#define _POSIX_C_SOURCE 200809L

#include "amduat/asl/artifact_io.h"
#include "amduat/asl/asl_store_fs.h"
#include "amduat/asl/asl_store_fs_meta.h"
#include "amduat/asl/ref_text.h"
#include "amduat/asl/store.h"
#include "amduat/enc/asl1_core_codec.h"

#include <errno.h>
#include <signal.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <string.h>

#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/un.h>
#include <unistd.h>

static const char *const AMDUATD_DEFAULT_ROOT = ".amduat-asl";
static const char *const AMDUATD_DEFAULT_SOCK = "amduatd.sock";

static volatile sig_atomic_t amduatd_should_exit = 0;

static void amduatd_on_signal(int signo) {
  (void)signo;
  amduatd_should_exit = 1;
}

static bool amduatd_write_all(int fd, const uint8_t *buf, size_t len) {
  size_t off = 0;
  while (off < len) {
    ssize_t n = write(fd, buf + off, len - off);
    if (n < 0) {
      if (errno == EINTR) {
        continue;
      }
      return false;
    }
    if (n == 0) {
      return false;
    }
    off += (size_t)n;
  }
  return true;
}

static bool amduatd_read_exact(int fd, uint8_t *buf, size_t len) {
  size_t off = 0;
  while (off < len) {
    ssize_t n = read(fd, buf + off, len - off);
    if (n < 0) {
      if (errno == EINTR) {
        continue;
      }
      return false;
    }
    if (n == 0) {
      return false;
    }
    off += (size_t)n;
  }
  return true;
}

static bool amduatd_read_line(int fd, char *buf, size_t cap, size_t *out_len) {
  size_t len = 0;
  while (len + 1 < cap) {
    char c = 0;
    ssize_t n = read(fd, &c, 1);
    if (n < 0) {
      if (errno == EINTR) {
        continue;
      }
      return false;
    }
    if (n == 0) {
      return false;
    }
    if (c == '\n') {
      break;
    }
    buf[len++] = c;
  }
  if (len == 0) {
    return false;
  }
  if (len > 0 && buf[len - 1] == '\r') {
    len--;
  }
  buf[len] = '\0';
  if (out_len != NULL) {
    *out_len = len;
  }
  return true;
}

typedef struct {
  char method[8];
  char path[1024];
  char content_type[128];
  char accept[128];
  char x_type_tag[64];
  size_t content_length;
} amduatd_http_req_t;

static void amduatd_http_req_init(amduatd_http_req_t *req) {
  memset(req, 0, sizeof(*req));
}

static bool amduatd_http_parse_request(int fd, amduatd_http_req_t *out_req) {
  char line[2048];
  size_t line_len = 0;
  char *sp1 = NULL;
  char *sp2 = NULL;

  if (out_req == NULL) {
    return false;
  }
  amduatd_http_req_init(out_req);

  if (!amduatd_read_line(fd, line, sizeof(line), &line_len)) {
    return false;
  }

  sp1 = strchr(line, ' ');
  if (sp1 == NULL) {
    return false;
  }
  *sp1++ = '\0';
  sp2 = strchr(sp1, ' ');
  if (sp2 == NULL) {
    return false;
  }
  *sp2++ = '\0';

  if (strlen(line) >= sizeof(out_req->method)) {
    return false;
  }
  strncpy(out_req->method, line, sizeof(out_req->method) - 1);

  if (strlen(sp1) >= sizeof(out_req->path)) {
    return false;
  }
  strncpy(out_req->path, sp1, sizeof(out_req->path) - 1);

  for (;;) {
    if (!amduatd_read_line(fd, line, sizeof(line), &line_len)) {
      return false;
    }
    if (line_len == 0) {
      break;
    }

    if (strncasecmp(line, "Content-Length:", 15) == 0) {
      const char *v = line + 15;
      while (*v == ' ' || *v == '\t') {
        v++;
      }
      out_req->content_length = (size_t)strtoull(v, NULL, 10);
    } else if (strncasecmp(line, "Content-Type:", 13) == 0) {
      const char *v = line + 13;
      while (*v == ' ' || *v == '\t') {
        v++;
      }
      strncpy(out_req->content_type, v, sizeof(out_req->content_type) - 1);
    } else if (strncasecmp(line, "Accept:", 7) == 0) {
      const char *v = line + 7;
      while (*v == ' ' || *v == '\t') {
        v++;
      }
      strncpy(out_req->accept, v, sizeof(out_req->accept) - 1);
    } else if (strncasecmp(line, "X-Amduat-Type-Tag:", 18) == 0) {
      const char *v = line + 18;
      while (*v == ' ' || *v == '\t') {
        v++;
      }
      strncpy(out_req->x_type_tag, v, sizeof(out_req->x_type_tag) - 1);
    }
  }

