// Written by retoor@molodetz.nl
// Improved version with better reliability and chunked content support

// MIT License

#ifndef R_HTTP_H
#define R_HTTP_H

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <openssl/ssl.h>
#include <openssl/err.h>
#include <json-c/json.h>
#include <stdbool.h>
#include "url.h"

#define INITIAL_BUFFER_SIZE (1024 * 1024)
#define MAX_HEADER_SIZE (8 * 1024)

void init_openssl() {
    SSL_load_error_strings();
    OpenSSL_add_ssl_algorithms();
}

void cleanup_openssl() {
    EVP_cleanup();
}

SSL_CTX *create_context() {
    const SSL_METHOD *method = TLS_client_method();
    SSL_CTX *ctx = SSL_CTX_new(method);
    if (!ctx) {
        perror("Unable to create SSL context");
        ERR_print_errors_fp(stderr);
        return NULL;
    }
    SSL_CTX_set_verify(ctx, SSL_VERIFY_NONE, NULL);
    SSL_CTX_load_verify_locations(ctx, "/etc/ssl/certs/ca-certificates.crt", NULL);
    return ctx;
}

int create_socket(const char *hostname, int port) {
    struct hostent *host;
    struct sockaddr_in addr;

    host = gethostbyname(hostname);
    if (!host) {
        perror("Unable to resolve host");
        return -1;
    }

    int sock = socket(AF_INET, SOCK_STREAM, 0);
    if (sock < 0) {
        perror("Unable to create socket");
        return -1;
    }

    addr.sin_family = AF_INET;
    addr.sin_port = htons(port);
    addr.sin_addr.s_addr = *(long *)(host->h_addr);

    if (connect(sock, (struct sockaddr *)&addr, sizeof(addr)) != 0) {
        perror("Unable to connect to host");
        close(sock);
        return -1;
    }

    return sock;
}

char *read_until_ssl(SSL *ssl, const char *until, size_t max_size) {
    char *data = (char *)malloc(max_size);
    if (!data) return NULL;
    
    size_t index = 0;
    size_t until_len = strlen(until);
    
    while (index < max_size - 1) {
        char c;
        int bytes = SSL_read(ssl, &c, 1);
        if (bytes <= 0) {
            free(data);
            return NULL;
        }
        
        data[index++] = c;
        data[index] = '\0';
        
        if (index >= until_len && 
            memcmp(data + index - until_len, until, until_len) == 0) {
            return data;
        }
    }
    
    free(data);
    return NULL;
}

char *read_until(int sock, const char *until, size_t max_size) {
    char *data = (char *)malloc(max_size);
    if (!data) return NULL;
    
    size_t index = 0;
    size_t until_len = strlen(until);
    
    while (index < max_size - 1) {
        char c;
        ssize_t bytes = recv(sock, &c, 1, 0);
        if (bytes <= 0) {
            free(data);
            return NULL;
        }
        
        data[index++] = c;
        data[index] = '\0';
        
        if (index >= until_len && 
            memcmp(data + index - until_len, until, until_len) == 0) {
            return data;
        }
    }
    
    free(data);
    return NULL;
}

size_t hex_to_int(const char *hex) {
    size_t result = 0;
    while (*hex && *hex != '\r' && *hex != '\n') {
        char c = *hex++;
        if (c >= '0' && c <= '9') {
            result = result * 16 + (c - '0');
        } else if (c >= 'a' && c <= 'f') {
            result = result * 16 + (c - 'a' + 10);
        } else if (c >= 'A' && c <= 'F') {
            result = result * 16 + (c - 'A' + 10);
        }
    }
    return result;
}

bool http_has_header(const char *http_headers, const char *http_header_name) {
    char search_for[strlen(http_header_name) + 3];
    snprintf(search_for, sizeof(search_for), "%s: ", http_header_name);
    return strstr(http_headers, search_for) != NULL;
}

