/* Adapted from toybox's patch. */

/* vi: set sw=4 ts=4:
 *
 * patch.c - Apply a "universal" diff.
 *
 * Copyright 2007 Rob Landley <rob@landley.net>
 *
 * see http://www.opengroup.org/onlinepubs/009695399/utilities/patch.html
 * (But only does -u, because who still cares about "ed"?)
 *
 * TODO:
 * -b backup
 * -l treat all whitespace as a single space
 * -N ignore already applied
 * -d chdir first
 * -D define wrap #ifdef and #ifndef around changes
 * -o outfile output here instead of in place
 * -r rejectfile write rejected hunks to this file
 *
 * -E remove empty files --remove-empty-files
 * -f force (no questions asked)
 * -F fuzz (number, default 2)
 * [file] which file to patch

USE_PATCH(NEWTOY(patch, USE_TOYBOX_DEBUG("x")"up#i:R", TOYFLAG_USR|TOYFLAG_BIN))

config PATCH
        bool "patch (9.4 kb)"
        default y
        help
          usage: patch [-i file] [-p depth] [-Ru]

          Apply a unified diff to one or more files.

          -i    Input file (defaults=stdin)
          -p    number of '/' to strip from start of file paths (default=all)
          -R    Reverse patch.
          -u    Ignored (only handles "unified" diffs)

          This version of patch only handles unified diffs, and only modifies
          a file when all all hunks to that file apply.  Patch prints failed
          hunks to stderr, and exits with nonzero status if any hunks fail.

          A file compared against /dev/null (or with a date <= the epoch) is
          created/deleted as appropriate.
*/
#include "libbb.h"

struct double_list {
        struct double_list *next;
        struct double_list *prev;
        char *data;
};

// Return the first item from the list, advancing the list (which must be called
// as &list)
static
void *TOY_llist_pop(void *list)
{
        // I'd use a void ** for the argument, and even accept the typecast in all
        // callers as documentation you need the &, except the stupid compiler
        // would then scream about type-punned pointers.  Screw it.
        void **llist = (void **)list;
        void **next = (void **)*llist;
        *llist = *next;

        return (void *)next;
}

// Free all the elements of a linked list
// if freeit!=NULL call freeit() on each element before freeing it.
static
void TOY_llist_free(void *list, void (*freeit)(void *data))
{
        while (list) {
                void *pop = TOY_llist_pop(&list);
                if (freeit) freeit(pop);
                else free(pop);

                // End doubly linked list too.
                if (list==pop) break;
        }
}

// Add an entry to the end off a doubly linked list
static
struct double_list *dlist_add(struct double_list **list, char *data)
{
        struct double_list *line = xmalloc(sizeof(struct double_list));

        line->data = data;
        if (*list) {
                line->next = *list;
                line->prev = (*list)->prev;
                (*list)->prev->next = line;
                (*list)->prev = line;
        } else *list = line->next = line->prev = line;

        return line;
}

// Ensure entire path exists.
// If mode != -1 set permissions on newly created dirs.
// Requires that path string be writable (for temporary null terminators).
static
void xmkpath(char *path, int mode)
{
        char *p, old;
        mode_t mask;
        int rc;
        struct stat st;

        for (p = path; ; p++) {
                if (!*p || *p == '/') {
                        old = *p;
                        *p = rc = 0;
                        if (stat(path, &st) || !S_ISDIR(st.st_mode)) {
                                if (mode != -1) {
                                        mask = umask(0);
                                        rc = mkdir(path, mode);
                                        umask(mask);
                                } else rc = mkdir(path, 0777);
                        }
                        *p = old;
                        if(rc) bb_perror_msg_and_die("mkpath '%s'", path);
                }
                if (!*p) break;
        }
}

// Slow, but small.
static
char *get_rawline(int fd, long *plen, char end)
{
        char c, *buf = NULL;
        long len = 0;

        for (;;) {
                if (1>read(fd, &c, 1)) break;
                if (!(len & 63)) buf=xrealloc(buf, len+65);
                if ((buf[len++]=c) == end) break;
        }
        if (buf) buf[len]=0;
        if (plen) *plen = len;

        return buf;
}

static
char *get_line(int fd)
{
        long len;
        char *buf = get_rawline(fd, &len, '\n');

        if (buf && buf[--len]=='\n') buf[len]=0;

        return buf;
}

// Copy the rest of in to out and close both files.
static
void xsendfile(int in, int out)
{
        long len;
        char buf[4096];

        if (in<0) return;
        for (;;) {
                len = safe_read(in, buf, 4096);
                if (len<1) break;
                xwrite(out, buf, len);
        }
}