  return true;
}

static bool amduatd_http_send_status(int fd,
                                     int code,
                                     const char *reason,
                                     const char *content_type,
                                     const uint8_t *body,
                                     size_t body_len,
                                     bool head_only) {
  char hdr[512];
  int n = snprintf(hdr,
                   sizeof(hdr),
                   "HTTP/1.1 %d %s\r\n"
                   "Content-Length: %zu\r\n"
                   "Content-Type: %s\r\n"
                   "Connection: close\r\n"
                   "\r\n",
                   code,
                   reason != NULL ? reason : "",
                   body_len,
                   content_type != NULL ? content_type : "text/plain");
  if (n <= 0 || (size_t)n >= sizeof(hdr)) {
    return false;
  }
  if (!amduatd_write_all(fd, (const uint8_t *)hdr, (size_t)n)) {
    return false;
  }
  if (!head_only && body != NULL && body_len != 0) {
    return amduatd_write_all(fd, body, body_len);
  }
  return true;
}

static bool amduatd_http_send_text(int fd,
                                   int code,
                                   const char *reason,
                                   const char *text,
                                   bool head_only) {
  const uint8_t *body = (const uint8_t *)(text != NULL ? text : "");
  size_t len = text != NULL ? strlen(text) : 0;
  return amduatd_http_send_status(
      fd, code, reason, "text/plain; charset=utf-8", body, len, head_only);
}

static bool amduatd_http_send_json(int fd,
                                   int code,
                                   const char *reason,
                                   const char *json,
                                   bool head_only) {
  const uint8_t *body = (const uint8_t *)(json != NULL ? json : "{}");
  size_t len = json != NULL ? strlen(json) : 2;
  return amduatd_http_send_status(
      fd, code, reason, "application/json", body, len, head_only);
}

static const char *amduatd_query_param(const char *path,
                                       const char *key,
                                       char *out_value,
                                       size_t out_cap) {
  const char *q = strchr(path, '?');
  size_t key_len = 0;
  if (out_value != NULL && out_cap != 0) {
    out_value[0] = '\0';
  }
  if (q == NULL || key == NULL || out_value == NULL || out_cap == 0) {
    return NULL;
  }
  q++;
  key_len = strlen(key);

  while (*q != '\0') {
    const char *k = q;
    const char *eq = strchr(k, '=');
    const char *amp = strchr(k, '&');
    size_t klen = 0;
    const char *v = NULL;
    size_t vlen = 0;

    if (amp == NULL) {
      amp = q + strlen(q);
    }
    if (eq == NULL || eq > amp) {
      q = (*amp == '&') ? (amp + 1) : amp;
      continue;
    }
    klen = (size_t)(eq - k);
    if (klen == key_len && strncmp(k, key, key_len) == 0) {
      v = eq + 1;
      vlen = (size_t)(amp - v);
      if (vlen >= out_cap) {
        vlen = out_cap - 1;
      }
      memcpy(out_value, v, vlen);
      out_value[vlen] = '\0';
      return out_value;
    }
    q = (*amp == '&') ? (amp + 1) : amp;
  }

  return NULL;
}

static void amduatd_path_without_query(const char *path,
                                       char *out,
                                       size_t cap) {
  const char *q = NULL;
  size_t n = 0;
  if (out == NULL || cap == 0) {
    return;
  }
  out[0] = '\0';
  if (path == NULL) {
    return;
  }
  q = strchr(path, '?');
  n = q != NULL ? (size_t)(q - path) : strlen(path);
  if (n >= cap) {
    n = cap - 1;
  }
  memcpy(out, path, n);
  out[n] = '\0';
}