char *http_header_get_str(const char *http_headers, const char *http_header_name) {
    char search_for[strlen(http_header_name) + 3];
    snprintf(search_for, sizeof(search_for), "%s: ", http_header_name);
    
    const char *header = strstr(http_headers, search_for);
    if (!header) return NULL;
    
    header += strlen(search_for);
    const char *end = strstr(header, "\r\n");
    if (!end) return NULL;
    
    size_t value_len = end - header;
    char *result = (char *)malloc(value_len + 1);
    if (!result) return NULL;
    
    memcpy(result, header, value_len);
    result[value_len] = '\0';
    return result;
}

long http_header_get_long(const char *http_headers, const char *http_header_name) {
    char *str_value = http_header_get_str(http_headers, http_header_name);
    if (!str_value) return 0;
    
    long long_value = atol(str_value);
    free(str_value);
    return long_value;
}

static char *read_chunked_body_ssl(SSL *ssl) {
    size_t total_size = 0;
    size_t buffer_capacity = INITIAL_BUFFER_SIZE;
    char *buffer = (char *)malloc(buffer_capacity);
    if (!buffer) return NULL;
    
    while (1) {
        // Read chunk size line
        char *chunk_header = read_until_ssl(ssl, "\r\n", 256);
        if (!chunk_header) {
            free(buffer);
            return NULL;
        }
        
        size_t chunk_size = hex_to_int(chunk_header);
        free(chunk_header);
        
        if (chunk_size == 0) {
            // Read trailing \r\n after last chunk
            char trailing[3];
            SSL_read(ssl, trailing, 2);
            break;
        }
        
        // Resize buffer if needed
        if (total_size + chunk_size + 1 > buffer_capacity) {
            buffer_capacity = total_size + chunk_size + INITIAL_BUFFER_SIZE;
            char *new_buffer = (char *)realloc(buffer, buffer_capacity);
            if (!new_buffer) {
                free(buffer);
                return NULL;
            }
            buffer = new_buffer;
        }
        
        // Read chunk data
        size_t bytes_read = 0;
        while (bytes_read < chunk_size) {
            int n = SSL_read(ssl, buffer + total_size + bytes_read, 
                           chunk_size - bytes_read);
            if (n <= 0) {
                free(buffer);
                return NULL;
            }
            bytes_read += n;
        }
        
        total_size += chunk_size;
        
        // Read trailing \r\n after chunk data
        char trailing[3];
        SSL_read(ssl, trailing, 2);
    }
    
    buffer[total_size] = '\0';
    return buffer;
}

static char *read_chunked_body(int sock) {
    size_t total_size = 0;
    size_t buffer_capacity = INITIAL_BUFFER_SIZE;
    char *buffer = (char *)malloc(buffer_capacity);
    if (!buffer) return NULL;
    
    while (1) {
        // Read chunk size line
        char *chunk_header = read_until(sock, "\r\n", 256);
        if (!chunk_header) {
            free(buffer);
            return NULL;
        }
        
        size_t chunk_size = hex_to_int(chunk_header);
        free(chunk_header);
        
        if (chunk_size == 0) {
            // Read trailing \r\n after last chunk
            char trailing[3];
            recv(sock, trailing, 2, 0);
            break;
        }
        
        // Resize buffer if needed
        if (total_size + chunk_size + 1 > buffer_capacity) {
            buffer_capacity = total_size + chunk_size + INITIAL_BUFFER_SIZE;
            char *new_buffer = (char *)realloc(buffer, buffer_capacity);
            if (!new_buffer) {
                free(buffer);
                return NULL;
            }
            buffer = new_buffer;
        }
        
        // Read chunk data
        size_t bytes_read = 0;
        while (bytes_read < chunk_size) {
            ssize_t n = recv(sock, buffer + total_size + bytes_read, 
                           chunk_size - bytes_read, 0);
            if (n <= 0) {
                free(buffer);
                return NULL;
            }
            bytes_read += n;
        }
        
        total_size += chunk_size;
        
