#define _POSIX_C_SOURCE 200809L

#include "eval.h"

#include "buffers.h"
#include "ccdjit.h"
#include "common.h"
#include "config.h"
#include "ecex.h"
#include "util.h"

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

static ecex_t *g_eval_editor = NULL;
static unsigned long g_eval_serial = 0;

typedef int (*ecex_eval_entry_fn)(int argc, char **argv);

static buffer_t *eval_output_buffer(ecex_t *ed) {
    if (!ed) return NULL;

    buffer_t *out = ecex_create_interactive_buffer(ed, "*eval-output*");
    if (out) {
        ecex_buffer_set_major_mode_by_name(ed, out, "eval-output-mode");
    }

    return out;
}

static void eval_append_diag(buffer_t *out, ccdjit_context *ctx) {
    if (!out || !ctx) return;

    const ccdjit_diagnostic *diag = ccdjit_context_last_error(ctx);
    if (!diag) {
        buffer_append(out, "ccdjit: unknown error\n");
        return;
    }

    char line[1024];
    snprintf(line,
             sizeof(line),
             "ccdjit error [%s] %s:%d:%d: %s\n",
             diag->phase ? diag->phase : "?",
             diag->filename ? diag->filename : "<input>",
             diag->line,
             diag->column,
             diag->message ? diag->message : "(no message)");
    buffer_append(out, line);

    if (diag->source_line) {
        buffer_append(out, diag->source_line);
        buffer_append(out, "\n");
    }

    if (diag->caret_line) {
        buffer_append(out, diag->caret_line);
        buffer_append(out, "\n");
    }
}

typedef struct eval_capture {
    FILE *file;
    int saved_stdout;
    int saved_stderr;
    int active;
} eval_capture_t;

static void eval_capture_init(eval_capture_t *capture) {
    if (!capture) return;

    capture->file = NULL;
    capture->saved_stdout = -1;
    capture->saved_stderr = -1;
    capture->active = 0;
}

static int eval_capture_begin(eval_capture_t *capture, buffer_t *out) {
    if (!capture) return ECEX_ERR;

    eval_capture_init(capture);

    capture->file = tmpfile();
    if (!capture->file) {
        if (out) buffer_append(out, "warning: failed to create stdout capture file\n");
        return ECEX_ERR;
    }

    int capture_fd = fileno(capture->file);
    if (capture_fd < 0) {
        if (out) buffer_append(out, "warning: failed to get stdout capture fd\n");
        fclose(capture->file);
        eval_capture_init(capture);
        return ECEX_ERR;
    }

    fflush(NULL);

    capture->saved_stdout = dup(STDOUT_FILENO);
    capture->saved_stderr = dup(STDERR_FILENO);

    if (capture->saved_stdout < 0 || capture->saved_stderr < 0) {
        if (out) buffer_append(out, "warning: failed to save stdout/stderr\n");

        if (capture->saved_stdout >= 0) close(capture->saved_stdout);
        if (capture->saved_stderr >= 0) close(capture->saved_stderr);
        fclose(capture->file);
        eval_capture_init(capture);
        return ECEX_ERR;
    }

    if (dup2(capture_fd, STDOUT_FILENO) < 0 ||
        dup2(capture_fd, STDERR_FILENO) < 0) {
        if (out) buffer_append(out, "warning: failed to redirect stdout/stderr\n");

        dup2(capture->saved_stdout, STDOUT_FILENO);
        dup2(capture->saved_stderr, STDERR_FILENO);
        close(capture->saved_stdout);
        close(capture->saved_stderr);
        fclose(capture->file);
        eval_capture_init(capture);
        return ECEX_ERR;
    }

    capture->active = 1;
    return ECEX_OK;
}

static void eval_capture_restore(eval_capture_t *capture) {
    if (!capture || !capture->active) return;

    fflush(NULL);

    if (capture->saved_stdout >= 0) {
        dup2(capture->saved_stdout, STDOUT_FILENO);
        close(capture->saved_stdout);
        capture->saved_stdout = -1;
    }

    if (capture->saved_stderr >= 0) {
        dup2(capture->saved_stderr, STDERR_FILENO);
        close(capture->saved_stderr);
        capture->saved_stderr = -1;
    }