static bool amduatd_parse_type_tag_hex(const char *text,
                                       bool *out_has_type_tag,
                                       amduat_type_tag_t *out_type_tag) {
  char *end = NULL;
  unsigned long v = 0;
  if (out_has_type_tag != NULL) {
    *out_has_type_tag = false;
  }
  if (text == NULL || text[0] == '\0' || out_type_tag == NULL ||
      out_has_type_tag == NULL) {
    return true;
  }
  errno = 0;
  v = strtoul(text, &end, 0);
  if (errno != 0 || end == text || *end != '\0' || v > 0xffffffffUL) {
    return false;
  }
  *out_has_type_tag = true;
  out_type_tag->tag_id = (uint32_t)v;
  return true;
}

static bool amduatd_handle_meta(int fd,
                                const amduat_asl_store_fs_config_t *cfg,
                                bool head_only) {
  char json[512];
  int n = snprintf(json,
                   sizeof(json),
                   "{"
                   "\"store_id\":\"%s\","
                   "\"encoding_profile_id\":\"0x%04x\","
                   "\"hash_id\":\"0x%04x\""
                   "}\n",
                   cfg != NULL ? cfg->store_id : "",
                   cfg != NULL ? (unsigned int)cfg->config.encoding_profile_id
                               : 0u,
                   cfg != NULL ? (unsigned int)cfg->config.hash_id : 0u);
  if (n <= 0 || (size_t)n >= sizeof(json)) {
    return amduatd_http_send_text(fd, 500, "Internal Server Error", "error\n",
                                 head_only);
  }
  return amduatd_http_send_json(fd, 200, "OK", json, head_only);
}

static bool amduatd_handle_get_artifact(int fd,
                                        amduat_asl_store_t *store,
                                        const char *path,
                                        bool head_only) {
  char no_query[1024];
  char format[32];
  const char *ref_text = NULL;
  amduat_reference_t ref;
  amduat_artifact_t artifact;
  amduat_asl_store_error_t err;
  bool want_artifact = false;

  memset(&ref, 0, sizeof(ref));
  memset(&artifact, 0, sizeof(artifact));
  amduatd_path_without_query(path, no_query, sizeof(no_query));

  if (strncmp(no_query, "/v1/artifacts/", 14) != 0) {
    return amduatd_http_send_text(fd, 404, "Not Found", "not found\n",
                                 head_only);
  }
  ref_text = no_query + 14;
  if (ref_text[0] == '\0') {
    return amduatd_http_send_text(fd, 400, "Bad Request", "missing ref\n",
                                 head_only);
  }

  if (!amduat_asl_ref_decode_hex(ref_text, &ref)) {
    return amduatd_http_send_text(fd, 400, "Bad Request", "invalid ref\n",
                                 head_only);
  }

  memset(format, 0, sizeof(format));
  if (amduatd_query_param(path, "format", format, sizeof(format)) != NULL) {
    if (strcmp(format, "artifact") == 0) {
      want_artifact = true;
    } else if (strcmp(format, "raw") == 0 || format[0] == '\0') {
      want_artifact = false;
    } else {
      free((void *)ref.digest.data);
      return amduatd_http_send_text(fd, 400, "Bad Request",
                                   "invalid format\n", head_only);
    }
  }

  err = amduat_asl_store_get(store, ref, &artifact);
  free((void *)ref.digest.data);
  if (err == AMDUAT_ASL_STORE_ERR_NOT_FOUND) {
    return amduatd_http_send_text(fd, 404, "Not Found", "not found\n",
                                 head_only);
  }
  if (err != AMDUAT_ASL_STORE_OK) {
    amduat_asl_artifact_free(&artifact);
    return amduatd_http_send_text(fd, 500, "Internal Server Error",
                                 "store error\n", head_only);
  }

  if (!want_artifact) {
    bool ok = amduatd_http_send_status(
        fd,
        200,
        "OK",
        "application/octet-stream",
        artifact.bytes.data,
        artifact.bytes.len,
        head_only);
    amduat_asl_artifact_free(&artifact);
    return ok;
  }

