1 files changed, 152 insertions, 0 deletions
diff --git a/cli/http_util.rs b/cli/http_util.rs
index 87ed7d598..562cd06f2 100644
--- a/cli/http_util.rs
+++ b/cli/http_util.rs
@@ -1,6 +1,9 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 use crate::auth_tokens::AuthToken;
 
+use cache_control::Cachability;
+use cache_control::CacheControl;
+use chrono::DateTime;
 use deno_core::error::custom_error;
 use deno_core::error::generic_error;
 use deno_core::error::AnyError;
@@ -13,6 +16,8 @@ use deno_runtime::deno_fetch::reqwest::Client;
 use deno_runtime::deno_fetch::reqwest::StatusCode;
 use log::debug;
 use std::collections::HashMap;
+use std::time::Duration;
+use std::time::SystemTime;
 
 /// Construct the next uri based on base uri and location header fragment
 /// See <https://tools.ietf.org/html/rfc3986#section-4.2>
@@ -46,6 +51,153 @@ fn resolve_url_from_location(base_url: &Url, location: &str) -> Url {
 // Vec<(String, String)>
 pub type HeadersMap = HashMap<String, String>;
 
+/// A structure used to determine if a entity in the http cache can be used.
+///
+/// This is heavily influenced by
+/// https://github.com/kornelski/rusty-http-cache-semantics which is BSD
+/// 2-Clause Licensed and copyright Kornel Lesiński
+pub(crate) struct CacheSemantics {
+  cache_control: CacheControl,
+  cached: SystemTime,
+  headers: HashMap<String, String>,
+  now: SystemTime,
+}
+
+impl CacheSemantics {
+  pub fn new(
+    headers: HashMap<String, String>,
+    cached: SystemTime,
+    now: SystemTime,
+  ) -> Self {
+    let cache_control = headers
+      .get("cache-control")
+      .map(|v| CacheControl::from_value(v).unwrap_or_default())
+      .unwrap_or_default();
+    Self {
+      cache_control,
+      cached,
+      headers,
+      now,
+    }
+  }
+
+  fn age(&self) -> Duration {
+    let mut age = self.age_header_value();
+
+    if let Ok(resident_time) = self.now.duration_since(self.cached) {
+      age += resident_time;
+    }
+
+    age
+  }
+
+  fn age_header_value(&self) -> Duration {
+    Duration::from_secs(
+      self
+        .headers
+        .get("age")
+        .and_then(|v| v.parse().ok())
+        .unwrap_or(0),
+    )
+  }
+
+  fn is_stale(&self) -> bool {
+    self.max_age() <= self.age()
+  }
+
+  fn max_age(&self) -> Duration {
+    if self.cache_control.cachability == Some(Cachability::NoCache) {
+      return Duration::from_secs(0);
+    }
+
+    if self.headers.get("vary").map(|s| s.trim()) == Some("*") {
+      return Duration::from_secs(0);
+    }
+
+    if let Some(max_age) = self.cache_control.max_age {
+      return max_age;
+    }
+
+    let default_min_ttl = Duration::from_secs(0);
+
+    let server_date = self.raw_server_date();
+    if let Some(expires) = self.headers.get("expires") {
+      return match DateTime::parse_from_rfc2822(expires) {
+        Err(_) => Duration::from_secs(0),
+        Ok(expires) => {
+          let expires = SystemTime::UNIX_EPOCH
+            + Duration::from_secs(expires.timestamp().max(0) as _);
+          return default_min_ttl
+            .max(expires.duration_since(server_date).unwrap_or_default());
+        }
+      };
+    }
+
+    if let Some(last_modified) = self.headers.get("last-modified") {
+      if let Ok(last_modified) = DateTime::parse_from_rfc2822(last_modified) {
+        let last_modified = SystemTime::UNIX_EPOCH
+          + Duration::from_secs(last_modified.timestamp().max(0) as _);
+        if let Ok(diff) = server_date.duration_since(last_modified) {
+          let secs_left = diff.as_secs() as f64 * 0.1;
+          return default_min_ttl.max(Duration::from_secs(secs_left as _));
+        }
+      }
+    }
+
+    default_min_ttl
+  }
+
+  fn raw_server_date(&self) -> SystemTime {
+    self
+      .headers
+      .get("date")
+      .and_then(|d| DateTime::parse_from_rfc2822(d).ok())
+      .and_then(|d| {
+        SystemTime::UNIX_EPOCH
+          .checked_add(Duration::from_secs(d.timestamp() as _))
+      })
+      .unwrap_or(self.cached)
+  }
+
+  /// Returns true if the cached value is "fresh" respecting cached headers,
+  /// otherwise returns false.
+  pub fn should_use(&self) -> bool {
+    if self.cache_control.cachability == Some(Cachability::NoCache) {
+      return false;
+    }
+
+    if let Some(max_age) = self.cache_control.max_age {
+      if self.age() > max_age {
+        return false;
+      }
+    }
+
+    if let Some(min_fresh) = self.cache_control.min_fresh {
+      if self.time_to_live() < min_fresh {
+        return false;
+      }
+    }
+
+    if self.is_stale() {
+      let has_max_stale = self.cache_control.max_stale.is_some();
+      let allows_stale = has_max_stale
+        && self
+          .cache_control
+          .max_stale
+          .map_or(true, |val| val > self.age() - self.max_age());
+      if !allows_stale {
+        return false;
+      }
+    }
+
+    true
+  }
+
+  fn time_to_live(&self) -> Duration {
+    self.max_age().checked_sub(self.age()).unwrap_or_default()
+  }
+}
+
 #[derive(Debug, PartialEq)]
 pub enum FetchOnceResult {
   Code(Vec<u8>, HeadersMap),