// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
//! This module is meant to eventually implement HTTP cache
//! as defined in RFC 7234 (<https://tools.ietf.org/html/rfc7234>).
//! Currently it's a very simplified version to fulfill Deno needs
//! at hand.
use crate::http_util::HeadersMap;
use crate::util;
use deno_core::error::generic_error;
use deno_core::error::AnyError;
use deno_core::serde::Deserialize;
use deno_core::serde::Serialize;
use deno_core::serde_json;
use deno_core::url::Url;
use std::fs;
use std::io;
use std::path::Path;
use std::path::PathBuf;
use std::time::SystemTime;

use super::CACHE_PERM;

/// Turn base of url (scheme, hostname, port) into a valid filename.
/// This method replaces port part with a special string token (because
/// ":" cannot be used in filename on some platforms).
/// Ex: $DENO_DIR/deps/https/deno.land/
fn base_url_to_filename(url: &Url) -> Option<PathBuf> {
  let mut out = PathBuf::new();

  let scheme = url.scheme();
  out.push(scheme);

  match scheme {
    "http" | "https" => {
      let host = url.host_str().unwrap();
      let host_port = match url.port() {
        Some(port) => format!("{host}_PORT{port}"),
        None => host.to_string(),
      };
      out.push(host_port);
    }
    "data" | "blob" => (),
    scheme => {
      log::debug!("Don't know how to create cache name for scheme: {}", scheme);
      return None;
    }
  };

  Some(out)
}

/// Turn provided `url` into a hashed filename.
/// URLs can contain a lot of characters that cannot be used
/// in filenames (like "?", "#", ":"), so in order to cache
/// them properly they are deterministically hashed into ASCII
/// strings.
///
/// NOTE: this method is `pub` because it's used in integration_tests
pub fn url_to_filename(url: &Url) -> Option<PathBuf> {
  let mut cache_filename = base_url_to_filename(url)?;

  let mut rest_str = url.path().to_string();
  if let Some(query) = url.query() {
    rest_str.push('?');
    rest_str.push_str(query);
  }
  // NOTE: fragment is omitted on purpose - it's not taken into
  // account when caching - it denotes parts of webpage, which
  // in case of static resources doesn't make much sense
  let hashed_filename = util::checksum::gen(&[rest_str.as_bytes()]);
  cache_filename.push(hashed_filename);
  Some(cache_filename)
}

/// Cached metadata about a url.
#[derive(Debug, Serialize, Deserialize, PartialEq, Eq)]
pub struct CachedUrlMetadata {
  pub headers: HeadersMap,
  pub url: String,
  #[serde(default = "SystemTime::now", rename = "now")]
  pub time: SystemTime,
}

// DO NOT make the path public. The fact that this is stored in a file
// is an implementation detail.
pub struct MaybeHttpCacheItem(PathBuf);

impl MaybeHttpCacheItem {
  #[cfg(test)]
  pub fn read_to_string(&self) -> Result<Option<String>, AnyError> {
    let Some(bytes) = self.read_to_bytes()? else {
      return Ok(None);
    };
    Ok(Some(String::from_utf8(bytes)?))
  }

  pub fn read_to_bytes(&self) -> Result<Option<Vec<u8>>, AnyError> {
    match std::fs::read(&self.0) {
      Ok(s) => Ok(Some(s)),
      Err(err) if err.kind() == std::io::ErrorKind::NotFound => Ok(None),
      Err(err) => Err(err.into()),
    }
  }

  pub fn read_metadata(&self) -> Result<Option<CachedUrlMetadata>, AnyError> {
    let metadata_filepath = self.0.with_extension("metadata.json");
    match fs::read_to_string(metadata_filepath) {
      Ok(metadata) => Ok(Some(serde_json::from_str(&metadata)?)),
      Err(err) if err.kind() == std::io::ErrorKind::NotFound => Ok(None),
      Err(err) => Err(err.into()),
    }
  }
}

