#include <ctype.h>
#include <errno.h>
#include <memory.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "malunal/version.h"


static
malunal_cstr_t
describe(malunal_int32_t code) {
  switch (code) {
  case VERSION_ERROR_NULL_INPUT:
    return "Version input or output pointer was null.";
  case VERSION_ERROR_INVALID_NUMBER:
    return "Expected a numeric version component but found none, or trailing "
           "characters remained after it.";
  case VERSION_ERROR_UNEXPECTED_CHAR:
    return "An unexpected character was encountered while parsing the version.";
  case VERSION_ERROR_MISSING_PART:
    return "The version string was missing one of its required parts.";
  case VERSION_ERROR_LEADING_ZERO:
    return "A numeric version component had a disallowed leading zero.";
  case VERSION_ERROR_VALUE_OVERFLOW:
    return "A numeric version component was too large to represent.";
  }

  return "Unknown version error";
}

const error_domain_t ERROR_DOMAIN_VERSION_T = {
  .describe = &describe,
  .name     = "malunal.version.error"
};


static
error_t
parse_core_number(
  strview_mptr_t  verstr,
  malunal_size_t* outval
) {
  if (!isdigit((unsigned char)*verstr->beg))
    return (error_t) {
      .domain = &ERROR_DOMAIN_VERSION_T,
      .code   = VERSION_ERROR_INVALID_NUMBER
    };

  malunal_cstr_t start = verstr->beg;
  while (isdigit((unsigned char)*verstr->beg))
    verstr->beg++;

  if (*verstr->beg != '.')
    return (error_t) {
      .domain = &ERROR_DOMAIN_VERSION_T,
      .code   = !(
        strview_length(verstr) == 0   ||
        *verstr->beg           == '-' ||
        *verstr->beg           == '+' ||
        *verstr->beg           == '.'
      ) ? VERSION_ERROR_UNEXPECTED_CHAR
        : VERSION_ERROR_MISSING_PART
    };

  if (verstr->beg - start > 1 && start[0] == '0')
    return (error_t) {
      .domain = &ERROR_DOMAIN_VERSION_T,
      .code   = VERSION_ERROR_LEADING_ZERO
    };

  strview_t       walked = { start, verstr->beg };
  malunal_int64_t value  = 0;
  error_t         result = strview_to_int64(&walked, &value);
  if (result.domain == &ERROR_DOMAIN_STRVIEW_T) {
    if (result.code == STRVIEW_ERROR_OUT_OF_RANGE)
      return (error_t) {
        .domain = &ERROR_DOMAIN_VERSION_T,
        .code   = VERSION_ERROR_VALUE_OVERFLOW
      };

    if (result.code == STRVIEW_ERROR_UNCONSUMED)
      return (error_t) {
        .domain = &ERROR_DOMAIN_VERSION_T,
        .code   = VERSION_ERROR_INVALID_NUMBER
      };
  }

  *outval = (malunal_size_t)value;
  return NO_ERROR;
}

static
error_t
parse_patch_number(
  strview_mptr_t  verstr,
  malunal_size_t* outval
) {
  if (!isdigit((unsigned char)*verstr->beg))
    return (error_t) {
      .domain = &ERROR_DOMAIN_VERSION_T,
      .code   = VERSION_ERROR_INVALID_NUMBER
    };

  malunal_cstr_t start = verstr->beg;
  while (isdigit((unsigned char)*verstr->beg))
    verstr->beg++;

  if (
    strview_length(verstr) != 0   &&
    *verstr->beg           != '-' &&
    *verstr->beg           != '+'
  ) return (error_t) {
      .domain = &ERROR_DOMAIN_VERSION_T,
      .code   = VERSION_ERROR_UNEXPECTED_CHAR
    };

  if (verstr->beg - start > 1 && start[0] == '0')
    return (error_t) {
      .domain = &ERROR_DOMAIN_VERSION_T,
      .code   = VERSION_ERROR_LEADING_ZERO
    };

  strview_t       walked = { start, verstr->beg };
  malunal_int64_t value  = 0;
  error_t         result = strview_to_int64(&walked, &value);
  if (result.domain == &ERROR_DOMAIN_STRVIEW_T) {
    if (result.code == STRVIEW_ERROR_OUT_OF_RANGE)
      return (error_t) {
        .domain = &ERROR_DOMAIN_VERSION_T,
        .code   = VERSION_ERROR_VALUE_OVERFLOW
      };

    if (result.code == STRVIEW_ERROR_UNCONSUMED)
      return (error_t) {
        .domain = &ERROR_DOMAIN_VERSION_T,
        .code   = VERSION_ERROR_INVALID_NUMBER
      };
  }

