#include "http.hpp"
#include "wrap-sstream.hpp"
#include "wrap-string.hpp"
#include "luastack.hpp"
#include <cstdint>

static void url_encode(const eng::string &value, StreamBuffer *sb) {
    const char *hexdigits = "0123456789ABCDEF";
    for (int i = 0; i < int(value.size()); i++) {
        char c = value[i];

        if (util::ascii_isalnum(c) || c == '-' || c == '_' || c == '.' || c == '~' || (c == '/')) {
            sb->write_char(c);
        } else if (c == ' ') {
            sb->write_char('+');
        } else {
            sb->write_char('%');
            sb->write_char(hexdigits[c>>4]);
            sb->write_char(hexdigits[c&15]);
        }
    }
}

class ErrorStringStream : public eng::ostringstream {
private:
    eng::string *target_;
public:
    ErrorStringStream(eng::string *target) : target_(target) {}
    ~ErrorStringStream() {
        if (target_->empty()) {
            (*target_) = str();
        }
    }
};

HttpRequest::HttpRequest() {
    verify_certificate_ = true;
    port_ = 0;
}

void HttpRequest::set_verify_certificate(bool flag) {
    verify_certificate_ = flag;
}

eng::string HttpRequest::target() const {
    assert(check().empty());
    eng::ostringstream oss;
    oss << (verify_certificate_ ? "cert" : "nocert");
    oss << ':' << host_ << ':' << port_;
    return oss.str();
}

void HttpRequest::set_method(const eng::string &s) {
    eng::string method = util::ascii_toupper(s);
    if ((method != "GET") && (method != "HEAD")) {
        ErrorStringStream error(&error_);
        error << "HTTPS method not implemented: " << method;
        error << ". Currently, only HEAD and GET are implemented.";
        return;
    }
    if ((!method_.empty()) && (method_ != method)) {
        ErrorStringStream error(&error_);
        error << "HTTPS method specified twice: " << method_ << " and " << method;
        return;
    }
    method_ = method;
}

void HttpRequest::set_host(const eng::string &s) {
    eng::string host = util::ascii_tolower(s);
    if (host.empty()) {
        ErrorStringStream error(&error_);
        error << "HTTPS hostname cannot be empty string.";
        return;
    }
    // This is not quite strict, but it's close.  I believe
    // the DNS lookup will fail for invalid hostnames anyway.
    for (char c : host) {
        if ((c != '-') && (c != '.') && (!util::ascii_isalnum(c))) {
            ErrorStringStream error(&error_);
            error << "HTTPS hostnames can only contain letters, digits, and hyphen: " << host;
            return;
        }
    }
    if (!host_.empty()) {
        ErrorStringStream error(&error_);
        error << "HTTPS hostname specified twice: " << host_ << " and " << host;
        return;
    }
    host_ = host;
}

void HttpRequest::set_port(int port) {
    if ((port < 1) || (port > 65535)) {
        ErrorStringStream error(&error_);
        error << "HTTP port must be between 1 and 65535: " << port;
        return;
    }
    if (port_ != 0) {
        ErrorStringStream error(&error_);
        error << "HTTPS port specified twice: " << port_ << " and " << port;
        return;
    }
    port_ = port;
}

void HttpRequest::set_url(const eng::string &url) {
    if (util::has_prefix(url, "https://")) {
        ErrorStringStream error(&error_);
        error << "set_url(full_url) not implemented yet.";
        return;
    } else if (util::has_prefix(url, "/")) {
        if (!path_.empty()) {
            ErrorStringStream error(&error_);
            error << "HTTP path specified twice: " << path_ << " and " << url;
            return;
        }
        path_ = url;
    } else {
        ErrorStringStream error(&error_);
        error << "HTTP url must start with https://, or with /";
        return;
    }
}

void HttpRequest::set_param(const eng::string &key, const eng::string &val) {
    if (params_.find(key) != params_.end()) {
        ErrorStringStream error(&error_);
        error << "HTTP url parameter specified twice: " << key;
        return;
    }
    params_[key] = val;
}

