#include <math.h>

#include "lander.h"

/*
 * Converts a string to a number, returning true if the string contained a valid
 * positive number.
 */
static bool string_to_num(size_t *res, const char *s, size_t len) {
  *res = 0;

  for (size_t i = 0; i < len; i++) {
    int val = s[i] - '0';

    if (val < 0 || val > 9) {
      return false;
    }

    *res += val * (int)pow(10, (len - 1) - i);
  }

  return true;
}

/*
 * Try to find and parse the Content-Length header. This function returns true
 * if it was successful. If false is returned, the underlying step should
 * immediately exit.
 */
static bool try_parse_content_length(event_loop_conn *conn) {
  http_loop_ctx *ctx = conn->ctx;

  for (size_t i = 0; i < ctx->req.num_headers; i++) {
    struct phr_header *header = &ctx->req.headers[i];

    if (strncmp(header->name, "Content-Length", header->name_len) == 0) {
      // If the content length header is present but contains an invalid
      // number, we return a bad request error
      if (!string_to_num(&ctx->req.body.expected_len, header->value,
                         header->value_len)) {
        ctx->res.status = http_bad_request;
        conn->state = event_loop_conn_state_res;

        return false;
      }
      // The content length was actually 0, so we can instantly return here
      else if (ctx->req.body.expected_len == 0) {
        return false;
      }
    }
  }

  // A zero here means there's no content length header
  if (ctx->req.body.expected_len == 0) {
    ctx->res.status = http_length_required;
    conn->state = event_loop_conn_state_res;

    return false;
  }

  return true;
}

bool http_loop_step_body_to_buf(event_loop_conn *conn) {
  http_loop_ctx *ctx = conn->ctx;

  if (ctx->req.body.expected_len == 0) {
    if (!try_parse_content_length(conn)) {
      return true;
    }

    ctx->req.body.type = http_body_buf;
    ctx->req.body.buf = malloc(ctx->req.body.expected_len * sizeof(uint8_t));
    ctx->req.body.len = 0;
  }

  size_t bytes_to_copy = MIN(conn->rbuf_size - conn->rbuf_read,
                             ctx->req.body.expected_len - ctx->req.body.len);
  memcpy(&ctx->req.body.buf[ctx->req.body.len], &conn->rbuf[conn->rbuf_read],
         bytes_to_copy);
  ctx->req.body.len += bytes_to_copy;
  conn->rbuf_read += bytes_to_copy;

  return ctx->req.body.len == ctx->req.body.expected_len;
}

bool http_loop_step_body_to_file(event_loop_conn *conn) {
  http_loop_ctx *ctx = conn->ctx;

  if (ctx->req.body.expected_len == 0) {
    if (!try_parse_content_length(conn)) {
      return true;
    }

    ctx->req.body.type = http_body_file;
    ctx->req.body.file = fopen(ctx->req.body.fname, "wb");
    ctx->req.body.len = 0;
  }

  size_t bytes_to_write = MIN(conn->rbuf_size - conn->rbuf_read,
                              ctx->req.body.expected_len - ctx->req.body.len);
  size_t bytes_written = fwrite(&conn->rbuf[conn->rbuf_read], sizeof(uint8_t),
                                bytes_to_write, ctx->req.body.file);
  ctx->req.body.len += bytes_written;
  conn->rbuf_read += bytes_written;

  return ctx->req.body.len == ctx->req.body.expected_len;
}

bool http_loop_step_auth(event_loop_conn *conn) {
  http_loop_ctx *ctx = conn->ctx;

  for (size_t i = 0; i < ctx->req.num_headers; i++) {
    struct phr_header *header = &ctx->req.headers[i];

    if ((strncmp("X-Api-Key", header->name, header->name_len) == 0) &&
        (strncmp(header->value, ctx->g->api_key, header->value_len) == 0) &&
        (strlen(ctx->g->api_key) == header->value_len)) {
      return true;
    }
  }

  ctx->res.status = http_unauthorized;
  conn->state = event_loop_conn_state_res;

  return true;
}

bool http_loop_step_switch_res(event_loop_conn *conn) {
  conn->state = event_loop_conn_state_res;

  return true;
}