#include "primops.hh"
#include "store-api.hh"
#include "make-content-addressed.hh"
#include "url.hh"

namespace nix {

/**
 * Handler for the content addressed case.
 *
 * @param state Evaluator state and store to write to.
 * @param fromStore Store containing the path to rewrite.
 * @param fromPath Source path to be rewritten.
 * @param toPathMaybe Path to write the rewritten path to. If empty, the error shows the actual path.
 * @param v Return `Value`
 */
static void runFetchClosureWithRewrite(EvalState & state, const PosIdx pos, Store & fromStore, const StorePath & fromPath, const std::optional<StorePath> & toPathMaybe, Value &v) {

    // establish toPath or throw

    if (!toPathMaybe || !state.store->isValidPath(*toPathMaybe)) {
        auto rewrittenPath = makeContentAddressed(fromStore, *state.store, fromPath);
        if (toPathMaybe && *toPathMaybe != rewrittenPath)
            throw Error({
                .msg = hintfmt("rewriting '%s' to content-addressed form yielded '%s', while '%s' was expected",
                    state.store->printStorePath(fromPath),
                    state.store->printStorePath(rewrittenPath),
                    state.store->printStorePath(*toPathMaybe)),
                .errPos = state.positions[pos]
            });
        if (!toPathMaybe)
            throw Error({
                .msg = hintfmt(
                    "rewriting '%s' to content-addressed form yielded '%s'\n"
                    "Use this value for the 'toPath' attribute passed to 'fetchClosure'",
                    state.store->printStorePath(fromPath),
                    state.store->printStorePath(rewrittenPath)),
                .errPos = state.positions[pos]
            });
    }

    auto toPath = *toPathMaybe;

    // check and return

    auto resultInfo = state.store->queryPathInfo(toPath);

    if (!resultInfo->isContentAddressed(*state.store)) {
        // We don't perform the rewriting when outPath already exists, as an optimisation.
        // However, we can quickly detect a mistake if the toPath is input addressed.
        throw Error({
            .msg = hintfmt(
                "The 'toPath' value '%s' is input-addressed, so it can't possibly be the result of rewriting to a content-addressed path.\n\n"
                "Set 'toPath' to an empty string to make Nix report the correct content-addressed path.",
                state.store->printStorePath(toPath)),
            .errPos = state.positions[pos]
        });
    }

    state.mkStorePathString(toPath, v);
}

/**
 * Fetch the closure and make sure it's content addressed.
 */
static void runFetchClosureWithContentAddressedPath(EvalState & state, const PosIdx pos, Store & fromStore, const StorePath & fromPath, Value & v) {

    if (!state.store->isValidPath(fromPath))
        copyClosure(fromStore, *state.store, RealisedPath::Set { fromPath });

    auto info = state.store->queryPathInfo(fromPath);

    if (!info->isContentAddressed(*state.store)) {
        throw Error({
            .msg = hintfmt(
                "The 'fromPath' value '%s' is input-addressed, but 'inputAddressed' is set to 'false' (default).\n\n"
                "If you do intend to fetch an input-addressed store path, add\n\n"
                "    inputAddressed = true;\n\n"
                "to the 'fetchClosure' arguments.\n\n"
                "Note that to ensure authenticity input-addressed store paths, users must configure a trusted binary cache public key on their systems. This is not needed for content-addressed paths.",
                state.store->printStorePath(fromPath)),
            .errPos = state.positions[pos]
        });
    }

    state.mkStorePathString(fromPath, v);
}

/**
 * Fetch the closure and make sure it's input addressed.
 */
static void runFetchClosureWithInputAddressedPath(EvalState & state, const PosIdx pos, Store & fromStore, const StorePath & fromPath, Value & v) {

    if (!state.store->isValidPath(fromPath))
        copyClosure(fromStore, *state.store, RealisedPath::Set { fromPath });

    auto info = state.store->queryPathInfo(fromPath);

    if (info->isContentAddressed(*state.store)) {
        throw Error({
            .msg = hintfmt(
                "The store object referred to by 'fromPath' at '%s' is not input-addressed, but 'inputAddressed' is set to 'true'.\n\n"
                "Remove the 'inputAddressed' attribute (it defaults to 'false') to expect 'fromPath' to be content-addressed",
                state.store->printStorePath(fromPath)),
            .errPos = state.positions[pos]
        });
    }

    state.mkStorePathString(fromPath, v);
}

typedef std::optional<StorePath> StorePathOrGap;

static void prim_fetchClosure(EvalState & state, const PosIdx pos, Value * * args, Value & v)
{
    state.forceAttrs(*args[0], pos, "while evaluating the argument passed to builtins.fetchClosure");

    std::optional<std::string> fromStoreUrl;
    std::optional<StorePath> fromPath;
    std::optional<StorePathOrGap> toPath;
    std::optional<bool> inputAddressedMaybe;

    for (auto & attr : *args[0]->attrs) {
        const auto & attrName = state.symbols[attr.name];
        auto attrHint = [&]() -> std::string {
            return "while evaluating the '" + attrName + "' attribute passed to builtins.fetchClosure";
        };

        if (attrName == "fromPath") {
            NixStringContext context;
            fromPath = state.coerceToStorePath(attr.pos, *attr.value, context, attrHint());
        }

        else if (attrName == "toPath") {
            state.forceValue(*attr.value, attr.pos);
            bool isEmptyString = attr.value->type() == nString && attr.value->string.s == std::string("");
            if (isEmptyString) {
                toPath = StorePathOrGap {};
            }
            else {
                NixStringContext context;
                toPath = state.coerceToStorePath(attr.pos, *attr.value, context, attrHint());
            }
        }