  *outval = (malunal_size_t)value;
  return NO_ERROR;
}

static
error_t
parse_preview_string(
  strview_mptr_t verstr,
  strview_mptr_t outstr
) {
  if (*verstr->beg != '-')
    return NO_ERROR;

  malunal_cstr_t start = ++verstr->beg;
  if (strview_length(verstr) == 0 || *verstr->beg == '+')
    return (error_t) {
      .domain = &ERROR_DOMAIN_VERSION_T,
      .code   = VERSION_ERROR_MISSING_PART
    };

  while (strview_length(verstr) && *verstr->beg != '+')
    verstr->beg++;

  *outstr = (strview_t) {
    .beg = start,
    .end = verstr->beg
  };
  return NO_ERROR;
}

static
error_t
parse_build_string(
  strview_mptr_t verstr,
  strview_mptr_t outstr
) {
  if (*verstr->beg != '+')
    return NO_ERROR;

  malunal_cstr_t start = ++verstr->beg;
  if (strview_length(verstr) == 0)
    return (error_t) {
      .domain = &ERROR_DOMAIN_VERSION_T,
      .code   = VERSION_ERROR_MISSING_PART
    };

  while (strview_length(verstr) != 0)
    verstr->beg++;

  *outstr = (strview_t) {
    .beg = start,
    .end = verstr->beg
  };

  return NO_ERROR;
}

error_t
parse_version(
  strview_iptr_t verstr,
  version_mptr_t out
) {
  if (verstr == null)
    return (error_t) {
      .domain = &ERROR_DOMAIN_VERSION_T,
      .code   = VERSION_ERROR_NULL_INPUT
    };

  if (out == null)
    return (error_t) {
      .domain = &ERROR_DOMAIN_VERSION_T,
      .code   = VERSION_ERROR_NULL_INPUT
    };

  memset(out, 0, sizeof(version_t));
  if (verstr->beg == null)
    return NO_ERROR;

  error_t   result;
  strview_t tempstr = {
    .beg = verstr->beg,
    .end = verstr->end
  };

  result = parse_core_number(&tempstr, &out->major);
  if (result.domain != null)
    return result;

  tempstr.beg++;
  result = parse_core_number(&tempstr, &out->minor);
  if (result.domain != null)
    return result;

  tempstr.beg++;
  result = parse_patch_number(&tempstr, &out->patch);
  if (result.domain != null)
    return result;

  result = parse_preview_string(&tempstr, &out->preview);
  if (result.domain != null)
    return result;

  result = parse_build_string(&tempstr, &out->build);
  if (result.domain != null)
    return result;

  if (strview_length(&tempstr) != 0)
    return (error_t) {
      .domain = &ERROR_DOMAIN_VERSION_T,
      .code   = VERSION_ERROR_UNEXPECTED_CHAR
    };

  return NO_ERROR;
}

static
malunal_bool_t
identifier_is_numeric(strview_iptr_t id) {
  if (strview_length(id) == 0)
    return false;

  malunal_cstr_t p;
  for (p = id->beg; p < id->end; p++)
    if (!isdigit(*p))
      return false;
  return true;
}

static
malunal_int32_t
compare_numeric_identifier(
  strview_iptr_t a,
  strview_iptr_t b
) {
  malunal_size_t alen = strview_length(a);
  malunal_size_t blen = strview_length(b);
  malunal_cstr_t ap   = a->beg;
  malunal_cstr_t bp   = b->beg;