#[derive(Debug, Clone, Default)]
pub struct HttpCache {
  pub location: PathBuf,
}

impl HttpCache {
  /// Returns a new instance.
  ///
  /// `location` must be an absolute path.
  pub fn new(location: PathBuf) -> Self {
    assert!(location.is_absolute());
    Self { location }
  }

  /// Ensures the location of the cache.
  fn ensure_dir_exists(&self, path: &Path) -> io::Result<()> {
    if path.is_dir() {
      return Ok(());
    }
    fs::create_dir_all(path).map_err(|e| {
      io::Error::new(
        e.kind(),
        format!(
          "Could not create remote modules cache location: {path:?}\nCheck the permission of the directory."
        ),
      )
    })
  }

  pub fn get_modified_time(
    &self,
    url: &Url,
  ) -> Result<Option<SystemTime>, AnyError> {
    let filepath = self.get_cache_filepath_internal(url)?;
    match fs::metadata(filepath) {
      Ok(metadata) => Ok(Some(metadata.modified()?)),
      Err(err) if err.kind() == io::ErrorKind::NotFound => Ok(None),
      Err(err) => Err(err.into()),
    }
  }

  // DEPRECATED: Where the file is stored and how it's stored should be an implementation
  // detail of the cache.
  #[deprecated(note = "Do not assume the cache will be stored at a file path.")]
  pub fn get_cache_filepath(&self, url: &Url) -> Result<PathBuf, AnyError> {
    self.get_cache_filepath_internal(url)
  }

  fn get_cache_filepath_internal(
    &self,
    url: &Url,
  ) -> Result<PathBuf, AnyError> {
    Ok(
      self.location.join(
        url_to_filename(url)
          .ok_or_else(|| generic_error("Can't convert url to filename."))?,
      ),
    )
  }

  #[cfg(test)]
  pub fn write_metadata(
    &self,
    url: &Url,
    meta_data: &CachedUrlMetadata,
  ) -> Result<(), AnyError> {
    let cache_path = self.get_cache_filepath_internal(url)?;
    self.write_metadata_at_path(&cache_path, meta_data)
  }

  fn write_metadata_at_path(
    &self,
    path: &Path,
    meta_data: &CachedUrlMetadata,
  ) -> Result<(), AnyError> {
    let cache_path = path.with_extension("metadata.json");
    let json = serde_json::to_string_pretty(meta_data)?;
    util::fs::atomic_write_file(&cache_path, json, CACHE_PERM)?;
    Ok(())
  }

  // TODO(bartlomieju): this method should check headers file
  // and validate against ETAG/Last-modified-as headers.
  // ETAG check is currently done in `cli/file_fetcher.rs`.
  pub fn get(&self, url: &Url) -> Result<MaybeHttpCacheItem, AnyError> {
    let cache_filepath = self.get_cache_filepath_internal(url)?;
    Ok(MaybeHttpCacheItem(cache_filepath))
  }

  pub fn set(
    &self,
    url: &Url,
    headers_map: HeadersMap,
    content: &[u8],
  ) -> Result<(), AnyError> {
    let cache_filepath = self.get_cache_filepath_internal(url)?;
    // Create parent directory
    let parent_filename = cache_filepath
      .parent()
      .expect("Cache filename should have a parent dir");
    self.ensure_dir_exists(parent_filename)?;
    // Cache content
    util::fs::atomic_write_file(&cache_filepath, content, CACHE_PERM)?;

    let metadata = CachedUrlMetadata {
      time: SystemTime::now(),
      url: url.to_string(),
      headers: headers_map,
    };
    self.write_metadata_at_path(&cache_filepath, &metadata)?;

    Ok(())
  }

  pub fn contains(&self, url: &Url) -> bool {
    let Ok(cache_filepath) = self.get_cache_filepath_internal(url) else {
      return false
    };
    cache_filepath.is_file()
  }
}

#[cfg(test)]
mod tests {
  use super::*;
  use std::collections::HashMap;
  use test_util::TempDir;

