/*
Connector to let httpd use the espfs filesystem to serve the files in it.
*/

/*
 * ----------------------------------------------------------------------------
 * "THE BEER-WARE LICENSE" (Revision 42):
 * Jeroen Domburg <jeroen@spritesmods.com> wrote this file. As long as you retain
 * this notice you can do whatever you want with this stuff. If we meet some day,
 * and you think this stuff is worth it, you can buy me a beer in return.
 * ----------------------------------------------------------------------------
 */

#include <stddef.h>
#include <string.h>
#include "httpd.h"
#include "httpd-platform.h"
#include "cgi-espfs.h"
#include "httpd-logging.h"
#include "httpd-utils.h"
#include "espfs.h"
#include "espfsformat.h"

#define FILE_CHUNK_LEN 512

// The static files marked with FLAG_GZIP are compressed and will be served with GZIP compression.
// If the client does not advertise that he accepts GZIP send following warning message (telnet users for e.g.)
static const char *gzipNonSupportedMessage = "HTTP/1.0 501 Not implemented\r\n"
                                             "Connection: close\r\n"
                                             "Content-Type: text/plain\r\n"
                                             "Content-Length: 52\r\n"
                                             "\r\n"
                                             "Your browser does not accept gzip-compressed data.\r\n";

/**
 * Try to open a file
 * @param path - path to the file, may end with slash
 * @param indexname - filename at the path
 * @return file pointer or NULL
 */
static EspFsFile *tryOpenIndex_do(const char *path, const char *indexname)
{
    char fname[100];
    size_t url_len = strlen(path);
    strncpy(fname, path, 99);

    // Append slash if missing
    if (path[url_len - 1] != '/') {
        fname[url_len++] = '/';
    }

    strcpy(fname + url_len, indexname);

    // Try to open, returns NULL if failed
    return espFsOpen(fname);
}

/**
 * Try to find index file on a path
 * @param path - directory
 * @return file pointer or NULL
 */
EspFsFile *tryOpenIndex(const char *path)
{
    EspFsFile *file;
    // A dot in the filename probably means extension
    // no point in trying to look for index.
    if (strchr(path, '.') != NULL) { return NULL; }

    file = tryOpenIndex_do(path, "index.html");
    if (file != NULL) { return file; }

    file = tryOpenIndex_do(path, "index.htm");
    if (file != NULL) { return file; }

    file = tryOpenIndex_do(path, "index.tpl.html");
    if (file != NULL) { return file; }

    file = tryOpenIndex_do(path, "index.tpl");
    if (file != NULL) { return file; }

    return NULL; // failed to guess the right name
}

static httpd_cgi_state serveStaticFile(HttpdConnData *hconn, const char *filepath)
{
    EspFsFile *file = hconn->cgiData;
    size_t len;
    uint8_t buff[FILE_CHUNK_LEN + 1];
    char acceptEncodingBuffer[64 + 1];

    if (hconn->conn == NULL) {
        //Connection aborted. Clean up.
        espFsClose(file);
        return HTTPD_CGI_DONE;
    }

    // invalid call.
    if (filepath == NULL) {
        espfs_error("serveStaticFile called with NULL path!");
        return HTTPD_CGI_NOTFOUND;
    }

    //First call to this cgi.
    if (file == NULL) {
        //First call to this cgi. Open the file so we can read it.
        file = espFsOpen(filepath);
        if (file == NULL) {
            // file not found

            // If this is a folder, look for index file
            file = tryOpenIndex(filepath);
            if (file == NULL) { return HTTPD_CGI_NOTFOUND; }
        }

        // The gzip checking code is intentionally without #ifdefs because checking
        // for FLAG_GZIP (which indicates gzip compressed file) is very easy, doesn't
        // mean additional overhead and is actually safer to be on at all times.
        // If there are no gzipped files in the image, the code bellow will not cause any harm.

        // Check if requested file was GZIP compressed
        bool isGzip = (0 != (espFsFlags(file) & EFS_FLAG_GZIP));
        if (isGzip) {
            // Check the browser's "Accept-Encoding" header. If the client does not
            // advertise that he accepts GZIP send a warning message (telnet users for e.g.)
            httpdGetHeader(hconn, "Accept-Encoding", acceptEncodingBuffer, 64);
            if (strstr(acceptEncodingBuffer, "gzip") == NULL) {
                //No Accept-Encoding: gzip header present
                httpdSendStr(hconn, gzipNonSupportedMessage);
                espFsClose(file);
                return HTTPD_CGI_DONE;
            }
        }

