#include "ecex.h"

#include <string.h>

#define C_MODE_PLUGIN_ID "c-mode"
#define C_MODE_LSP_PROVIDER_NAME "c-mode-clangd"
#define C_MODE_SLOT_CLANGD "clangd"

static int c_mode_line_starts_with(buffer_t *buffer, size_t first, size_t line_end, const char *word) {
    size_t len = strlen(word);
    if (!buffer || !word || first + len > line_end) return 0;
    if (strncmp(buffer->data + first, word, len) != 0) return 0;
    if (first + len == line_end) return 1;
    char c = buffer->data[first + len];
    return !(c == '_' ||
             (c >= 'a' && c <= 'z') ||
             (c >= 'A' && c <= 'Z') ||
             (c >= '0' && c <= '9'));
}

static int c_mode_line_ends_with_colon(buffer_t *buffer, size_t first, size_t line_end) {
    if (!buffer || first >= line_end) return 0;
    size_t p = line_end;
    while (p > first && (buffer->data[p - 1] == ' ' || buffer->data[p - 1] == '\t')) p--;
    return p > first && buffer->data[p - 1] == ':';
}

static size_t c_mode_previous_nonblank_line(buffer_t *buffer, size_t line_start) {
    if (!buffer || line_start == 0) return (size_t)-1;

    size_t end = line_start - 1;
    while (end > 0 && buffer->data[end - 1] == '\n') end--;

    for (;;) {
        size_t start = buffer_line_start_at(buffer, end);
        size_t line_end = buffer_line_end_at(buffer, start);
        size_t p = start;
        while (p < line_end && (buffer->data[p] == ' ' || buffer->data[p] == '\t')) p++;
        if (p < line_end) return start;
        if (start == 0) break;
        end = start - 1;
    }

    return (size_t)-1;
}

static int c_mode_brace_depth_before(buffer_t *buffer, size_t limit) {
    int depth = 0;
    int in_block = 0;
    int in_line = 0;
    int in_string = 0;
    int in_char = 0;
    int escaped = 0;

    if (!buffer || !buffer->data) return 0;
    if (limit > buffer->len) limit = buffer->len;

    for (size_t i = 0; i < limit; i++) {
        char c = buffer->data[i];
        char next = i + 1 < limit ? buffer->data[i + 1] : '\0';

        if (in_line) {
            if (c == '\n') in_line = 0;
            continue;
        }

        if (in_block) {
            if (c == '*' && next == '/') {
                in_block = 0;
                i++;
            }
            continue;
        }

        if (in_string) {
            if (escaped) escaped = 0;
            else if (c == '\\') escaped = 1;
            else if (c == '"') in_string = 0;
            else if (c == '\n') in_string = 0;
            continue;
        }

        if (in_char) {
            if (escaped) escaped = 0;
            else if (c == '\\') escaped = 1;
            else if (c == '\'') in_char = 0;
            else if (c == '\n') in_char = 0;
            continue;
        }

        if (c == '/' && next == '/') {
            in_line = 1;
            i++;
        } else if (c == '/' && next == '*') {
            in_block = 1;
            i++;
        } else if (c == '"') {
            in_string = 1;
        } else if (c == '\'') {
            in_char = 1;
        } else if (c == '{') {
            depth++;
        } else if (c == '}') {
            if (depth > 0) depth--;
        }
    }

    return depth;
}

static int cmd_c_indent_line(ecex_t *ed) {
    if (!ed) return -1;
    buffer_t *buffer = ecex_current_buffer(ed);
    if (!buffer || buffer->read_only || buffer_is_interactive(buffer)) return -1;

    size_t line_start = buffer_current_line_start(buffer);
    size_t line_end = buffer_current_line_end(buffer);
    size_t first = line_start;
    while (first < line_end && (buffer->data[first] == ' ' || buffer->data[first] == '\t')) first++;

    if (first < line_end && buffer->data[first] == '#') return ecex_indent_line_to(buffer, 0);

    int depth = c_mode_brace_depth_before(buffer, line_start);
    int target = depth * 4;