void HttpRequest::set_verify_certificate(LuaStack &LS, LuaSlot val) {
    if (!LS.isboolean(val)) {
        ErrorStringStream error(&error_);
        error << "HTTP verify_certificate must be a boolean";
        return;
    }
    set_verify_certificate(LS.ckboolean(val));
}

void HttpRequest::set_method(LuaStack &LS, LuaSlot val) {
    if (!LS.isstring(val)) {
        ErrorStringStream error(&error_);
        error << "HTTP method must be a string";
        return;
    }
    set_method(LS.ckstring(val));
}

void HttpRequest::set_host(LuaStack &LS, LuaSlot val) {
    if (!LS.isstring(val)) {
        ErrorStringStream error(&error_);
        error << "HTTP host must be a string";
        return;
    }
    set_host(LS.ckstring(val));
}

void HttpRequest::set_port(LuaStack &LS, LuaSlot val) {
    if (!LS.isint(val)) {
        ErrorStringStream error(&error_);
        error << "HTTP port must be an int";
        return;
    }
    set_port(LS.ckint(val));
}

void HttpRequest::set_url(LuaStack &LS, LuaSlot val) {
    if (!LS.isstring(val)) {
        ErrorStringStream error(&error_);
        error << "HTTP url must be a string";
        return;
    }
    set_url(LS.ckstring(val));
}

void HttpRequest::set_param(LuaStack &LS, LuaSlot key, LuaSlot val) {
    if (!LS.isstring(key)) {
        ErrorStringStream error(&error_);
        error << "HTTP url parameter key must be a string";
        return;
    }
    if (!LS.isstring(val)) {
        ErrorStringStream error(&error_);
        error << "HTTP url parameter val must be a string";
        return;
    }
    set_param(LS.ckstring(key), LS.ckstring(val));
}

void HttpRequest::set_params(LuaStack &LS0, LuaSlot tab) {
    if (!LS0.istable(tab)) {
        ErrorStringStream error(&error_);
        error << "HTTP params must be a table";
        return;
    }
    LuaVar key, val;
    LuaStack LS(LS0.state(), key, val);
    LS.set(key, LuaNil);
    while (LS.next(tab, key, val)) {
        set_param(LS, key, val);
    }
}

void HttpRequest::set_defaults() {
    if (method_.empty()) {
        method_ = "GET";
    }
    if (port_ == 0) {
        port_ = 443;
    }
}

void HttpRequest::set_config(LuaStack &LS0, LuaSlot tab) {
    LuaVar key, val;
    LuaStack LS(LS0.state(), key, val);
    LS.set(key, LuaNil);
    while (LS.next(tab, key, val)) {
        eng::string kstr;
        if (LS.isstring(key)) kstr = LS.ckstring(key);
        if (kstr == "method") {
            set_method(LS, val);
        } else if (kstr == "host") {
            set_host(LS, val);
        } else if (kstr == "port") {
            set_port(LS, val);
        } else if (kstr == "url") {
            set_url(LS, val);
        } else if (kstr == "params") {
            set_params(LS, val);
        } else if (kstr == "verifycertificate") {
            set_verify_certificate(LS, val);
        } else if (kstr == "") {
            ErrorStringStream error(&error_);
            error << "HTTP config parameter names must be strings.";
        } else {
            ErrorStringStream error(&error_);
            error << "HTTP unrecognized config parameter: " << kstr;
        }
    }
}

eng::string HttpRequest::check() const {
    if (!error_.empty()) {
        return error_;
    }
    if (method_.empty()) {
        return "HTTP method has not been set";
    }
    if (host_.empty()) {
        return "HTTP host has not been set";
    }
    if (port_ == 0) {
        return "HTTP port has not been set";
    }
    if (path_.empty()) {
        return "HTTP url has not been set";
    }
    return "";
}

void HttpRequest::send_internal(StreamBuffer *sb, bool debug_string) const {
    // If there's an error in the request, handle it.  In debug string mode,
    // we just put the error into the output.  In production mode, we assert
    // fail.
    eng::string error = check();
    if (debug_string) {
        if (!error.empty()) {
            sb->write_bytes(error);
            return;
        }
    } else {
        assert(error.empty());
    }