        hconn->cgiData = file;
        httpdStartResponse(hconn, 200);
        const char *mime = httpdGetMimetypeOr(filepath, "application/octet-stream");
        httpdHeader(hconn, "Content-Type", mime);
        if (isGzip) {
            httpdHeader(hconn, "Content-Encoding", "gzip");
        }
        httpdAddCacheHeaders(hconn, mime);
        httpdEndHeaders(hconn);
        return HTTPD_CGI_MORE;
    }

    len = espFsRead(file, buff, FILE_CHUNK_LEN);
    if (len > 0) {
        espfs_dbg("[EspFS] Read file chunk: %d bytes", len);
        httpdSend(hconn, buff, len);
    }
    if (len != FILE_CHUNK_LEN) {
        //We're done.
        espFsClose(file);
        return HTTPD_CGI_DONE;
    } else {
        //Ok, till next time.
        return HTTPD_CGI_MORE;
    }
}


//This is a catch-all cgi function. It takes the url passed to it, looks up the corresponding
//path in the filesystem and if it exists, passes the file through. This simulates what a normal
//webserver would do with static files.
httpd_cgi_state cgiEspFsStaticFile(HttpdConnData *connData)
{
    const char *filepath = (connData->cgiArg == NULL) ? connData->url : (char *) connData->cgiArg;
    return serveStaticFile(connData, filepath);
}


//cgiEspFsTemplate can be used as a template.

typedef enum {
  ENCODE_PLAIN = 0,
  ENCODE_HTML,
  ENCODE_JS,
} TplEncode;

typedef struct {
  EspFsFile *file;

  ssize_t tokenPos;
  char buff[FILE_CHUNK_LEN + 1];
  char token[HTTPD_ESPFS_TOKEN_LEN];
  char *pToken;

  bool chunk_resume;
  size_t buff_len;
  size_t buff_x;
  size_t buff_sp;
  char *buff_e;
  TplEncode tokEncode;
} TplDataInternal;


int tplSendN(HttpdConnData *conn, const char *str, size_t len)
{
    if (conn == NULL) { return 0; }

    TplDataInternal *tdi = conn->cgiData;
    if (!tdi) { return 0; }

    if (tdi->tokEncode == ENCODE_PLAIN) {
        return httpdSendStrN(conn, str, len);
    } else if (tdi->tokEncode == ENCODE_HTML) {
        return httpdSend_html(conn, str, (ssize_t) len);
    } else if (tdi->tokEncode == ENCODE_JS) {
        return httpdSend_js(conn, str, (ssize_t) len);
    }
    return 0;
}


httpd_cgi_state cgiEspFsTemplate(HttpdConnData *conn)
{
    TplDataInternal *tdi = conn->cgiData;

    size_t len, x, sp;
    char *e = NULL;

    if (conn->conn == NULL) {
        //Connection aborted. Clean up.
        if (tdi) {
            TplCallback callback = (TplCallback) conn->cgiArg;
            if (callback) {
                callback(conn, NULL);
            }

            espFsClose(tdi->file);
            httpdPlatFree(tdi);
        }
        return HTTPD_CGI_DONE;
    }

    if (tdi == NULL) {
        //First call to this cgi. Open the file so we can read it.
        tdi = (TplDataInternal *) httpdPlatMalloc(sizeof(TplDataInternal));
        if (tdi == NULL) {
            espfs_error("Failed to malloc tpl struct");
            return HTTPD_CGI_NOTFOUND;
        }

        tdi->chunk_resume = false;

        const char *filepath = conn->url;
        // check for custom template URL
        if (conn->cgiArg2 != NULL) {
            filepath = conn->cgiArg2;
            espfs_dbg("Using filepath %s", filepath);
        }

        tdi->file = espFsOpen(filepath);

        if (tdi->file == NULL) {
            // maybe a folder, look for index file
            tdi->file = tryOpenIndex(filepath);
            if (tdi->file == NULL) {
                espfs_error("cgiEspFsTemplate: Couldn't find template for path: %s", conn->url);
                httpdPlatFree(tdi);
                return HTTPD_CGI_NOTFOUND;
            }
        }

        if (espFsFlags(tdi->file) & EFS_FLAG_GZIP) {
            espfs_error("cgiEspFsTemplate: Trying to use gzip-compressed file %s as template!", conn->url);
            espFsClose(tdi->file);
            httpdPlatFree(tdi);
            return HTTPD_CGI_NOTFOUND;
        }

        tdi->tokenPos = -1;
        conn->cgiData = tdi;
        httpdStartResponse(conn, 200);
        // Try to extension from the URL
        const char *mime = httpdGetMimetype(conn->url);
        if (!mime) {
            // Get extension from the template file
            mime = httpdGetMimetype(filepath);
        }
        if (!mime) {
            // Still unresolved...
            mime = "text/html"; // this is generally a good fallback for templates
        }

        httpdHeader(conn, "Content-Type", mime);
        httpdAddCacheHeaders(conn, mime);
        httpdEndHeaders(conn);
        return HTTPD_CGI_MORE;
    }

    char *buff = tdi->buff;