    if (first < line_end && buffer->data[first] == '}') target -= 4;

    size_t prev = c_mode_previous_nonblank_line(buffer, line_start);
    if (prev != (size_t)-1) {
        size_t prev_end = buffer_line_end_at(buffer, prev);
        size_t prev_first = prev;
        while (prev_first < prev_end && (buffer->data[prev_first] == ' ' || buffer->data[prev_first] == '\t')) prev_first++;

        if ((c_mode_line_starts_with(buffer, prev_first, prev_end, "case") ||
             c_mode_line_starts_with(buffer, prev_first, prev_end, "default")) &&
            c_mode_line_ends_with_colon(buffer, prev_first, prev_end) &&
            !(c_mode_line_starts_with(buffer, first, line_end, "case") ||
              c_mode_line_starts_with(buffer, first, line_end, "default") ||
              (first < line_end && buffer->data[first] == '}'))) {
            target += 4;
        }
    }

    if (target < 0) target = 0;
    return ecex_indent_line_to(buffer, target);
}

static int cmd_c_complete(ecex_t *ed) {
    return ecex_complete_at_point(ed);
}

static int c_mode_file_handler(ecex_t *ed, buffer_t *buffer) {
    if (!ed || !buffer) return -1;
    return ecex_buffer_set_major_mode_by_name(ed, buffer, "c-mode");
}

ECEX_PLUGIN_BEGIN(ecex_c_mode_plugin, C_MODE_PLUGIN_ID)
    if (!ecex_define_major_mode(ed, "c-mode")) return -1;

    ECEX_CONFIG_COMMAND("c-indent-line", cmd_c_indent_line);
    ECEX_CONFIG_COMMAND("c-complete", cmd_c_complete);
    ECEX_CONFIG_TRY(ecex_bind_mode_key(ed, "c-mode", "TAB", "c-indent-line"));
    ECEX_CONFIG_TRY(ecex_bind_mode_key(ed, "c-mode", "C-TAB", "c-complete"));
    ECEX_CONFIG_TRY(ecex_bind_mode_key(ed, "c-mode", "C-S-TAB", "complete-at-point-previous"));

    if (ecex_dependency_available("clangd")) {
        ECEX_CONFIG_TRY(ecex_add_clangd_completion_provider(ed,
                                                            C_MODE_LSP_PROVIDER_NAME,
                                                            "c-mode"));
        ecex_plugin_slot_i32_set_scalar(plugin, C_MODE_SLOT_CLANGD, 1);
    } else {
        ecex_plugin_slot_i32_set_scalar(plugin, C_MODE_SLOT_CLANGD, 0);
        ecex_message(ed, "c-mode: clangd not found; C completion disabled");
    }

    ECEX_CONFIG_TRY(ecex_plugin_file_handler_register(plugin, ".c", c_mode_file_handler));
    ECEX_CONFIG_TRY(ecex_plugin_file_handler_register(plugin, ".h", c_mode_file_handler));
    ECEX_CONFIG_TRY(ecex_plugin_file_handler_register(plugin, ".cc", c_mode_file_handler));
    ECEX_CONFIG_TRY(ecex_plugin_file_handler_register(plugin, ".cpp", c_mode_file_handler));
    ECEX_CONFIG_TRY(ecex_plugin_file_handler_register(plugin, ".cxx", c_mode_file_handler));
    ECEX_CONFIG_TRY(ecex_plugin_file_handler_register(plugin, ".hh", c_mode_file_handler));
    ECEX_CONFIG_TRY(ecex_plugin_file_handler_register(plugin, ".hpp", c_mode_file_handler));
    ECEX_CONFIG_TRY(ecex_plugin_file_handler_register(plugin, ".hxx", c_mode_file_handler));

    return 0;
ECEX_PLUGIN_END

#ifndef ECEX_NO_STANDALONE_CONFIG
ECEX_CONFIG_BEGIN
    ECEX_CONFIG_INCLUDE(ecex_c_mode_plugin);
ECEX_CONFIG_END
#endif