  {
    amduat_octets_t out = amduat_octets(NULL, 0);
    bool ok = amduat_enc_asl1_core_encode_artifact_v1(artifact, &out);
    amduat_asl_artifact_free(&artifact);
    if (!ok) {
      return amduatd_http_send_text(fd, 500, "Internal Server Error",
                                   "encode error\n", head_only);
    }
    ok = amduatd_http_send_status(fd,
                                 200,
                                 "OK",
                                 "application/vnd.amduat.asl.artifact+v1",
                                 out.data,
                                 out.len,
                                 head_only);
    free((void *)out.data);
    return ok;
  }
}

static bool amduatd_handle_head_artifact(int fd,
                                         amduat_asl_store_t *store,
                                         const char *path) {
  return amduatd_handle_get_artifact(fd, store, path, true);
}

static bool amduatd_handle_post_artifacts(int fd,
                                          amduat_asl_store_t *store,
                                          const amduatd_http_req_t *req) {
  uint8_t *body = NULL;
  bool has_type_tag = false;
  amduat_type_tag_t type_tag;
  amduat_asl_io_format_t input_format = AMDUAT_ASL_IO_RAW;
  amduat_artifact_t artifact;
  amduat_reference_t ref;
  amduat_asl_store_error_t err;
  char *ref_hex = NULL;
  char json[2048];

  memset(&artifact, 0, sizeof(artifact));
  memset(&ref, 0, sizeof(ref));
  memset(&type_tag, 0, sizeof(type_tag));

  if (req == NULL) {
    return amduatd_http_send_text(fd, 400, "Bad Request", "bad request\n",
                                 false);
  }

  if (req->content_length > (64u * 1024u * 1024u)) {
    return amduatd_http_send_text(fd, 413, "Payload Too Large",
                                 "payload too large\n", false);
  }

  if (req->content_length != 0) {
    body = (uint8_t *)malloc(req->content_length);
    if (body == NULL) {
      return amduatd_http_send_text(fd, 500, "Internal Server Error",
                                   "oom\n", false);
    }
    if (!amduatd_read_exact(fd, body, req->content_length)) {
      free(body);
      return false;
    }
  } else {
    body = NULL;
  }

  if (req->content_type[0] != '\0' &&
      strstr(req->content_type, "application/vnd.amduat.asl.artifact+v1") !=
          NULL) {
    input_format = AMDUAT_ASL_IO_ARTIFACT;
  }

  if (input_format == AMDUAT_ASL_IO_RAW) {
    if (!amduatd_parse_type_tag_hex(req->x_type_tag,
                                   &has_type_tag,
                                   &type_tag)) {
      free(body);
      return amduatd_http_send_text(fd, 400, "Bad Request",
                                   "invalid X-Amduat-Type-Tag\n", false);
    }
  }

  if (!amduat_asl_artifact_from_bytes(amduat_octets(body, req->content_length),
                                      input_format,
                                      has_type_tag,
                                      type_tag,
                                      &artifact)) {
    free(body);
    return amduatd_http_send_text(fd, 400, "Bad Request",
                                 "invalid artifact\n", false);
  }

  err = amduat_asl_store_put(store, artifact, &ref);
  amduat_asl_artifact_free(&artifact);
  if (err != AMDUAT_ASL_STORE_OK) {
    free((void *)ref.digest.data);
    return amduatd_http_send_text(fd, 500, "Internal Server Error",
                                 "store error\n", false);
  }

  if (!amduat_asl_ref_encode_hex(ref, &ref_hex)) {
    free((void *)ref.digest.data);
    return amduatd_http_send_text(fd, 500, "Internal Server Error",
                                 "encode ref error\n", false);
  }
  free((void *)ref.digest.data);

  {
    int n = snprintf(json, sizeof(json), "{\"ref\":\"%s\"}\n", ref_hex);
    free(ref_hex);
    if (n <= 0 || (size_t)n >= sizeof(json)) {
      return amduatd_http_send_text(fd, 500, "Internal Server Error",
                                   "error\n", false);
    }
    return amduatd_http_send_json(fd, 200, "OK", json, false);
  }
}

static bool amduatd_handle_conn(int fd,
                                amduat_asl_store_t *store,
                                const amduat_asl_store_fs_config_t *cfg) {
  amduatd_http_req_t req;
  char no_query[1024];

  if (!amduatd_http_parse_request(fd, &req)) {
    return false;
  }

  amduatd_path_without_query(req.path, no_query, sizeof(no_query));

  if (strcmp(req.method, "GET") == 0 && strcmp(no_query, "/v1/meta") == 0) {
    return amduatd_handle_meta(fd, cfg, false);
  }
  if (strcmp(req.method, "HEAD") == 0 && strcmp(no_query, "/v1/meta") == 0) {
    return amduatd_handle_meta(fd, cfg, true);
  }