        // Read trailing \r\n after chunk data
        char trailing[3];
        recv(sock, trailing, 2, 0);
    }
    
    buffer[total_size] = '\0';
    return buffer;
}

char *https_post(char *url, char *data) {
    url_t parsed_url;
    parse_url(url, &parsed_url);
    
    init_openssl();
    SSL_CTX *ctx = create_context();
    if (!ctx) return NULL;
    
    int sock = create_socket(parsed_url.hostname, 443);
    if (sock < 0) {
        SSL_CTX_free(ctx);
        cleanup_openssl();
        return NULL;
    }
    
    SSL *ssl = SSL_new(ctx);
    SSL_set_connect_state(ssl);
    SSL_set_tlsext_host_name(ssl, parsed_url.hostname);
    SSL_set_fd(ssl, sock);
    
    char *result = NULL;
    
    if (SSL_connect(ssl) <= 0) {
        ERR_print_errors_fp(stderr);
    } else {
        size_t data_len = strlen(data);
        size_t request_size = data_len + 1024;
        char *request = (char *)malloc(request_size);
        
        snprintf(request, request_size,
                "POST %s HTTP/1.1\r\n"
                "Host: %s\r\n"
                "Content-Length: %zu\r\n"
                "Content-Type: application/json\r\n"
                "Connection: close\r\n"
                "\r\n"
                "%s",
                parsed_url.path, parsed_url.hostname, data_len, 
                 data);
        
        SSL_write(ssl, request, strlen(request));
        free(request);
        
        char *headers = read_until_ssl(ssl, "\r\n\r\n", MAX_HEADER_SIZE);
        if (headers) {
            long content_length = http_header_get_long(headers, "Content-Length");
            
            if (content_length > 0) {
                result = (char *)malloc(content_length + 1);
                if (result) {
                    size_t bytes_read = 0;
                    while (bytes_read < (size_t)content_length) {
                        int n = SSL_read(ssl, result + bytes_read, 
                                       content_length - bytes_read);
                        if (n <= 0) {
                            free(result);
                            result = NULL;
                            break;
                        }
                        bytes_read += n;
                    }
                    if (result) {
                        result[content_length] = '\0';
                    }
                }
            } else if (http_has_header(headers, "Transfer-Encoding")) {
                result = read_chunked_body_ssl(ssl);
            }
            
            free(headers);
        }
    }
    
    SSL_free(ssl);
    close(sock);
    SSL_CTX_free(ctx);
    cleanup_openssl();
    
    return result;
}

char *https_get(char *url) {
    url_t parsed_url;
    parse_url(url, &parsed_url);
    
    init_openssl();
    SSL_CTX *ctx = create_context();
    if (!ctx) return NULL;
    
    int sock = create_socket(parsed_url.hostname, 443);
    if (sock < 0) {
        SSL_CTX_free(ctx);
        cleanup_openssl();
        return NULL;
    }
    
    SSL *ssl = SSL_new(ctx);
    SSL_set_connect_state(ssl);
    SSL_set_tlsext_host_name(ssl, parsed_url.hostname);
    SSL_set_fd(ssl, sock);
    
    char *result = NULL;
    
    if (SSL_connect(ssl) <= 0) {
        ERR_print_errors_fp(stderr);
    } else {
        char request[2048];
        snprintf(request, sizeof(request),
                "GET %s HTTP/1.1\r\n"
                "Host: %s\r\n"
                "Connection: close\r\n"
                "\r\n",
                parsed_url.path, parsed_url.hostname);
        
