/*
This is a simple read-only implementation of a file system. It uses a block of data coming from the
mkespfsimg tool, and can use that block to do abstracted operations on the files that are in there.
It's written for use with httpd, but doesn't need to be used as such.
*/

#include "driver/uart.h"
#include "c_types.h"
#include "user_interface.h"
#include "espconn.h"
#include "mem.h"
#include "osapi.h"
#include "../mkespfsimage/espfsformat.h"
#include "espfs.h"

struct EspFsFile {
	EspFsHeader *header;
	char decompressor;
	int32_t posDecomp;
	char *posStart;
	char *posComp;
	void *decompData;
};

/*
Available locations, at least in my flash, with boundaries partially guessed:
0x00000 (0x10000): Code/data (RAM data?)
0x10000 (0x30000): Free (filled with zeroes) (parts used by ESPCloud and maybe SSL)
0x40000 (0x20000): Code/data (ROM data?)
0x60000 (0x1C000): Free
0x7c000 (0x04000): Param store
0x80000 - end of flash

Accessing the flash through the mem emulation at 0x40200000 is a bit hairy: All accesses
*must* be aligned 32-bit accesses. Reading a short, byte or unaligned word will result in
a memory exception, crashing the program.
*/


//Copies len bytes over from dst to src, but does it using *only*
//aligned 32-bit reads.
void ICACHE_FLASH_ATTR memcpyAligned(char *dst, char *src, int len) {
	int x;
	int w, b;
	for (x=0; x<len; x++) {
		b=((int)src&3);
		w=*((int *)(src-b));
		if (b==0) *dst=(w>>0);
		if (b==1) *dst=(w>>8);
		if (b==2) *dst=(w>>16);
		if (b==3) *dst=(w>>24);
		dst++; src++;
	}
}



EspFsFile ICACHE_FLASH_ATTR *espFsOpen(char *fileName) {
	char *p=(char *)(ESPFS_POS+0x40200000);
	char *hpos;
	char namebuf[256];
	EspFsHeader h;
	EspFsFile *r;
	//Skip initial slashes
	while(fileName[0]=='/') fileName++;
	//Go find that file!
	while(1) {
		hpos=p;
		os_memcpy(&h, p, sizeof(EspFsHeader));
		//ToDo: check magic
		if (h.flags&FLAG_LASTFILE) {
//			os_printf("End of archive.\n");
			return NULL;
		}
		p+=sizeof(EspFsHeader);
		os_memcpy(namebuf, p, sizeof(namebuf));
//		os_printf("Found file %s . Namelen=%x fileLen=%x\n", namebuf, h.nameLen,h.fileLenComp);
		if (os_strcmp(namebuf, fileName)==0) {
			p+=h.nameLen;
			r=(EspFsFile *)os_malloc(sizeof(EspFsFile));
			if (r==NULL) return NULL;
			r->header=(EspFsHeader *)hpos;
			r->decompressor=h.compression;
			r->posComp=p;
			r->posStart=p;
			r->posDecomp=0;
			r->decompData=NULL;
			//ToDo: Init any decompressor
			return r;
		}
		//Skip name and file
		p+=h.nameLen+h.fileLenComp;
		if ((int)p&3) p+=4-((int)p&3); //align to next 32bit val
//		os_printf("Next addr = %x\n", (int)p);
	}
}


int ICACHE_FLASH_ATTR espFsRead(EspFsFile *fh, char *buff, int len) {
	if (fh==NULL) return 0;
	if (fh->decompressor==COMPRESS_NONE) {
		int toRead;
		toRead=fh->header->fileLenComp-(fh->posComp-fh->posStart);
		if (len>toRead) len=toRead;
//		os_printf("Reading %d bytes from %x\n", len, fh->posComp);
		memcpyAligned(buff, fh->posComp, len);
		fh->posDecomp+=len;
		fh->posComp+=len;
//		os_printf("Done reading %d bytes, pos=%x\n", len, fh->posComp);
		return len;
	}
}

void ICACHE_FLASH_ATTR espFsClose(EspFsFile *fh) {
	if (fh==NULL) return;
	os_free(fh);
}