;
  let mut original_bin = tokio::fs::read(original_binary_path).await?;

  let bundle_pos = original_bin.len();
  let metadata_pos = bundle_pos + source_code.len();
  let mut trailer = MAGIC_TRAILER.to_vec();
  trailer.write_all(&bundle_pos.to_be_bytes())?;
  trailer.write_all(&metadata_pos.to_be_bytes())?;

  let mut final_bin =
    Vec::with_capacity(original_bin.len() + source_code.len() + trailer.len());
  final_bin.append(&mut original_bin);
  final_bin.append(&mut source_code);
  final_bin.append(&mut metadata);
  final_bin.append(&mut trailer);

  let output =
    if cfg!(windows) && output.extension().unwrap_or_default() != "exe" {
      PathBuf::from(output.display().to_string() + ".exe")
    } else {
      output
    };

  if output.exists() {
    // If the output is a directory, throw error
    if output.is_dir() {
      bail!("Could not compile: {:?} is a directory.", &output);
    }

    // Make sure we don't overwrite any file not created by Deno compiler.
    // Check for magic trailer in last 24 bytes.
    let mut has_trailer = false;
    let mut output_file = File::open(&output)?;
    // This seek may fail because the file is too small to possibly be
    // `deno compile` output.
    if output_file.seek(SeekFrom::End(-24)).is_ok() {
      let mut trailer = [0; 24];
      output_file.read_exact(&mut trailer)?;
      let (magic_trailer, _) = trailer.split_at(8);
      has_trailer = magic_trailer == MAGIC_TRAILER;
    }
    if !has_trailer {
      bail!("Could not compile: cannot overwrite {:?}.", &output);
    }
  }
  tokio::fs::write(&output, final_bin).await?;
  #[cfg(unix)]
  {
    use std::os::unix::fs::PermissionsExt;
    let perms = std::fs::Permissions::from_mode(0o777);
    tokio::fs::set_permissions(output, perms).await?;
  }

  Ok(())
}

/// Transform the flags passed to `deno compile` to flags that would be used at
/// runtime, as if `deno run` were used.
/// - Flags that affect module resolution, loading, type checking, etc. aren't
///   applicable at runtime so are set to their defaults like `false`.
/// - Other flags are inherited.
pub fn compile_to_runtime_flags(
  flags: Flags,
  baked_args: Vec<String>,
) -> Result<Flags, AnyError> {
  // IMPORTANT: Don't abbreviate any of this to `..flags` or
  // `..Default::default()`. That forces us to explicitly consider how any
  // change to `Flags` should be reflected here.
  Ok(Flags {
    argv: baked_args,
    subcommand: DenoSubcommand::Run {
      script: "placeholder".to_string(),
    },
    allow_env: flags.allow_env,
    allow_hrtime: flags.allow_hrtime,
    allow_net: flags.allow_net,
    allow_plugin: flags.allow_plugin,
    allow_read: flags.allow_read,
    allow_run: flags.allow_run,
    allow_write: flags.allow_write,
    cache_blocklist: vec![],
    ca_file: flags.ca_file,
    cached_only: false,
    config_path: None,
    coverage_dir: flags.coverage_dir,
    ignore: vec![],
    import_map_path: None,
    inspect: None,
    inspect_brk: None,
    lock: None,
    lock_write: false,
    log_level: flags.log_level,
    no_check: false,
    no_prompts: flags.no_prompts,
    no_remote: false,
    reload: false,
    repl: false,
    seed: flags.seed,
    unstable: flags.unstable,
    v8_flags: flags.v8_flags,
    version: false,
    watch: false,
  })
}