#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include "malunal/strview.h"

#define STRVIEW_NUMBUF_SIZE 64

static
malunal_cstr_t
describe(malunal_int32_t code) {
  switch (code) {
  case STRVIEW_ERROR_NULL_INPUT:
    return "String view input was null.";
  case STRVIEW_ERROR_OUT_OF_RANGE:
    return "Conversion of string view to value was out of range.";
  case STRVIEW_ERROR_UNCONSUMED:
    return "String view was not consumed fully during conversion.";
  }

  return "Unknown strview error";
}

const error_domain_t ERROR_DOMAIN_STRVIEW_T = {
  .describe = &describe,
  .name     = "malunal.strview.error"
};

static malunal_size_t
strview__copy_to_buffer(
  strview_iptr_t self,
  malunal_char_t buffer[STRVIEW_NUMBUF_SIZE]
) {
  malunal_size_t length = strview_length(self);
  malunal_size_t copied =
    length >= STRVIEW_NUMBUF_SIZE - 1
      ? STRVIEW_NUMBUF_SIZE - 1
      : length;

  if (copied > 0)
    memcpy(buffer, self->beg, copied);
  buffer[copied] = '\0';
  return copied;
}


strview_t
strview(
  malunal_cstr_t data,
  malunal_size_t length
) {
  return (strview_t) {
    .beg = data,
    .end = data + length
  };
}

strview_t
strview_from_cstr(
  malunal_cstr_t data
) {
  return data != null
    ? strview(data, strlen(data))
    : strview(null, 0);
}

malunal_size_t
strview_length(
  strview_iptr_t self
) {
  return self != null
    ? self->end - self->beg
    : 0;
}

malunal_void_t
strview_ltrim(
  strview_mptr_t self,
  malunal_size_t count
) {
  malunal_size_t length =
    strview_length(self);
  if (length == 0)
    return;

  if (length < count)
    count = length;
  self->beg += count;
}

malunal_void_t
strview_rtrim(
  strview_mptr_t self,
  malunal_size_t count
) {
  malunal_size_t length =
    strview_length(self);
  if (length == 0)
    return;

  if (length < count)
    count = length;
  self->end -= count;
}

strview_t
strview_subview(
  strview_iptr_t self,
  malunal_size_t start,
  malunal_size_t count
) {
  if (self == null)
    return strview(null, 0);

  strview_t      res = { self->beg, self->end };
  malunal_size_t len = strview_length(&res);
  if (start > len)
    return strview(null, 0);

  strview_ltrim(&res, start);
  len = strview_length(&res);
  if (count > len)
    return strview(null, 0);

  strview_rtrim(&res, len - count);
  return res;
}

malunal_bool_t
strview_equals(
  strview_iptr_t self,
  strview_iptr_t other
) {
  return strview_compare(self, other) == 0;
}

malunal_int32_t
strview_compare(
  strview_iptr_t self,
  strview_iptr_t other
) {
  if (self == null || other == null) {
    if (self <  other) return -1;
    if (self >  other) return  1;
    if (self == other) return  0;
  }

  malunal_size_t hlen = strview_length(self);
  malunal_size_t nlen = strview_length(other);
  if (hlen < nlen) return -1;
  if (hlen > nlen) return  1;

  malunal_size_t smallest = hlen < nlen ? hlen : nlen;
  return strncmp(self->beg, other->beg, smallest);
}

malunal_bool_t
strview_starts_with(
  strview_iptr_t self,
  strview_iptr_t other
) {
  if (self  == null) return false;
  if (other == null) return true;

  malunal_size_t hlen = strview_length(self);
  malunal_size_t nlen = strview_length(other);
  if (nlen == 0)
    return true;

  return hlen >= nlen
    ? strncmp(self->beg, other->beg, nlen) == 0
    : false;
}

malunal_bool_t
strview_ends_with(
  strview_iptr_t self,
  strview_iptr_t other
) {
  if (self  == null) return false;
  if (other == null) return true;

  malunal_size_t hlen = strview_length(self);
  malunal_size_t nlen = strview_length(other);
  if (nlen == 0)
    return true;

  if (hlen < nlen)
    return false;

  malunal_size_t diff = hlen - nlen;
  malunal_cstr_t beg  = self->beg + diff;
  return strncmp(beg, other->beg, nlen) == 0;
}

malunal_bool_t
strview_contains(
  strview_iptr_t self,
  strview_iptr_t other
) {
  if (self  == null) return false;
  if (other == null) return true;

  malunal_size_t hlen = strview_length(self);
  malunal_size_t nlen = strview_length(other);
  if (nlen == 0)
    return true;

  if (hlen < nlen)
    return false;

  // Poor man's sliding window
  malunal_cstr_t beg = self->beg;
  while (hlen >= nlen) {
    if (strncmp(beg, other->beg, nlen) == 0)
      return true;
    beg++;
    hlen--;
  }

  return false;
}

error_t
strview_to_int64(
  strview_iptr_t   self,
  malunal_int64_t* out
) {
  if (self == null) {
    if (out != null)
      *out = 0;
    return (error_t) {
      .domain = &ERROR_DOMAIN_STRVIEW_T,
      .code   = STRVIEW_ERROR_NULL_INPUT
    };
  }

  malunal_char_t buffer[STRVIEW_NUMBUF_SIZE];
  malunal_size_t copied = strview__copy_to_buffer(self, buffer);
  if (copied == 0) {
    if (out != null)
      *out = 0;
    return (error_t) {
      .domain = &ERROR_DOMAIN_STRVIEW_T,
      .code   = STRVIEW_ERROR_UNCONSUMED
    };
  }

  malunal_str_t   endptr;
  malunal_int64_t value;

  errno = 0;
  value = strtoll(buffer, &endptr, 10);
  if (out != null)
    *out = value;

  if (errno == ERANGE)
    return (error_t) {
      .domain = &ERROR_DOMAIN_STRVIEW_T,
      .code   = STRVIEW_ERROR_OUT_OF_RANGE
    };

  return endptr != buffer + copied
    ? (error_t) {
        .domain = &ERROR_DOMAIN_STRVIEW_T,
        .code   = STRVIEW_ERROR_UNCONSUMED
      }
    : NO_ERROR;
}

error_t
strview_to_double(
  strview_iptr_t    self,
  malunal_double_t* out
) {
  if (self == null) {
    if (out != null)
      *out = 0.0;
    return (error_t) {
      .domain = &ERROR_DOMAIN_STRVIEW_T,
      .code   = STRVIEW_ERROR_NULL_INPUT
    };
  }

  malunal_char_t buffer[STRVIEW_NUMBUF_SIZE];
  malunal_size_t copied = strview__copy_to_buffer(self, buffer);
  if (copied == 0) {
    if (out != null)
      *out = 0.0;
    return (error_t) {
      .domain = &ERROR_DOMAIN_STRVIEW_T,
      .code   = STRVIEW_ERROR_UNCONSUMED
    };
  }

  malunal_str_t    endptr;
  malunal_double_t value;

  errno = 0;
  value = strtod(buffer, &endptr);
  if (out != null)
    *out = value;

  if (errno == ERANGE)
    return (error_t) {
      .domain = &ERROR_DOMAIN_STRVIEW_T,
      .code   = STRVIEW_ERROR_OUT_OF_RANGE
    };

  return endptr != buffer + copied
    ? (error_t) {
        .domain = &ERROR_DOMAIN_STRVIEW_T,
        .code   = STRVIEW_ERROR_UNCONSUMED
      }
    : NO_ERROR;
}