// Copy the rest of the data and replace the original with the copy.
static
void replace_tempfile(int fdin, int fdout, char **tempname)
{
        char *temp = xstrdup(*tempname);

        temp[strlen(temp)-6]=0;
        if (fdin != -1) {
                xsendfile(fdin, fdout);
                xclose(fdin);
        }
        xclose(fdout);
        rename(*tempname, temp);
        free(*tempname);
        free(temp);
        *tempname = NULL;
}

// Open a temporary file to copy an existing file into.
static
int copy_tempfile(int fdin, char *name, char **tempname)
{
        struct stat statbuf;
        int fd;

        *tempname = xasprintf("%sXXXXXX", name);
        fd = mkstemp(*tempname);
        if(-1 == fd) bb_simple_perror_msg_and_die("no temp file");

        // Set permissions of output file
        fstat(fdin, &statbuf);
        fchmod(fd, statbuf.st_mode);

        return fd;
}

// Abort the copy and delete the temporary file.
static
void delete_tempfile(int fdin, int fdout, char **tempname)
{
        close(fdin);
        close(fdout);
        unlink(*tempname);
        free(*tempname);
        *tempname = NULL;
}



struct globals {
        char *infile;
        long prefix;

        struct double_list *current_hunk;
        long oldline, oldlen, newline, newlen, linenum;
        int context, state, filein, fileout, filepatch, hunknum;
        char *tempname;

        // was toys.foo:
        int exitval;
};
#define TT (*ptr_to_globals)
#define INIT_TT() do { \
        SET_PTR_TO_GLOBALS(xzalloc(sizeof(TT))); \
} while (0)


//bbox had: "p:i:RN"
#define FLAG_STR "Rup:i:x"
/* FLAG_REVERSE must be == 1! Code uses this fact. */
#define FLAG_REVERSE (1 << 0)
#define FLAG_u       (1 << 1)
#define FLAG_PATHLEN (1 << 2)
#define FLAG_INPUT   (1 << 3)
//non-standard:
#define FLAG_DEBUG   (1 << 4)

// Dispose of a line of input, either by writing it out or discarding it.

// state < 2: just free
// state = 2: write whole line to stderr
// state = 3: write whole line to fileout
// state > 3: write line+1 to fileout when *line != state

#define PATCH_DEBUG (option_mask32 & FLAG_DEBUG)

static void do_line(void *data)
{
        struct double_list *dlist = (struct double_list *)data;

        if (TT.state>1 && *dlist->data != TT.state)
                fdprintf(TT.state == 2 ? 2 : TT.fileout,
                        "%s\n", dlist->data+(TT.state>3 ? 1 : 0));

        if (PATCH_DEBUG) fdprintf(2, "DO %d: %s\n", TT.state, dlist->data);

        free(dlist->data);
        free(data);
}

static void finish_oldfile(void)
{
        if (TT.tempname) replace_tempfile(TT.filein, TT.fileout, &TT.tempname);
        TT.fileout = TT.filein = -1;
}

static void fail_hunk(void)
{
        if (!TT.current_hunk) return;
        TT.current_hunk->prev->next = 0;

        fdprintf(2, "Hunk %d FAILED %ld/%ld.\n", TT.hunknum, TT.oldline, TT.newline);
        TT.exitval = 1;

        // If we got to this point, we've seeked to the end.  Discard changes to
        // this file and advance to next file.

        TT.state = 2;
        TOY_llist_free(TT.current_hunk, do_line);
        TT.current_hunk = NULL;
        delete_tempfile(TT.filein, TT.fileout, &TT.tempname);
        TT.state = 0;
}

// Given a hunk of a unified diff, make the appropriate change to the file.
// This does not use the location information, but instead treats a hunk
// as a sort of regex.  Copies data from input to output until it finds
// the change to be made, then outputs the changed data and returns.
// (Finding EOF first is an error.)  This is a single pass operation, so
// multiple hunks must occur in order in the file.

static int apply_one_hunk(void)
{
        struct double_list *plist, *buf = NULL, *check;
        int matcheof = 0, reverse = option_mask32 & FLAG_REVERSE, backwarn = 0;

        // Break doubly linked list so we can use singly linked traversal function.
        TT.current_hunk->prev->next = NULL;