    // resume the parser state from the last token,
    // if subst. func wants more data to be sent.
    if (tdi->chunk_resume) {
        //espfs_dbg("Resuming tpl parser for multi-part subst");
        len = tdi->buff_len;
        e = tdi->buff_e;
        sp = tdi->buff_sp;
        x = tdi->buff_x;
    } else {
        len = espFsRead(tdi->file, (uint8_t *) buff, FILE_CHUNK_LEN);
        tdi->buff_len = len;

        e = buff;
        sp = 0;
        x = 0;
    }

    if (len > 0) {
        for (; x < len; x++) {
            char c = buff[x];

            if (tdi->tokenPos == -1) {
                //Inside ordinary text.
                if (c == '%') {
                    //Send raw data up to now
                    if (sp != 0) { httpdSendStrN(conn, e, sp); }
                    sp = 0;
                    //Go collect token chars.
                    tdi->tokenPos = 0;
                } else {
                    sp++;
                }
            } else {
                if (c == '%') {
                    if (tdi->tokenPos == 0) {
                        //This is the second % of a %% escape string.
                        //Send a single % and resume with the normal program flow.
                        httpdSendStrN(conn, "%", 1);
                    } else {
                        if (!tdi->chunk_resume) {
                            //This is an actual token.
                            tdi->token[tdi->tokenPos++] = 0; //zero-terminate token

                            int prefixLen = 0;
                            tdi->tokEncode = ENCODE_PLAIN;
                            if (strneq(tdi->token, "html:", 5)) {
                                prefixLen = 5;
                                tdi->tokEncode = ENCODE_HTML;
                            } else if (strneq(tdi->token, "h:", 2)) {
                                prefixLen = 2;
                                tdi->tokEncode = ENCODE_HTML;
                            } else if (strneq(tdi->token, "js:", 3)) {
                                prefixLen = 3;
                                tdi->tokEncode = ENCODE_JS;
                            } else if (strneq(tdi->token, "j:", 2)) {
                                prefixLen = 2;
                                tdi->tokEncode = ENCODE_JS;
                            }

                            tdi->pToken = &tdi->token[prefixLen];
                        }

                        tdi->chunk_resume = false;

                        TplCallback callback = (TplCallback) conn->cgiArg;
                        httpd_cgi_state status = callback(conn, tdi->pToken);
                        if (status == HTTPD_CGI_MORE) {
//							espfs_dbg("Multi-part tpl subst, saving parser state");
                            // wants to send more in this token's place.....
                            tdi->chunk_resume = true;
                            tdi->buff_len = len;
                            tdi->buff_e = e;
                            tdi->buff_sp = sp;
                            tdi->buff_x = x;
                            break;
                        }
                        else if (status == HTTPD_CGI_NOTFOUND) {
                            tdi->tokenPos--; // undo the ++ above
                            goto put_token_back;
                        }
                    }
                    //Go collect normal chars again.
                    e = &buff[x + 1];
                    tdi->tokenPos = -1;
                } else {
                    // Add char to the token buf
                    bool outOfSpace = tdi->tokenPos >= ((int) sizeof(tdi->token) - 1);
                    if (outOfSpace) {
                    put_token_back:
                        // looks like we collected some garbage, put it back
                        httpdSendStrN(conn, "%", 1);
                        if (tdi->tokenPos > 0) {
                            httpdSendStrN(conn, tdi->token, (size_t) tdi->tokenPos);
                        }
                        // the bad char
                        httpdSendStrN(conn, &c, 1);

                        //Go collect normal chars again.
                        e = &buff[x + 1];
                        tdi->tokenPos = -1;
                    } else {
                        // collect it
                        tdi->token[tdi->tokenPos++] = c;
                    }
                }
            }
        }
    }

    if (tdi->chunk_resume) {
        return HTTPD_CGI_MORE;
    }

    //Send remaining bit.
    if (sp != 0) {
        httpdSendStrN(conn, e, (size_t) sp);
    }

    if (len != FILE_CHUNK_LEN) {
        //We're done.

        TplCallback callback = (TplCallback) conn->cgiArg;
        if (callback) {
            callback(conn, NULL);
        }

        espfs_info("Template sent.");
        espFsClose(tdi->file);
        httpdPlatFree(tdi);
        return HTTPD_CGI_DONE;
    } else {
        //Ok, till next time.
        return HTTPD_CGI_MORE;
    }
}