  // Ignore leading zeros so two differently-padded numbers compare fairly.
  while (alen > 1 && *ap == '0') { ap++; alen--; }
  while (blen > 1 && *bp == '0') { bp++; blen--; }

  if (alen != blen) return alen < blen ? -1 : 1;
  if (alen == 0)    return 0;

  malunal_int32_t cmp = strncmp(ap, bp, alen);
  return cmp < 0 ? -1 : (cmp > 0 ? 1 : 0);
}

static
malunal_int32_t
compare_alphanumeric_identifier(
  strview_iptr_t a,
  strview_iptr_t b
) {
  malunal_size_t  alen   = strview_length(a);
  malunal_size_t  blen   = strview_length(b);
  malunal_size_t  minlen = alen < blen ? alen : blen;
  malunal_int32_t cmp    = minlen > 0
    ? strncmp(a->beg, b->beg, (size_t)minlen)
    : 0;

  if (cmp != 0)
    return cmp < 0 ? -1 : 1;

  return alen != blen
    ? alen < blen ? -1 : 1
    : 0;
}

static
malunal_int32_t
compare_preview_identifier(
  strview_iptr_t a,
  strview_iptr_t b
) {
  malunal_bool_t anum = identifier_is_numeric(a);
  malunal_bool_t bnum = identifier_is_numeric(b);
  if (anum && bnum)
    return compare_numeric_identifier(a, b);

  // Per semver, numeric identifiers always have lower precedence than
  // alphanumeric ones.
  return anum == bnum
    ? compare_alphanumeric_identifier(a, b)
    : anum ? -1 : 1;
}

static
malunal_int32_t
compare_preview(
  strview_iptr_t self,
  strview_iptr_t other
) {
  strview_t sremain = *self;
  strview_t oremain = *other;

  for (;;) {
    malunal_bool_t sdone = strview_length(&sremain) == 0;
    malunal_bool_t odone = strview_length(&oremain) == 0;
    if (sdone && odone)
      return 0;

    // A pre-release with fewer identifiers has lower precedence, as long as
    // all the preceding identifiers matched.
    if (sdone) return -1;
    if (odone) return  1;

    malunal_cstr_t send = sremain.beg;
    while (send < sremain.end && *send != '.')
      send++;
    strview_t sid = { sremain.beg, send };

    malunal_cstr_t oend = oremain.beg;
    while (oend < oremain.end && *oend != '.')
      oend++;
    strview_t oid = { oremain.beg, oend };

    malunal_int32_t cmp = compare_preview_identifier(&sid, &oid);
    if (cmp != 0)
      return cmp;

    sremain.beg = send < sremain.end ? send + 1 : send;
    oremain.beg = oend < oremain.end ? oend + 1 : oend;
  }
}

malunal_int32_t
version_compare(
  version_iptr_t self,
  version_iptr_t other
) {
  if (self  == other) return  0;
  if (self  == null)  return -1;
  if (other == null)  return  1;

  if (self->major != other->major) return self->major < other->major ? -1 : 1;
  if (self->minor != other->minor) return self->minor < other->minor ? -1 : 1;
  if (self->patch != other->patch) return self->patch < other->patch ? -1 : 1;

  malunal_bool_t self_has_preview  = strview_length(&self->preview)  != 0;
  malunal_bool_t other_has_preview = strview_length(&other->preview) != 0;
  if (self_has_preview != other_has_preview)
    return self_has_preview ? -1 : 1;

  return self_has_preview
    ? compare_preview(&self->preview, &other->preview)
    : 0;
}

malunal_int32_t
version_string(
  version_iptr_t self,
  malunal_str_t  buffer,
  malunal_size_t length
) {
  if (self == null || buffer == null || length == 0)
    return -1;

  malunal_size_t written = snprintf(
    buffer,
    length,
    "%llu.%llu.%llu",
    self->major,
    self->minor,
    self->patch
  );

  if (written < 0 || written >= length)
    return -1;

  malunal_size_t preview_len =
    strview_length(&self->preview);
  if (preview_len > 0) {
    malunal_int32_t n = snprintf(
      buffer + written,
      length - written,
      "-%.*s",
      preview_len,
      self->preview.beg
    );

    if (n < 0 || (written + n) >= length)
      return -1;
    written += n;
  }

  malunal_size_t build_len =
    strview_length(&self->build);
  if (build_len > 0) {
    malunal_int32_t n = snprintf(
      buffer + written,
      length - written,
      "+%.*s",
      build_len,
      self->build.beg
    );

    if (n < 0 || (written + n) >= length)
      return -1;
    written += n;
  }

  return written;
}