        // Match EOF if there aren't as many ending context lines as beginning
        for (plist = TT.current_hunk; plist; plist = plist->next) {
                if (plist->data[0]==' ') matcheof++;
                else matcheof = 0;
                if (PATCH_DEBUG) fdprintf(2, "HUNK:%s\n", plist->data);
        }
        matcheof = matcheof < TT.context;

        if (PATCH_DEBUG) fdprintf(2,"MATCHEOF=%c\n", matcheof ? 'Y' : 'N');

        // Loop through input data searching for this hunk.  Match all context
        // lines and all lines to be removed until we've found the end of a
        // complete hunk.
        plist = TT.current_hunk;
        buf = NULL;
        if (TT.context) for (;;) {
                char *data = get_line(TT.filein);

                TT.linenum++;

                // Figure out which line of hunk to compare with next.  (Skip lines
                // of the hunk we'd be adding.)
                while (plist && *plist->data == "+-"[reverse]) {
                        if (data && strcmp(data, plist->data+1) == 0) {
                                if (!backwarn) {
                                        fdprintf(2,"Possibly reversed hunk %d at %ld\n",
                                                TT.hunknum, TT.linenum);
                                        backwarn++;
                                }
                        }
                        plist = plist->next;
                }

                // Is this EOF?
                if (!data) {
                        if (PATCH_DEBUG) fdprintf(2, "INEOF\n");

                        // Does this hunk need to match EOF?
                        if (!plist && matcheof) break;

                        // File ended before we found a place for this hunk.
                        fail_hunk();
                        goto done;
                } else if (PATCH_DEBUG) fdprintf(2, "IN: %s\n", data);
                check = dlist_add(&buf, data);

                // Compare this line with next expected line of hunk.
                // todo: teach the strcmp() to ignore whitespace.

                // A match can fail because the next line doesn't match, or because
                // we hit the end of a hunk that needed EOF, and this isn't EOF.

                // If match failed, flush first line of buffered data and
                // recheck buffered data for a new match until we find one or run
                // out of buffer.

                for (;;) {
                        if (!plist || strcmp(check->data, plist->data+1)) {
                                // Match failed.  Write out first line of buffered data and
                                // recheck remaining buffered data for a new match.

                                if (PATCH_DEBUG)
                                        fdprintf(2, "NOT: %s\n", plist->data);

                                TT.state = 3;
                                check = TOY_llist_pop(&buf);
                                check->prev->next = buf;
                                buf->prev = check->prev;
                                do_line(check);
                                plist = TT.current_hunk;

                                // If we've reached the end of the buffer without confirming a
                                // match, read more lines.
                                if (check==buf) {
                                        buf = 0;
                                        break;
                                }
                                check = buf;
                        } else {
                                if (PATCH_DEBUG)
                                        fdprintf(2, "MAYBE: %s\n", plist->data);
                                // This line matches.  Advance plist, detect successful match.
                                plist = plist->next;
                                if (!plist && !matcheof) goto out;
                                check = check->next;
                                if (check == buf) break;
                        }
                }
        }
out:
        // We have a match.  Emit changed data.
        TT.state = "-+"[reverse];
        TOY_llist_free(TT.current_hunk, do_line);
        TT.current_hunk = NULL;
        TT.state = 1;
done:
        if (buf) {
                buf->prev->next = NULL;
                TOY_llist_free(buf, do_line);
        }

        return TT.state;
}

// Read a patch file and find hunks, opening/creating/deleting files.
// Call apply_one_hunk() on each hunk.

// state 0: Not in a hunk, look for +++.
// state 1: Found +++ file indicator, look for @@
// state 2: In hunk: counting initial context lines
// state 3: In hunk: getting body

int patch_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int patch_main(int argc UNUSED_PARAM, char **argv)
{
        int opts;
        int reverse, state = 0;
        char *oldname = NULL, *newname = NULL;
        char *opt_p, *opt_i;

        INIT_TT();

        opts = getopt32(argv, FLAG_STR, &opt_p, &opt_i);
        reverse = opts & FLAG_REVERSE;
        TT.prefix = (opts & FLAG_PATHLEN) ? xatoi(opt_p) : 0; // can be negative!
        if (opts & FLAG_INPUT) TT.filepatch = xopen(opt_i, O_RDONLY);
        TT.filein = TT.fileout = -1;

        // Loop through the lines in the patch
        for(;;) {
                char *patchline;

                patchline = get_line(TT.filepatch);
                if (!patchline) break;

                // Other versions of patch accept damaged patches,
                // so we need to also.
                if (!*patchline) {
                        free(patchline);
                        patchline = xstrdup(" ");
                }

                // Are we assembling a hunk?
                if (state >= 2) {
                        if (*patchline==' ' || *patchline=='+' || *patchline=='-') {
                                dlist_add(&TT.current_hunk, patchline);

                                if (*patchline != '+') TT.oldlen--;
                                if (*patchline != '-') TT.newlen--;

                                // Context line?
                                if (*patchline==' ' && state==2) TT.context++;
                                else state=3;

                                // If we've consumed all expected hunk lines, apply the hunk.

