//
// files.c - Implementation of some file loading functionality.
//

#include <err.h>
#include <fcntl.h>
#include <limits.h>
#include <stdarg.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>

#include "files.h"
#include "match.h"
#include "pattern.h"
#include "utils.h"

//
// In the file object, populate the `lines` array with pointers to the
// beginning of each line.
//
__attribute__((nonnull))
static void populate_lines(file_t *f)
{
    // Calculate line numbers:
    size_t linecap = 10;
    f->lines = new(const char*[linecap]);
    f->nlines = 0;
    char *p = f->start;
    for (size_t n = 0; p && p <= f->end; ++n) {
        ++f->nlines;
        if (n >= linecap)
            f->lines = grow(f->lines, linecap *= 2);
        f->lines[n] = p;
        char *nl = memchr(p, '\n', (size_t)(f->end - p));
        if (nl && nl < f->end) p = nl+1;
        else break;
    }
}

//
// Read an entire file into memory, using a printf-style formatting string to
// construct the filename.
//
public file_t *load_filef(file_t **files, const char *fmt, ...)
{
    char filename[PATH_MAX+1] = {'\0'};
    va_list args;
    va_start(args, fmt);
    if (vsnprintf(filename, PATH_MAX, fmt, args) > (int)PATH_MAX)
        errx(EXIT_FAILURE, "File name is too large");
    va_end(args);
    return load_file(files, filename);
}

//
// Read an entire file into memory.
//
public file_t *load_file(file_t **files, const char *filename)
{
    int fd = filename[0] == '\0' ? STDIN_FILENO : open(filename, O_RDONLY);
    if (fd < 0) {
        // Check for <file>:<line>
        if (strrchr(filename, ':')) {
            char tmp[PATH_MAX] = {0};
            strcpy(tmp, filename);
            char *colon = strrchr(tmp, ':');
            *colon = '\0';
            file_t *f = load_file(files, tmp);
            if (!f) return f;
            long line = strtol(colon+1, &colon, 10);
            f->start = (char*)get_line(f, (size_t)line);
            f->end = (char*)get_line(f, (size_t)line+1);
            return f;
        }
        return NULL;
    }

    filename = checked_strdup(filename);
    for (const char *slashes = strstr(filename, "//"); slashes; slashes = strstr(slashes, "//"))
        memmove((char*)slashes, slashes+1, strlen(slashes+1)+1);
    file_t *f = new(file_t);
    f->filename = filename;

    struct stat sb;
    if (fstat(fd, &sb) == -1)
        goto read_file;

    f->mmapped = mmap(NULL, (size_t)sb.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
    if (f->mmapped == MAP_FAILED) {
        f->mmapped = NULL;
        goto read_file;
    }
    f->start = f->mmapped;
    f->end = &f->mmapped[sb.st_size];
    goto finished_loading;

  read_file:
    {
        size_t capacity = 1000, length = 0;
        f->allocated = new(char[capacity]);
        ssize_t just_read;
        while ((just_read=read(fd, &f->allocated[length], (capacity-1) - length)) > 0) {
            length += (size_t)just_read;
            if (length >= capacity-1)
                f->allocated = grow(f->allocated, capacity *= 2);
        }
        f->allocated[length] = '\0';
        f->start = f->allocated;
        f->end = &f->allocated[length];
    }

  finished_loading:
    if (fd != STDIN_FILENO)
        require(close(fd), "Failed to close file");

    populate_lines(f);
    if (files != NULL) {
        f->next = *files;
        *files = f;
    }
    return f;
}

//
// Set a file struct to represent a region of a different file.
//
public void slice_file(file_t *slice, file_t *src, const char *start, const char *end)
{
    memset(slice, 0, sizeof(file_t));
    slice->filename = src->filename;
    slice->lines = src->lines;
    slice->nlines = src->nlines;
    slice->start = (char*)start;
    slice->end = (char*)end;
}

//
// Create a virtual file from a string.
//
public file_t *spoof_file(file_t **files, const char *filename, const char *text, ssize_t _len)
{
    if (filename == NULL) filename = "";
    file_t *f = new(file_t);
    size_t len = _len == -1 ? strlen(text) : (size_t)_len;
    f->filename = checked_strdup(filename);
    f->allocated = new(char[len+1]);
    memcpy(f->allocated, text, len);
    f->start = &f->allocated[0];
    f->end = &f->allocated[len];
    populate_lines(f);
    if (files != NULL) {
        f->next = *files;
        *files = f;
    }
    return f;
}

//
// Free a file and all memory contained inside its members, then set the input
// pointer to NULL.
//
public void destroy_file(file_t **at_f)
{
    file_t *f = (file_t*)*at_f;
    if (f->filename)
        delete(&f->filename);

    if (f->lines)
        delete(&f->lines);

    if (f->allocated)
        delete(&f->allocated);

    if (f->mmapped) {
        require(munmap(f->mmapped, (size_t)(f->end - f->mmapped)),
                          "Failure to un-memory-map some memory");
        f->mmapped = NULL;
    }

    delete(at_f);
}

//
// Given a pointer, determine which line number it points to.
//
public size_t get_line_number(file_t *f, const char *p)
{
    if (f->nlines == 0) return 0;
    // Binary search:
    size_t lo = 0, hi = f->nlines-1;
    while (lo <= hi) {
        size_t mid = (lo + hi) / 2;
        if (f->lines[mid] == p)
            return mid + 1;
        else if (f->lines[mid] < p)
            lo = mid + 1;    
        else if (f->lines[mid] > p)
            hi = mid - 1;
    }
    return lo; // Return the line number whose line starts closest before p
}

//
// Given a pointer, determine which line column it points to.
//
public size_t get_line_column(file_t *f, const char *p)
{
    size_t line_no = get_line_number(f, p);
    return 1 + (size_t)(p - f->lines[line_no]);
}

//
// Return a pointer to the line with the specified line number.
//
public const char *get_line(file_t *f, size_t line_number)
{
    if (line_number == 0 || line_number > f->nlines) return NULL;
    return f->lines[line_number - 1];
}

// vim: ts=4 sw=0 et cino=L2,l1,(0,W4,m1,\:0