        SSL_write(ssl, request, strlen(request));
        
        char *headers = read_until_ssl(ssl, "\r\n\r\n", MAX_HEADER_SIZE);
        if (headers) {
            long content_length = http_header_get_long(headers, "Content-Length");
            
            if (content_length > 0) {
                result = (char *)malloc(content_length + 1);
                if (result) {
                    size_t bytes_read = 0;
                    while (bytes_read < (size_t)content_length) {
                        int n = SSL_read(ssl, result + bytes_read, 
                                       content_length - bytes_read);
                        if (n <= 0) {
                            free(result);
                            result = NULL;
                            break;
                        }
                        bytes_read += n;
                    }
                    if (result) {
                        result[content_length] = '\0';
                    }
                }
            } else if (http_has_header(headers, "Transfer-Encoding")) {
                result = read_chunked_body_ssl(ssl);
            }
            
            free(headers);
        }
    }
    
    SSL_free(ssl);
    close(sock);
    SSL_CTX_free(ctx);
    cleanup_openssl();
    
    return result;
}

char *http_post(char *url, char *data) {
    url_t parsed_url;
    parse_url(url, &parsed_url);
    
    int port = parsed_url.port ? atoi(parsed_url.port) : 80;
    int sock = create_socket(parsed_url.hostname, port);
    if (sock < 0) return NULL;
    
    char *result = NULL;
    size_t data_len = strlen(data);
    size_t request_size = data_len + 1024;
    char *request = (char *)malloc(request_size);
    
    snprintf(request, request_size,
            "POST %s HTTP/1.1\r\n"
            "Host: %s\r\n"
            "Content-Length: %zu\r\n"
            "Content-Type: application/json\r\n"
            "Connection: close\r\n"
            "\r\n"
            "%s",
            parsed_url.path, parsed_url.hostname, data_len, 
             data);
    
    send(sock, request, strlen(request), 0);
    free(request);
    
    char *headers = read_until(sock, "\r\n\r\n", MAX_HEADER_SIZE);
    if (headers) {
        long content_length = http_header_get_long(headers, "Content-Length");
        
        if (content_length > 0) {
            result = (char *)malloc(content_length + 1);
            if (result) {
                size_t bytes_read = 0;
                while (bytes_read < (size_t)content_length) {
                    ssize_t n = recv(sock, result + bytes_read, 
                                   content_length - bytes_read, 0);
                    if (n <= 0) {
                        free(result);
                        result = NULL;
                        break;
                    }
                    bytes_read += n;
                }
                if (result) {
                    result[content_length] = '\0';
                }
            }
        } else if (http_has_header(headers, "Transfer-Encoding")) {
            result = read_chunked_body(sock);
        }
        
        free(headers);
    }
    
    close(sock);
    return result;
}

char *http_get(char *url) {
    url_t parsed_url;
    parse_url(url, &parsed_url);
    
    int port = parsed_url.port ? atoi(parsed_url.port) : 80;
    int sock = create_socket(parsed_url.hostname, port);
    if (sock < 0) return NULL;
    
    char *result = NULL;
    char request[2048];
    
    snprintf(request, sizeof(request),
            "GET %s HTTP/1.1\r\n"
            "Host: %s\r\n"
            "Connection: close\r\n"
            "\r\n",
            parsed_url.path, parsed_url.hostname);
    
    send(sock, request, strlen(request), 0);
    
    char *headers = read_until(sock, "\r\n\r\n", MAX_HEADER_SIZE);
    if (headers) {
        long content_length = http_header_get_long(headers, "Content-Length");
        
        if (content_length > 0) {
            result = (char *)malloc(content_length + 1);
            if (result) {
                size_t bytes_read = 0;
                while (bytes_read < (size_t)content_length) {
                    ssize_t n = recv(sock, result + bytes_read, 
                                   content_length - bytes_read, 0);
                    if (n <= 0) {
                        free(result);
                        result = NULL;
                        break;
                    }
                    bytes_read += n;
                }
                if (result) {
                    result[content_length] = '\0';
                }
            }
        } else if (http_has_header(headers, "Transfer-Encoding")) {
            result = read_chunked_body(sock);
        }
        
        free(headers);
    }
    
    close(sock);
    return result;
}

#endif