    // Choose a linebreak.
    eng::string linebreak = (debug_string) ? "\n" : "\r\n";

    // Send the command.
    sb->write_bytes(method_);
    sb->write_char(' ');
    url_encode(path_, sb);
    bool first_param = true;
    for (const auto &pair : params_) {
        sb->write_char(first_param ? '?' : '&');
        url_encode(pair.first, sb);
        sb->write_char('=');
        url_encode(pair.second, sb);
        first_param = false;
    }
    sb->write_bytes(" HTTP/1.1");
    sb->write_bytes(linebreak);

    // Send the host header.
    sb->write_bytes("Host: ");
    sb->write_bytes(host_);
    sb->write_char(':');
    sb->ostream() << port_;
    sb->write_bytes(linebreak);

    // The empty accept-encoding header notifies the
    // server that we don't support gzip, deflate, or
    // other content compression.
    sb->write_bytes("Accept-encoding:");
    sb->write_bytes(linebreak);

    // Add a user-agent header.  Not sure why.
    sb->write_bytes("User-agent: Mozilla 5.0 (luprex)");
    sb->write_bytes(linebreak);

    // Send the extra linebreak.
    if (!debug_string) {
        sb->write_bytes(linebreak);
    }
}

eng::string HttpRequest::DebugString() {
    StreamBuffer sb;
    send_internal(&sb, true);
    return eng::string(sb.view());
}

HttpResponse::HttpResponse() {
    response_code_ = 0;
    response_length_ = 0;
    mime_type_ = "application/empty";
}

void HttpResponse::fail(int response_code, const eng::string &error) {
    response_code_ = response_code;
    error_ = error;
    response_length_ = 0;
    mime_type_ = "application/empty";
    content_ = "";
}

static std::string_view readline(std::string_view &v) {
    std::string_view result = util::sv_split_one(v, '\n');
    return util::sv_rtrim(result, '\r');    
}

void HttpResponse::parse(const StreamBuffer *sb) {
    // We're not going to modify the StreamBuffer at all.
    // Instead, we work entirely on a view.
    std::string_view view = sb->view();

    // Special case this.
    if (view.empty()) {
        fail(500, "HTTP server response completely empty");
        return;
    }

    // Parse the status line.
    std::string_view status = readline(view);
    if (status.empty()) {
        fail(500, "HTTP status-line not present in response");
        return;
    }
    //std::string_view status_code = util::sv_split_one(status, ' ');
    



}

LuaDefine(http_request, "reqtab",
    "|Given an HTTP request in the form of a table, returns the same "
    "|request as a string, to assist with debugging."
    "|"
    "|The table can contain:"
    "|"
    "|  method             (ie, GET, HEAD, POST, etc)"
    "|  host               (ie, 'google.com')"
    "|  port               (default: 443)"
    "|  url                (ie, '/index.html')"
    "|  params             (a table of url parameters)"
    "|  verifycertificate  (default: true)"
    "|"
    "|The url can start with 'https://', or with '/'.  If it starts"
    "|with 'https://', then the URL includes the host and port, which"
    "|then must not be specified separately."
    "|"
    "|Note that plain HTTP is not supported - we only allow HTTPS."
    "|However, you can talk to a server that has a dummy certificate"
    "|by specifying verifycertificate=false."
    "|"
    "|This module will automatically url encode everything for you."
    "|Therefore, you shouldn't url encode anything, otherwise,"
    "|you'll end up double-encoding."
    "|"
    "|You cannot include url parameters as part of the url.  If you try,"
    "|then your ?, &, and = characters will get url encoded, which will"
    "|cause them to not function.  To use url parameters, you must"
    "|use the separate params table."
    "|") {
    LuaArg tab;
    LuaRet str;
    LuaStack LS(L, tab, str);
    HttpRequest req;
    req.set_config(LS, tab);
    req.set_defaults();
    eng::string error = req.check();
    if (!error.empty()) {
        luaL_error(L, "%s", error.c_str());
        return 0;
    }
    LS.set(str, req.DebugString());
    return LS.result();
}