    capture->active = 0;
}

static void eval_capture_append_output(eval_capture_t *capture, buffer_t *out) {
    if (!capture || !capture->file || !out) return;

    if (fseek(capture->file, 0, SEEK_END) != 0) {
        return;
    }

    long size = ftell(capture->file);
    if (size <= 0) {
        return;
    }

    if (fseek(capture->file, 0, SEEK_SET) != 0) {
        return;
    }

    buffer_append(out, "stdout/stderr:\n");

    char chunk[4096];
    size_t n = 0;

    while ((n = fread(chunk, 1, sizeof(chunk), capture->file)) > 0) {
        size_t old_len = out->len;

        if (buffer_reserve(out, out->len + n + 1) != ECEX_OK) {
            buffer_append(out, "\n[output truncated: allocation failed]\n");
            return;
        }

        memcpy(out->data + old_len, chunk, n);
        out->len += n;
        out->data[out->len] = '\0';
        out->point = out->len;
    }

    if (out->len > 0 && out->data[out->len - 1] != '\n') {
        buffer_append(out, "\n");
    }

    buffer_append(out, "\n");
}

static void eval_capture_finish(eval_capture_t *capture, buffer_t *out) {
    if (!capture) return;

    eval_capture_restore(capture);
    eval_capture_append_output(capture, out);

    if (capture->file) {
        fclose(capture->file);
    }

    eval_capture_init(capture);
}

static int source_has_main(const char *source) {
    if (!source) return 0;

    return strstr(source, "main(") != NULL ||
           strstr(source, "main (") != NULL;
}

static int eval_trace_enabled(void) {
    const char *log = getenv("ECEX_LOG");
    const char *trace_eval = getenv("ECEX_TRACE_EVAL");
    return (log && log[0] && log[0] != '0') ||
           (trace_eval && trace_eval[0] && trace_eval[0] != '0');
}

static size_t eval_source_line_count(const char *source, size_t source_len) {
    if (!source || source_len == 0) return 0;

    size_t lines = 1;
    for (size_t i = 0; i < source_len; i++) {
        if (source[i] == '\n' && i + 1 < source_len) lines++;
    }
    return lines;
}

static size_t eval_append_escaped_char(char *out, size_t len, size_t cap, unsigned char c) {
    static const char hex[] = "0123456789abcdef";
    if (!out || cap == 0 || len >= cap) return len;

    if (c == '\t') {
        for (int i = 0; i < 4 && len + 1 < cap; i++) out[len++] = ' ';
    } else if (c == '\\') {
        if (len + 2 < cap) {
            out[len++] = '\\';
            out[len++] = '\\';
        }
    } else if (c < 32 || c == 127) {
        if (len + 4 < cap) {
            out[len++] = '\\';
            out[len++] = 'x';
            out[len++] = hex[(c >> 4) & 0x0f];
            out[len++] = hex[c & 0x0f];
        }
    } else {
        if (len + 1 < cap) out[len++] = (char)c;
    }

    out[len < cap ? len : cap - 1] = '\0';
    return len;
}

static void eval_log_source_line(size_t line_no, const char *line, size_t line_len) {
    size_t pos = 0;
    int continued = 0;

    if (line_len == 0) {
        ecex_logf("%4lu |", (unsigned long)line_no);
        return;
    }

    while (pos < line_len) {
        char out[1024];
        size_t len = 0;
        int prefix_len = snprintf(out,
                                  sizeof(out),
                                  "%4lu %c ",
                                  (unsigned long)line_no,
                                  continued ? '>' : '|');
        if (prefix_len < 0) return;
        if ((size_t)prefix_len >= sizeof(out)) prefix_len = (int)sizeof(out) - 1;
        len = (size_t)prefix_len;

        size_t before = pos;
        while (pos < line_len && len + 8 < sizeof(out)) {
            len = eval_append_escaped_char(out, len, sizeof(out), (unsigned char)line[pos]);
            pos++;
        }

        if (pos == before) {
            len = eval_append_escaped_char(out, len, sizeof(out), (unsigned char)line[pos]);
            pos++;
        }

        ecex_log(out);
        continued = 1;
    }
}

static void eval_log_source(const char *source,
                            const char *filename,
                            int wrap_source,
                            unsigned long serial) {
    if (!source || !eval_trace_enabled()) return;