                                if (!TT.oldlen && !TT.newlen) state = apply_one_hunk();
                                continue;
                        }
                        fail_hunk();
                        state = 0;
                        continue;
                }

                // Open a new file?
                if (!strncmp("--- ", patchline, 4) || !strncmp("+++ ", patchline, 4)) {
                        char *s, **name = reverse ? &newname : &oldname;
                        int i;

                        if (*patchline == '+') {
                                name = reverse ? &oldname : &newname;
                                state = 1;
                        }

                        free(*name);
                        finish_oldfile();

                        // Trim date from end of filename (if any).  We don't care.
                        for (s = patchline+4; *s && *s!='\t'; s++)
                                if (*s=='\\' && s[1]) s++;
                        i = atoi(s);
                        if (i>1900 && i<=1970)
                                *name = xstrdup("/dev/null");
                        else {
                                *s = 0;
                                *name = xstrdup(patchline+4);
                        }

                        // We defer actually opening the file because svn produces broken
                        // patches that don't signal they want to create a new file the
                        // way the patch man page says, so you have to read the first hunk
                        // and _guess_.

                // Start a new hunk?
                } else if (state == 1 && !strncmp("@@ -", patchline, 4)) {
                        int i;

                        i = sscanf(patchline+4, "%ld,%ld +%ld,%ld", &TT.oldline,
                                                &TT.oldlen, &TT.newline, &TT.newlen);
                        if (i != 4)
                                bb_error_msg_and_die("corrupt hunk %d at %ld", TT.hunknum, TT.linenum);

                        TT.context = 0;
                        state = 2;

                        // If this is the first hunk, open the file.
                        if (TT.filein == -1) {
                                int oldsum, newsum, del = 0;
                                char *s, *name;

                                oldsum = TT.oldline + TT.oldlen;
                                newsum = TT.newline + TT.newlen;

                                name = reverse ? oldname : newname;

                                // We're deleting oldname if new file is /dev/null (before -p)
                                // or if new hunk is empty (zero context) after patching
                                if (strcmp(name, "/dev/null") == 0 || !(reverse ? oldsum : newsum)) {
                                        name = reverse ? newname : oldname;
                                        del++;
                                }

                                // handle -p path truncation.
                                for (i=0, s = name; *s;) {
                                        if ((option_mask32 & FLAG_PATHLEN) && TT.prefix == i) break;
                                        if (*(s++)=='/') {
                                                name = s;
                                                i++;
                                        }
                                }

                                if (del) {
                                        printf("removing %s\n", name);
                                        xunlink(name);
                                        state = 0;
                                // If we've got a file to open, do so.
                                } else if (!(option_mask32 & FLAG_PATHLEN) || i <= TT.prefix) {
                                        // If the old file was null, we're creating a new one.
                                        if (strcmp(oldname, "/dev/null") == 0 || !oldsum) {
                                                printf("creating %s\n", name);
                                                s = strrchr(name, '/');
                                                if (s) {
                                                        *s = 0;
                                                        xmkpath(name, -1);
                                                        *s = '/';
                                                }
                                                TT.filein = xopen(name, O_CREAT|O_EXCL|O_RDWR);
                                        } else {
                                                printf("patching file %s\n", name);
                                                TT.filein = xopen(name, O_RDWR);
                                        }
                                        TT.fileout = copy_tempfile(TT.filein, name, &TT.tempname);
                                        TT.linenum = 0;
                                        TT.hunknum = 0;
                                }
                        }

                        TT.hunknum++;

                        continue;
                }

                // If we didn't continue above, discard this line.
                free(patchline);
        }

        finish_oldfile();

        if (ENABLE_FEATURE_CLEAN_UP) {
                close(TT.filepatch);
                free(oldname);
                free(newname);
        }

        return TT.exitval;
}