        else if (attrName == "fromStore")
            fromStoreUrl = state.forceStringNoCtx(*attr.value, attr.pos,
                    attrHint());

        else if (attrName == "inputAddressed")
            inputAddressedMaybe = state.forceBool(*attr.value, attr.pos, attrHint());

        else
            throw Error({
                .msg = hintfmt("attribute '%s' isn't supported in call to 'fetchClosure'", attrName),
                .errPos = state.positions[pos]
            });
    }

    if (!fromPath)
        throw Error({
            .msg = hintfmt("attribute '%s' is missing in call to 'fetchClosure'", "fromPath"),
            .errPos = state.positions[pos]
        });

    bool inputAddressed = inputAddressedMaybe.value_or(false);

    if (inputAddressed) {
        if (toPath)
            throw Error({
                .msg = hintfmt("attribute '%s' is set to true, but '%s' is also set. Please remove one of them",
                    "inputAddressed",
                    "toPath"),
                .errPos = state.positions[pos]
            });
    }

    if (!fromStoreUrl)
        throw Error({
            .msg = hintfmt("attribute '%s' is missing in call to 'fetchClosure'", "fromStore"),
            .errPos = state.positions[pos]
        });

    auto parsedURL = parseURL(*fromStoreUrl);

    if (parsedURL.scheme != "http" &&
        parsedURL.scheme != "https" &&
        !(getEnv("_NIX_IN_TEST").has_value() && parsedURL.scheme == "file"))
        throw Error({
            .msg = hintfmt("'fetchClosure' only supports http:// and https:// stores"),
            .errPos = state.positions[pos]
        });

    if (!parsedURL.query.empty())
        throw Error({
            .msg = hintfmt("'fetchClosure' does not support URL query parameters (in '%s')", *fromStoreUrl),
            .errPos = state.positions[pos]
        });

    auto fromStore = openStore(parsedURL.to_string());

    if (toPath)
        runFetchClosureWithRewrite(state, pos, *fromStore, *fromPath, *toPath, v);
    else if (inputAddressed)
        runFetchClosureWithInputAddressedPath(state, pos, *fromStore, *fromPath, v);
    else
        runFetchClosureWithContentAddressedPath(state, pos, *fromStore, *fromPath, v);
}

static RegisterPrimOp primop_fetchClosure({
    .name = "__fetchClosure",
    .args = {"args"},
    .doc = R"(
      Fetch a store path [closure](@docroot@/glossary.md#gloss-closure) from a binary cache.

      This function can be used in three ways:

      - Fetch any store path and rewrite it to a fully content-addressed store path.

        Example:

        ```nix
        builtins.fetchClosure {
            fromStore = "https://cache.nixos.org";
            fromPath = /nix/store/r2jd6ygnmirm2g803mksqqjm4y39yi6i-git-2.33.1;
            toPath = /nix/store/ldbhlwhh39wha58rm61bkiiwm6j7211j-git-2.33.1;
        }
        ```

      - Fetch a content-addressed store path.

      Example:

        ```nix
        builtins.fetchClosure {
            fromStore = "https://cache.nixos.org";
            fromPath = /nix/store/ldbhlwhh39wha58rm61bkiiwm6j7211j-git-2.33.1;
        }
        ```

      - Fetch an [input-addressed store path](@docroot@/glossary.md#gloss-input-addressed-store-object) as is. This depends on user configuration, which is less preferable.

        Example:

        ```nix
        builtins.fetchClosure {
            fromStore = "https://cache.nixos.org";
            fromPath = /nix/store/r2jd6ygnmirm2g803mksqqjm4y39yi6i-git-2.33.1;
            inputAddressed = true;
        }
        ```

      **Rewriting a store path**

      This first example fetches `/nix/store/r2jd...` from the specified binary cache,
      and rewrites it into the content-addressed store path
      `/nix/store/ldbh...`.

      By rewriting the store paths, you can add the contents to any store without requiring that you or perhaps your users configure any extra trust.

      To find out the correct value for `toPath` given a `fromPath`,
      use [`nix store make-content-addressed`](@docroot@/command-ref/new-cli/nix3-store-make-content-addressed.md):

      ```console
      # nix store make-content-addressed --from https://cache.nixos.org /nix/store/r2jd6ygnmirm2g803mksqqjm4y39yi6i-git-2.33.1
      rewrote '/nix/store/r2jd6ygnmirm2g803mksqqjm4y39yi6i-git-2.33.1' to '/nix/store/ldbhlwhh39wha58rm61bkiiwm6j7211j-git-2.33.1'
      ```

      Alternatively, set `toPath = ""` and find the correct `toPath` in the error message.

      **Not rewriting**

      `toPath` may be omitted when either
       - `fromPath` is already content-addressed, or
       - `inputAddressed = true;` is set.

      Fetching an [input addressed path](@docroot@/glossary.md#gloss-input-addressed-store-object) is not recommended because it requires that the source be trusted by the Nix configuration.

      **`builtins.storePath`**

      This function is similar to [`builtins.storePath`](#builtins-storePath) in that it
      allows you to use a previously built store path in a Nix
      expression. However, it is more reproducible because it requires
      specifying a binary cache from which the path can be fetched.
      Also, using content-addressed store paths does not require users to configure [`trusted-public-keys`](@docroot@/command-ref/conf-file.md#conf-trusted-public-keys) to ensure their authenticity.
    )",
    .fun = prim_fetchClosure,
    .experimentalFeature = Xp::FetchClosure,
});

}