    size_t source_len = strlen(source);
    size_t line_count = eval_source_line_count(source, source_len);
    char header[768];
    snprintf(header,
             sizeof(header),
             "eval source start serial=%lu file=%s mode=%s bytes=%lu lines=%lu",
             serial,
             filename ? filename : "<eval>",
             wrap_source ? "wrapped-statements" : "translation-unit",
             (unsigned long)source_len,
             (unsigned long)line_count);

    ecex_log_group_begin(header);

    if (source_len == 0) {
        ecex_log("(empty)");
    } else {
        size_t line_start = 0;
        size_t line_no = 1;
        for (size_t i = 0; i <= source_len; i++) {
            if (source[i] != '\n' && source[i] != '\0') continue;
            if (source[i] == '\0' && line_start == source_len && source_len > 0 && source[source_len - 1] == '\n') {
                break;
            }

            size_t line_len = i - line_start;
            if (line_len > 0 && source[line_start + line_len - 1] == '\r') line_len--;
            eval_log_source_line(line_no, source + line_start, line_len);

            if (source[i] == '\0') break;
            line_start = i + 1;
            line_no++;
        }
    }

    ecex_log_group_end("eval source end");
}

static char *make_eval_source(const char *source, int wrap_as_statements, unsigned long serial) {
    if (!source) return NULL;

    /* Keep eval-defined command/helper symbols private.  Successful eval
     * modules stay loaded, and default-visible ELF symbols can otherwise be
     * interposed by the first eval that defined the same names. */
    char prefix[512];
    int prefix_len = snprintf(prefix,
        sizeof(prefix),
        "#include \"ecex.h\"\n"
        "#include \"buffers.h\"\n"
        "extern ecex_t *__ecex_eval_editor;\n"
        "#define ECEX_ED (__ecex_eval_editor)\n"
        "#define main __ecex_eval_user_main_%lu\n"
        "#pragma GCC visibility push(hidden)\n"
        "\n",
        serial);
    if (prefix_len < 0 || (size_t)prefix_len >= sizeof(prefix)) return NULL;

    const char *wrapper_open =
        "int main(int argc, char **argv) {\n"
        "    (void)argc;\n"
        "    (void)argv;\n"
        "    ecex_t *ed = __ecex_eval_editor;\n"
        "    (void)ed;\n";

    const char *wrapper_close =
        "\n"
        "    return 0;\n"
        "}\n";

    int do_wrap = wrap_as_statements || !source_has_main(source);

    size_t source_len = strlen(source);
    size_t open_len = do_wrap ? strlen(wrapper_open) : 0;
    size_t close_len = do_wrap ? strlen(wrapper_close) : 0;
    char entry_wrapper[384];
    int entry_wrapper_len = 0;
    const char *suffix =
        "\n"
        "#pragma GCC visibility pop\n"
        "#undef main\n";

    entry_wrapper_len = snprintf(entry_wrapper,
                                  sizeof(entry_wrapper),
                                  "int ecex_eval_entry(int argc, char **argv) {\n"
                                  "    return ((int (*)(int, char **))__ecex_eval_user_main_%lu)(argc, argv);\n"
                                  "}\n"
                                  "int main(int argc, char **argv) {\n"
                                  "    return ecex_eval_entry(argc, argv);\n"
                                  "}\n",
                                  serial);
    if (entry_wrapper_len < 0 || (size_t)entry_wrapper_len >= sizeof(entry_wrapper)) return NULL;

    size_t suffix_len = strlen(suffix);

    char *combined = malloc((size_t)prefix_len + open_len + source_len + close_len +
                            suffix_len + (size_t)entry_wrapper_len + 2);
    if (!combined) return NULL;

    char *p = combined;
    memcpy(p, prefix, (size_t)prefix_len);
    p += prefix_len;

    if (do_wrap) {
        memcpy(p, wrapper_open, open_len);
        p += open_len;
    }

    memcpy(p, source, source_len);
    p += source_len;

    if (do_wrap) {
        if (source_len == 0 || source[source_len - 1] != '\n') {
            *p++ = '\n';
        }
        memcpy(p, wrapper_close, close_len);
        p += close_len;
    }

    memcpy(p, suffix, suffix_len);
    p += suffix_len;

    memcpy(p, entry_wrapper, (size_t)entry_wrapper_len);
    p += entry_wrapper_len;