  if (strcmp(req.method, "POST") == 0 && strcmp(no_query, "/v1/artifacts") == 0) {
    return amduatd_handle_post_artifacts(fd, store, &req);
  }
  if (strcmp(req.method, "GET") == 0 &&
      strncmp(no_query, "/v1/artifacts/", 14) == 0) {
    return amduatd_handle_get_artifact(fd, store, req.path, false);
  }
  if (strcmp(req.method, "HEAD") == 0 &&
      strncmp(no_query, "/v1/artifacts/", 14) == 0) {
    return amduatd_handle_head_artifact(fd, store, req.path);
  }

  return amduatd_http_send_text(fd, 404, "Not Found", "not found\n", false);
}

static void amduatd_print_usage(FILE *stream) {
  fprintf(stream,
          "usage:\n"
          "  amduatd [--root PATH] [--sock PATH]\n"
          "\n"
          "defaults:\n"
          "  --root %s\n"
          "  --sock %s\n",
          AMDUATD_DEFAULT_ROOT,
          AMDUATD_DEFAULT_SOCK);
}

int main(int argc, char **argv) {
  const char *root = AMDUATD_DEFAULT_ROOT;
  const char *sock_path = AMDUATD_DEFAULT_SOCK;
  amduat_asl_store_fs_config_t cfg;
  amduat_asl_store_fs_t fs;
  amduat_asl_store_t store;
  int i;
  int sfd = -1;

  for (i = 1; i < argc; ++i) {
    if (strcmp(argv[i], "--root") == 0) {
      if (i + 1 >= argc) {
        fprintf(stderr, "error: --root requires a path\n");
        return 2;
      }
      root = argv[++i];
    } else if (strcmp(argv[i], "--sock") == 0) {
      if (i + 1 >= argc) {
        fprintf(stderr, "error: --sock requires a path\n");
        return 2;
      }
      sock_path = argv[++i];
    } else if (strcmp(argv[i], "--help") == 0 || strcmp(argv[i], "-h") == 0) {
      amduatd_print_usage(stdout);
      return 0;
    } else {
      fprintf(stderr, "error: unknown option: %s\n", argv[i]);
      return 2;
    }
  }

  memset(&cfg, 0, sizeof(cfg));
  if (!amduat_asl_store_fs_load_config(root, &cfg)) {
    fprintf(stderr, "error: failed to load store config: %s\n", root);
    return 8;
  }

  memset(&fs, 0, sizeof(fs));
  if (!amduat_asl_store_fs_init(&fs, cfg.config, root)) {
    fprintf(stderr, "error: failed to initialize store: %s\n", root);
    return 8;
  }
  amduat_asl_store_init(&store, cfg.config, amduat_asl_store_fs_ops(), &fs);

  signal(SIGINT, amduatd_on_signal);
  signal(SIGTERM, amduatd_on_signal);

  sfd = socket(AF_UNIX, SOCK_STREAM, 0);
  if (sfd < 0) {
    perror("socket");
    return 8;
  }

  {
    struct sockaddr_un addr;
    memset(&addr, 0, sizeof(addr));
    addr.sun_family = AF_UNIX;
    if (strlen(sock_path) >= sizeof(addr.sun_path)) {
      fprintf(stderr, "error: socket path too long\n");
      close(sfd);
      return 2;
    }
    strncpy(addr.sun_path, sock_path, sizeof(addr.sun_path) - 1);

    (void)unlink(sock_path);

    if (bind(sfd, (struct sockaddr *)&addr, sizeof(addr)) < 0) {
      perror("bind");
      close(sfd);
      return 8;
    }
    (void)chmod(sock_path, 0660);

    if (listen(sfd, 16) < 0) {
      perror("listen");
      (void)unlink(sock_path);
      close(sfd);
      return 8;
    }
  }

  fprintf(stderr, "amduatd: root=%s sock=%s\n", root, sock_path);

  while (!amduatd_should_exit) {
    int cfd = accept(sfd, NULL, NULL);
    if (cfd < 0) {
      if (errno == EINTR) {
        continue;
      }
      perror("accept");
      break;
    }

    (void)amduatd_handle_conn(cfd, &store, &cfg);
    (void)close(cfd);
  }

  (void)unlink(sock_path);
  (void)close(sfd);
  return 0;
}