  #[test]
  fn test_create_cache() {
    let dir = TempDir::new();
    let cache_path = dir.path().join("foobar");
    // HttpCache should be created lazily on first use:
    // when zipping up a local project with no external dependencies
    // "$DENO_DIR/deps" is empty. When unzipping such project
    // "$DENO_DIR/deps" might not get restored and in situation
    // when directory is owned by root we might not be able
    // to create that directory. However if it's not needed it
    // doesn't make sense to return error in such specific scenarios.
    // For more details check issue:
    // https://github.com/denoland/deno/issues/5688
    let cache = HttpCache::new(cache_path.to_path_buf());
    assert!(!cache.location.exists());
    cache
      .set(
        &Url::parse("http://example.com/foo/bar.js").unwrap(),
        HeadersMap::new(),
        b"hello world",
      )
      .expect("Failed to add to cache");
    assert!(cache.ensure_dir_exists(&cache.location).is_ok());
    assert!(cache_path.is_dir());
  }

  #[test]
  fn test_get_set() {
    let dir = TempDir::new();
    let cache = HttpCache::new(dir.path().to_path_buf());
    let url = Url::parse("https://deno.land/x/welcome.ts").unwrap();
    let mut headers = HashMap::new();
    headers.insert(
      "content-type".to_string(),
      "application/javascript".to_string(),
    );
    headers.insert("etag".to_string(), "as5625rqdsfb".to_string());
    let content = b"Hello world";
    let r = cache.set(&url, headers, content);
    eprintln!("result {r:?}");
    assert!(r.is_ok());
    let cache_item = cache.get(&url).unwrap();
    let content = cache_item.read_to_string().unwrap().unwrap();
    let headers = cache_item.read_metadata().unwrap().unwrap().headers;
    assert_eq!(content, "Hello world");
    assert_eq!(
      headers.get("content-type").unwrap(),
      "application/javascript"
    );
    assert_eq!(headers.get("etag").unwrap(), "as5625rqdsfb");
    assert_eq!(headers.get("foobar"), None);
  }

  #[test]
  fn test_url_to_filename() {
    let test_cases = [
      ("https://deno.land/x/foo.ts", "https/deno.land/2c0a064891b9e3fbe386f5d4a833bce5076543f5404613656042107213a7bbc8"),
      (
        "https://deno.land:8080/x/foo.ts",
        "https/deno.land_PORT8080/2c0a064891b9e3fbe386f5d4a833bce5076543f5404613656042107213a7bbc8",
      ),
      ("https://deno.land/", "https/deno.land/8a5edab282632443219e051e4ade2d1d5bbc671c781051bf1437897cbdfea0f1"),
      (
        "https://deno.land/?asdf=qwer",
        "https/deno.land/e4edd1f433165141015db6a823094e6bd8f24dd16fe33f2abd99d34a0a21a3c0",
      ),
      // should be the same as case above, fragment (#qwer) is ignored
      // when hashing
      (
        "https://deno.land/?asdf=qwer#qwer",
        "https/deno.land/e4edd1f433165141015db6a823094e6bd8f24dd16fe33f2abd99d34a0a21a3c0",
      ),
      (
        "data:application/typescript;base64,ZXhwb3J0IGNvbnN0IGEgPSAiYSI7CgpleHBvcnQgZW51bSBBIHsKICBBLAogIEIsCiAgQywKfQo=",
        "data/c21c7fc382b2b0553dc0864aa81a3acacfb7b3d1285ab5ae76da6abec213fb37",
      ),
      (
        "data:text/plain,Hello%2C%20Deno!",
        "data/967374e3561d6741234131e342bf5c6848b70b13758adfe23ee1a813a8131818",
      )
    ];

    for (url, expected) in test_cases.iter() {
      let u = Url::parse(url).unwrap();
      let p = url_to_filename(&u).unwrap();
      assert_eq!(p, PathBuf::from(expected));
    }
  }
}