    *p = '\0';
    return combined;
}

static int remember_last_eval(ecex_t *ed,
                              const char *source,
                              const char *filename,
                              int wrap_as_statements) {
    if (!ed || !source) return ECEX_ERR;

    char *source_copy = ecex_strdup(source);
    char *filename_copy = ecex_strdup(filename ? filename : "<eval>");
    if (!source_copy || !filename_copy) {
        free(source_copy);
        free(filename_copy);
        return ECEX_ERR;
    }

    free(ed->last_eval_source);
    free(ed->last_eval_filename);
    ed->last_eval_source = source_copy;
    ed->last_eval_filename = filename_copy;
    ed->last_eval_wrap_as_statements = wrap_as_statements;
    return ECEX_OK;
}

int ecex_eval_source(ecex_t *ed,
                     const char *source,
                     const char *filename,
                     int wrap_as_statements) {
    if (!ed || !source) return ECEX_ERR;

    remember_last_eval(ed, source, filename, wrap_as_statements);

    buffer_t *out = eval_output_buffer(ed);
    if (!out) return ECEX_ERR;

    buffer_clear(out);
    buffer_set_interactive(out, 1);
    ecex_buffer_set_major_mode_by_name(ed, out, "eval-output-mode");
    buffer_append(out, "Eval output (g: re-eval, q: quit window, ENTER: follow line if available)\n");
    buffer_append(out, "-------------------------------------------------------------------------\n\n");
    buffer_append(out, "Eval: ");
    buffer_append(out, filename ? filename : "<eval>");
    buffer_append(out, "\n\n");

    unsigned long eval_serial = ++g_eval_serial;
    int wrap_source = wrap_as_statements || !source_has_main(source);
    eval_log_source(source, filename, wrap_source, eval_serial);

    char *eval_source = make_eval_source(source, wrap_as_statements, eval_serial);
    if (!eval_source) {
        buffer_append(out, "failed to allocate eval source\n");
        ecex_switch_buffer(ed, "*eval-output*");
        return ECEX_ERR;
    }

    ccdjit_context *ctx = ccdjit_context_new(NULL);
    if (!ctx) {
        buffer_append(out, "failed to create ccdjit context\n");
        free(eval_source);
        ecex_switch_buffer(ed, "*eval-output*");
        return ECEX_ERR;
    }

    if (ecex_add_ccdjit_include_paths(ctx) != ECEX_OK ||
        ecex_register_host_symbols(ctx) != ECEX_OK ||
        ccdjit_context_register_symbol(ctx,
                                       "__ecex_eval_editor",
                                       (void *)&g_eval_editor) != 0) {
        buffer_append(out, "failed to prepare eval context\n");
        eval_append_diag(out, ctx);
        ccdjit_context_free(ctx);
        free(eval_source);
        ecex_switch_buffer(ed, "*eval-output*");
        return ECEX_ERR;
    }

    g_eval_editor = ed;

    ccdjit_module *module = NULL;
    if (ccdjit_compile_string(ctx,
                              eval_source,
                              filename ? filename : "<eval>",
                              &module) != 0) {
        buffer_append(out, "compile failed\n\n");
        eval_append_diag(out, ctx);
        g_eval_editor = NULL;
        ccdjit_context_free(ctx);
        free(eval_source);
        ecex_switch_buffer(ed, "*eval-output*");
        return ECEX_ERR;
    }

    char entry_name[128];
    snprintf(entry_name, sizeof(entry_name), "ecex_eval_entry");
    ecex_eval_entry_fn entry = (ecex_eval_entry_fn)ccdjit_module_symbol(module, entry_name);
    if (!entry) {
        buffer_append(out, "failed to resolve eval entry: ");
        buffer_append(out, entry_name);
        buffer_append(out, "\n");
        ccdjit_module_free(module);
        g_eval_editor = NULL;
        ccdjit_context_free(ctx);
        free(eval_source);
        ecex_switch_buffer(ed, "*eval-output*");
        return ECEX_ERR;
    }

    int result = 0;
    eval_capture_t capture;
    int capture_enabled = (eval_capture_begin(&capture, out) == ECEX_OK);
    int runtime_status = 0;
    result = entry(0, NULL);

