#include <stdio.h>
#include <string.h>

#include "php.h"
#include "zend_extensions.h"

#define MINI_XDEBUG_CMD_END -1
#define MINI_XDEBUG_CMD_INVALID 0
#define MINI_XDEBUG_CMD_NEXT 1

static int g_is_first_statement;
static int g_do_next_cmd;
static int g_next_call_depth;

static void mini_xdebug_activate(void) {
    CG(compiler_options) |= ZEND_COMPILE_EXTENDED_STMT;
    g_is_first_statement = 1;
    g_do_next_cmd = 0;
    g_next_call_depth = 0;
}

static int get_call_depth(void) {
    int depth = 0;
    zend_execute_data* ex = EG(current_execute_data);
    while (ex) {
        depth++;
        ex = ex->prev_execute_data;
    }
    return depth;
}

static void show_context(const char* filename, int lineno) {
    FILE* fp = fopen(filename, "r");
    if (!fp) {
        return;
    }

    char buf[1024];
    int n = 0;
    while (fgets(buf, sizeof(buf), fp)) {
        n++;
        if (lineno - 1 <= n && n <= lineno + 1) {
            fprintf(stdout, "%s %3d | %s", n == lineno ? ">" : " ", n, buf);
        }
        if (n > lineno + 1) {
            break;
        }
    }
    fclose(fp);
}

static void show_prompt(void) {
    fprintf(stdout, "(mini-xdebug) ");
    fflush(stdout);
}

static int query_command(char* buf) {
    if (!fgets(buf, sizeof(buf), stdin)) {
        return MINI_XDEBUG_CMD_END;
    }
    buf[strcspn(buf, "\n")] = '\0';

    return (!strcmp(buf, "next") || !strcmp(buf, "n"))
               ? MINI_XDEBUG_CMD_NEXT
               : MINI_XDEBUG_CMD_INVALID;
}

static void mini_xdebug_statement_handler(zend_execute_data* frame) {
    if (!g_is_first_statement && !g_do_next_cmd) {
        return;
    }

    uint32_t lineno = EG(current_execute_data)->opline->lineno;
    const char* filename = ZSTR_VAL(frame->func->op_array.filename);
    int depth = get_call_depth();

    if (g_is_first_statement) {
        g_is_first_statement = 0;
    } else if (g_do_next_cmd) {
        if (depth > g_next_call_depth) {
            return;
        }
        g_do_next_cmd = 0;
    }

    fprintf(stdout, "\n%s:%d\n", filename, lineno);
    show_context(filename, lineno);

    char command_buf[256];
    for (;;) {
        show_prompt();
        int cmd = query_command(command_buf);
        if (cmd == MINI_XDEBUG_CMD_NEXT) {
            g_do_next_cmd = 1;
            g_next_call_depth = depth;
            break;
        } else if (cmd == MINI_XDEBUG_CMD_END) {
            break;
        } else {
            fprintf(stdout, "Available commands: next (n)\n");
        }
    }
}

#ifndef ZEND_EXT_API
#define ZEND_EXT_API ZEND_DLEXPORT
#endif

ZEND_EXT_API zend_extension_version_info extension_version_info = {
    ZEND_EXTENSION_API_NO,
    (char*)ZEND_EXTENSION_BUILD_ID,
};

ZEND_DLEXPORT zend_extension zend_extension_entry = {
    "mini-xdebug",                 /* name */
    "0.1.0",                       /* version */
    "nsfisis",                     /* author */
    "",                            /* URL */
    "",                            /* copyright */
    NULL,                          /* startup */
    NULL,                          /* shutdown */
    mini_xdebug_activate,          /* activate */
    NULL,                          /* deactivate */
    NULL,                          /* message_handler */
    NULL,                          /* op_array_handler */
    mini_xdebug_statement_handler, /* statement_handler */
    NULL,                          /* fcall_begin_handler */
    NULL,                          /* fcall_end_handler */
    NULL,                          /* op_array_ctor */
    NULL,                          /* op_array_dtor */
    STANDARD_ZEND_EXTENSION_PROPERTIES,
};