From ce9a148940648f9d50ee8b11fa31e222bd336e27 Mon Sep 17 00:00:00 2001
From: Tom Bereknyei <tomberek@gmail.com>
Date: Sun, 13 Feb 2022 11:52:21 -0500
Subject: [PATCH] fetchers: able to fetch a single remote file instead of a
 tree

---
 src/libfetchers/url.cc | 133 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 133 insertions(+)
 create mode 100644 src/libfetchers/url.cc

diff --git a/src/libfetchers/url.cc b/src/libfetchers/url.cc
new file mode 100644
index 000000000..6bb9e1770
--- /dev/null
+++ b/src/libfetchers/url.cc
@@ -0,0 +1,133 @@
+#include "fetchers.hh"
+#include "cache.hh"
+#include "filetransfer.hh"
+#include "globals.hh"
+#include "store-api.hh"
+#include "archive.hh"
+#include "tarfile.hh"
+#include "types.hh"
+
+namespace nix::fetchers {
+
+std::pair<Tree, time_t> downloadRawFile(
+    ref<Store> store,
+    const std::string & url,
+    const std::string & name,
+    bool immutable,
+    const Headers & headers)
+{
+    Attrs inAttrs({
+        {"type", "url"},
+        {"url", url},
+        {"name", name},
+    });
+
+    auto cached = getCache()->lookupExpired(store, inAttrs);
+
+    if (cached && !cached->expired)
+        return {
+            Tree(store->toRealPath(cached->storePath), std::move(cached->storePath)),
+            getIntAttr(cached->infoAttrs, "lastModified")
+        };
+
+    auto res = downloadFile(store, url, name, immutable, headers);
+
+    std::optional<StorePath> unpackedStorePath;
+    time_t lastModified;
+
+    if (cached && res.etag != "" && getStrAttr(cached->infoAttrs, "etag") == res.etag) {
+        unpackedStorePath = std::move(cached->storePath);
+        lastModified = getIntAttr(cached->infoAttrs, "lastModified");
+    } else {
+        lastModified = lstat(store->toRealPath(cached->storePath)).st_mtime;
+    }
+
+    Attrs infoAttrs({
+        {"lastModified", uint64_t(lastModified)},
+        {"etag", res.etag},
+    });
+
+    getCache()->add(
+        store,
+        inAttrs,
+        infoAttrs,
+        res.storePath,
+        immutable);
+
+    return {
+        Tree(store->toRealPath(*unpackedStorePath), std::move(*unpackedStorePath)),
+        lastModified,
+    };
+}
+
+struct UrlInputScheme : InputScheme
+{
+    std::optional<Input> inputFromURL(const ParsedURL & url) override
+    {
+        if (url.scheme != "file" && url.scheme != "http" && url.scheme != "https") return {};
+
+        if (hasSuffix(url.path, ".zip")
+            || hasSuffix(url.path, ".tar")
+            || hasSuffix(url.path, ".tgz")
+            || hasSuffix(url.path, ".tar.gz")
+            || hasSuffix(url.path, ".tar.xz")
+            || hasSuffix(url.path, ".tar.bz2")
+            || hasSuffix(url.path, ".tar.zst"))
+            return {};
+
+        Input input;
+        input.attrs.insert_or_assign("type", "url");
+        input.attrs.insert_or_assign("flake", false);
+        input.attrs.insert_or_assign("url", url.to_string());
+        auto narHash = url.query.find("narHash");
+        if (narHash != url.query.end())
+            input.attrs.insert_or_assign("narHash", narHash->second);
+        return input;
+    }
+
+    std::optional<Input> inputFromAttrs(const Attrs & attrs) override
+    {
+        if (maybeGetStrAttr(attrs, "type") != "url") return {};
+
+        for (auto & [name, value] : attrs)
+            if (name != "type" && name != "url" && name != "flake" && name != "narHash" && name != "name")
+                throw Error("unsupported url input attribute '%s'", name);
+
+        Input input;
+        input.attrs = attrs;
+        //input.immutable = (bool) maybeGetStrAttr(input.attrs, "hash");
+        return input;
+    }
+
+    ParsedURL toURL(const Input & input) override
+    {
+        auto url = parseURL(getStrAttr(input.attrs, "url"));
+        // NAR hashes are preferred over file hashes since tar/zip files
+        // don't have a canonical representation.
+        if (auto narHash = input.getNarHash())
+            url.query.insert_or_assign("narHash", narHash->to_string(SRI, true));
+        /*
+        else if (auto hash = maybeGetStrAttr(input.attrs, "hash"))
+            url.query.insert_or_assign("hash", Hash(*hash).to_string(SRI, true));
+        */
+        return url;
+    }
+
+    bool hasAllInfo(const Input & input) override
+    {
+        return true;
+    }
+
+    std::pair<Tree, Input> fetch(ref<Store> store, const Input & input) override
+    {
+        auto tree = downloadFile(store, getStrAttr(input.attrs, "url"), input.getName(), false);
+        return {
+            Tree(store->toRealPath(tree.storePath), std::move(tree.storePath)),
+            input,
+        };
+    }
+};
+
+static auto rUrlInputScheme = OnStartup([] { registerInputScheme(std::make_unique<UrlInputScheme>()); });
+
+}