    if (capture_enabled) {
        eval_capture_finish(&capture, out);
    }

    /*
     * Eval code can mutate public editor fields directly, bypassing the
     * setter functions that normally bump UI revisions. Treat a completed
     * eval as a possible UI mutation so the app layer always gets a repaint
     * opportunity.
     */
    ed->ui_revision++;

    if (eval_trace_enabled()) {
        ecex_logf("eval result serial=%lu entry=%p result=%d font_size=%.3f font_revision=%lu ui_revision=%lu",
                  eval_serial,
                  (void *)entry,
                  result,
                  (double)ecex_get_font_size(ed),
                  ed->font_revision,
                  ed->ui_revision);
    }

    if (runtime_status != 0) {
        buffer_append(out, "runtime failed\n\n");
        eval_append_diag(out, ctx);
        ccdjit_module_free(module);
        g_eval_editor = NULL;
        ccdjit_context_free(ctx);
        free(eval_source);
        ecex_switch_buffer(ed, "*eval-output*");
        return ECEX_ERR;
    }

    char line[128];
    snprintf(line, sizeof(line), "ok, result = %d\n", result);
    buffer_append(out, line);

    /*
     * Keep successful eval modules alive.  This makes eval useful for live
     * customization: code evaluated from a buffer may register commands whose
     * function pointers remain valid after eval returns.
     */
    if (ecex_keep_jit_module(ed, module) != ECEX_OK) {
        buffer_append(out, "failed to keep eval module alive\n");
        ccdjit_module_free(module);
        g_eval_editor = NULL;
        ccdjit_context_free(ctx);
        free(eval_source);
        ecex_switch_buffer(ed, "*eval-output*");
        return ECEX_ERR;
    }

    g_eval_editor = NULL;
    ccdjit_context_free(ctx);
    free(eval_source);

    out->modified = 0;
    out->point = 0;
    ecex_switch_buffer(ed, "*eval-output*");
    return ECEX_OK;
}

int ecex_eval_current_buffer(ecex_t *ed) {
    buffer_t *buf = ecex_current_buffer(ed);
    if (!buf || !buf->data) return ECEX_ERR;

    return ecex_eval_source(ed,
                            buf->data,
                            buf->path ? buf->path : buf->name,
                            0);
}

int ecex_eval_current_line(ecex_t *ed) {
    buffer_t *buf = ecex_current_buffer(ed);
    if (!buf) return ECEX_ERR;

    char *line = buffer_current_line_copy(buf);
    if (!line) return ECEX_ERR;

    int result = ecex_eval_source(ed, line, "<current-line>", 1);
    free(line);
    return result;
}


int ecex_eval_current_region(ecex_t *ed) {
    buffer_t *buf = ecex_current_buffer(ed);
    if (!buf || !buffer_has_selection(buf)) return ECEX_ERR;

    size_t start = 0;
    size_t end = 0;
    buffer_selection_range(buf, &start, &end);

    char *region = buffer_substring(buf, start, end);
    if (!region) return ECEX_ERR;

    int result = ecex_eval_source(ed, region, "<region>", 1);
    free(region);
    return result;
}

int ecex_eval_file(ecex_t *ed, const char *path) {
    if (!ed || !path || !path[0]) return ECEX_ERR;

    size_t size = 0;
    char *source = ecex_read_entire_file(path, &size);
    (void)size;

    if (!source) {
        buffer_t *out = eval_output_buffer(ed);
        if (out) {
            buffer_clear(out);
            buffer_append(out, "failed to read eval file: ");
            buffer_append(out, path);
            buffer_append(out, "\n");
            out->modified = 0;
            ecex_switch_buffer(ed, "*eval-output*");
        }
        return ECEX_ERR;
    }

    int result = ecex_eval_source(ed, source, path, 0);
    free(source);
    return result;
}

int ecex_eval_rerun_last(ecex_t *ed) {
    if (!ed || !ed->last_eval_source) return ECEX_ERR;

    char *source = ecex_strdup(ed->last_eval_source);
    char *filename = ecex_strdup(ed->last_eval_filename ? ed->last_eval_filename : "<eval>");
    int wrap = ed->last_eval_wrap_as_statements;

    if (!source || !filename) {
        free(source);
        free(filename);
        return ECEX_ERR;
    }

    int result = ecex_eval_source(ed, source, filename, wrap);
    free(source);
    free(filename);
    return result;
}