#include "fetchers.hh"
#include "download.hh"
#include "globals.hh"
#include "parse.hh"
#include "regex.hh"
#include "store-api.hh"

#include <nlohmann/json.hpp>

namespace nix::fetchers {

std::regex ownerRegex("[a-zA-Z][a-zA-Z0-9_-]*", std::regex::ECMAScript);
std::regex repoRegex("[a-zA-Z][a-zA-Z0-9_-]*", std::regex::ECMAScript);

struct GitHubInput : Input
{
    std::string owner;
    std::string repo;
    std::optional<std::string> ref;
    std::optional<Hash> rev;

    bool operator ==(const Input & other) const override
    {
        auto other2 = dynamic_cast<const GitHubInput *>(&other);
        return
            other2
            && owner == other2->owner
            && repo == other2->repo
            && rev == other2->rev
            && ref == other2->ref;
    }

    bool isImmutable() const override
    {
        return (bool) rev;
    }

    std::optional<std::string> getRef() const override { return ref; }

    std::optional<Hash> getRev() const override { return rev; }

    std::string to_string() const override
    {
        auto s = fmt("github:%s/%s", owner, repo);
        assert(!(ref && rev));
        if (ref) s += "/" + *ref;
        if (rev) s += "/" + rev->to_string(Base16, false);
        return s;
    }

    void clone(const Path & destDir) const override
    {
        std::shared_ptr<const Input> input = inputFromURL(fmt("git+ssh://git@github.com/%s/%s.git", owner, repo));
        input = input->applyOverrides(ref.value_or("master"), rev);
        input->clone(destDir);
    }

    std::pair<Tree, std::shared_ptr<const Input>> fetchTreeInternal(nix::ref<Store> store) const override
    {
        auto rev = this->rev;

    #if 0
        if (rev) {
            if (auto gitInfo = lookupGitInfo(store, "source", *rev))
                return *gitInfo;
        }
    #endif

        if (!rev) {
            auto url = fmt("https://api.github.com/repos/%s/%s/commits/%s",
                owner, repo, ref ? *ref : "master");
            CachedDownloadRequest request(url);
            request.ttl = rev ? 1000000000 : settings.tarballTtl;
            auto result = getDownloader()->downloadCached(store, request);
            auto json = nlohmann::json::parse(readFile(result.path));
            rev = Hash(json["sha"], htSHA1);
            debug("HEAD revision for '%s' is %s", url, rev->gitRev());
        }

        // FIXME: use regular /archive URLs instead? api.github.com
        // might have stricter rate limits.

        auto url = fmt("https://api.github.com/repos/%s/%s/tarball/%s",
            owner, repo, rev->to_string(Base16, false));

        std::string accessToken = settings.githubAccessToken.get();
        if (accessToken != "")
            url += "?access_token=" + accessToken;

        CachedDownloadRequest request(url);
        request.unpack = true;
        request.name = "source";
        request.ttl = 1000000000;
        request.getLastModified = true;
        auto dresult = getDownloader()->downloadCached(store, request);

        assert(dresult.lastModified);

        Tree result{
            .actualPath = dresult.path,
            .storePath = store->parseStorePath(dresult.storePath),
            .rev = *rev,
            .lastModified = *dresult.lastModified
        };

    #if 0
        // FIXME: this can overwrite a cache file that contains a revCount.
        cacheGitInfo("source", gitInfo);
    #endif

        auto input = std::make_shared<GitHubInput>(*this);
        input->ref = {};
        input->rev = *rev;

        return {std::move(result), input};
    }

    std::shared_ptr<const Input> applyOverrides(
        std::optional<std::string> ref,
        std::optional<Hash> rev) const override
    {
        if (!ref && !rev) return shared_from_this();

        auto res = std::make_shared<GitHubInput>(*this);

        if (ref) res->ref = ref;
        if (rev) res->rev = rev;

        return res;
    }
};

struct GitHubInputScheme : InputScheme
{
    std::unique_ptr<Input> inputFromURL(const ParsedURL & url) override
    {
        if (url.scheme != "github") return nullptr;

        auto path = tokenizeString<std::vector<std::string>>(url.path, "/");
        auto input = std::make_unique<GitHubInput>();
        input->type = "github";

        if (path.size() == 2) {
        } else if (path.size() == 3) {
            if (std::regex_match(path[2], revRegex))
                input->rev = Hash(path[2], htSHA1);
            else if (std::regex_match(path[2], refRegex))
                input->ref = path[2];
            else
                throw BadURL("in GitHub URL '%s', '%s' is not a commit hash or branch/tag name", url.url, path[2]);
        } else
            throw BadURL("GitHub URL '%s' is invalid", url.url);

        for (auto &[name, value] : url.query) {
            if (name == "rev") {
                if (!std::regex_match(value, revRegex))
                    throw BadURL("GitHub URL '%s' contains an invalid commit hash", url.url);
                if (input->rev)
                    throw BadURL("GitHub URL '%s' contains multiple commit hashes", url.url);
                input->rev = Hash(value, htSHA1);
            }
            else if (name == "ref") {
                if (!std::regex_match(value, refRegex))
                    throw BadURL("GitHub URL '%s' contains an invalid branch/tag name", url.url);
                if (input->ref)
                    throw BadURL("GitHub URL '%s' contains multiple branch/tag names", url.url);
                input->ref = value;
            }
        }

        if (input->ref && input->rev)
            throw BadURL("GitHub URL '%s' contains both a commit hash and a branch/tag name", url.url);

        input->owner = path[0];
        input->repo = path[1];

        return input;
    }
};

static auto r1 = OnStartup([] { registerInputScheme(std::make_unique<GitHubInputScheme>()); });

}