#ifndef CMETA_H
#define CMETA_H

#include <stddef.h>

typedef struct {
    const char* type;
    const char* name;
} Field_Info;

typedef struct {
    const char* name;
    size_t fields_count;
    Field_Info *fields;
} Struct_Info;

// AUTO GENERATED CODE  //
// AUTO GENERATED CODE  //

// #define CMETA_COMPTIME
#ifdef CMETA_COMPTIME

#include <ctype.h>
#include <errno.h>
#include <stdbool.h>
#include <stdio.h>
#include <string.h>

#define STB_C_LEXER_IMPLEMENTATION
#include "stb_c_lexer.h"

stb_lexer lexer = {0};

typedef struct {
    char* type;
    char* name;
} Parsed_Field_Info;

typedef struct {
    Parsed_Field_Info* items;
    size_t count;
    size_t capacity;
} Parsed_Field_Infos;

typedef struct {
    char* name;
    size_t fields_count;
    Parsed_Field_Info *fields;
} Parsed_Struct_Info;

typedef struct {
    Parsed_Struct_Info* items;
    size_t count;
    size_t capacity;
} Parsed_Struct_Infos;

typedef struct {
    char* data;
    size_t capacity;
    size_t length;
} String_Builder;

void sb_append(String_Builder* sb, const char* data) {
    size_t data_len = strlen(data);
    size_t total_len = sb->length + data_len;

    if (total_len + 1 > sb->capacity) {
        size_t new_capacity = sb->capacity == 0 ? 64 : sb->capacity * 2;
        while (new_capacity < total_len + 1) {
            new_capacity *= 2;
        }
        sb->data = (char*) realloc(sb->data, new_capacity);
        sb->capacity = new_capacity;
    }

    memcpy(sb->data + sb->length, data, data_len);
    sb->length = total_len;
    sb->data[sb->length] = '\0';
}

#define da_append(da, item)                                                          \
    do {                                                                             \
        if ((da)->count + 1 > (da)->capacity) {                                      \
            size_t new_capacity = (da)->capacity == 0 ? 64 : (da)->capacity * 2;     \
            while ((da)->count + 1 > new_capacity) {                                 \
                new_capacity *= 2;                                                   \
            }                                                                        \
            (da)->items = realloc((da)->items, new_capacity * sizeof(*(da)->items)); \
        }                                                                            \
        (da)->items[(da)->count++] = (item);                                         \
    } while (0)                                                                      \

bool lexer_expect_keyword(const char* expected) {
    stb_c_lexer_get_token(&lexer);

    if (lexer.token != CLEX_id) {
        // TODO: map lexer.token to readable name
        fprintf(stderr, "ERROR: expected `%s` but got `%ld`\n", expected, lexer.token);
        return false;        
    }

    if (strcmp(lexer.string, expected) != 0) {
        fprintf(stderr, "ERROR: expected `%s` but got `%s`\n", expected, lexer.string);
        return false;
    }

    return true;
}

bool lexer_expect(long expected, const char* expected_str) {
    stb_c_lexer_get_token(&lexer);

    if (lexer.token != expected) {
        // TODO: map lexer.token to readable name
        if(expected_str != NULL) {
            fprintf(stderr, "ERROR: expected %s but got `%ld`\n", expected_str, lexer.token);
        } else {
            fprintf(stderr, "ERROR: expected `%ld` but got `%ld`\n", expected, lexer.token);
        }
        return false;        
    }

    return true;
}

long lexer_peek() {
    char* mark = lexer.parse_point;
    if (!stb_c_lexer_get_token(&lexer)) {
        lexer.parse_point = mark;
        return CLEX_eof;
    }

    long token = lexer.token;
    lexer.parse_point = mark;

    return token;
}

// parses typedef struct { FIELDS } TYPE_NAME
bool parse_struct(Parsed_Struct_Info* info) {
    bool result = false;
    char* name = NULL;

    Parsed_Field_Infos fields = {0};

    if (!lexer_expect_keyword("typedef")) goto fail;
    if (!lexer_expect_keyword("struct")) goto fail;
    if (!lexer_expect('{', NULL)) goto fail;

    while (true) {
        char* mark = lexer.parse_point;
        if (!stb_c_lexer_get_token(&lexer)) {
            fprintf(stderr, "ERROR: expected struct fields but got EOF\n");
            goto fail;
        }

        if (lexer.token == '}') break;
        lexer.parse_point = mark;

        if (!lexer_expect(CLEX_id, "field type")) goto fail;
        char* field_type = strdup(lexer.string);

        if (!lexer_expect(CLEX_id, "field name")) goto fail;
        char* field_name = strdup(lexer.string);

        Parsed_Field_Info field = {
            .type = field_type,
            .name = field_name,
        };
        da_append(&fields, field);

        if(!lexer_expect(';', NULL)) goto fail;
    }

    if (!lexer_expect(CLEX_id, "type name")) goto fail;
    name = strdup(lexer.string);

    info->name = name;
    info->fields_count = fields.count;
    info->fields = (Parsed_Field_Info*)calloc(info->fields_count, sizeof(Parsed_Field_Info));
    for(size_t i = 0; i < info->fields_count; i += 1) {
        info->fields[i].type = fields.items[i].type;
        info->fields[i].name = fields.items[i].name;
    }

    result = true;
fail:
    if(!result) {
        free(name);
        for(size_t i = 0; i < fields.count; i += 1) {
            free(fields.items[i].name);
            free(fields.items[i].type);
        }
        free(fields.items);
    }

    return result;
}

void print_struct(Parsed_Struct_Info info) {
    printf("struct_name = %s\n", info.name);
    printf("fields[%zu] = [\n", info.fields_count);
    for (size_t i = 0; i < info.fields_count; i += 1) {
        printf("    { type = %s, name = %s },\n", info.fields[i].type, info.fields[i].name);
    }
    printf("]\n");
}

#define gen(...) do {                                       \
        fprintf(stream, __VA_ARGS__);                       \
        fprintf(stream, " // %s:%d\n", __FILE__, __LINE__); \
    } while(0)

char* to_lowercase(char* str) {
    size_t len = strlen(str);
    for(size_t i = 0; i < len; i += 1) {
        str[i] = tolower(str[i]);
    }
    return str;
}

void generate_struct_info(FILE* stream, Parsed_Struct_Info info) {
    char* lowercase_name = to_lowercase(strdup(info.name));

    gen("static Struct_Info %s_info = {", lowercase_name);
    gen("    .name = \"%s\",", info.name);
    gen("    .fields_count = %zu,", info.fields_count);
    gen("    .fields = (Field_Info[%zu]) {", info.fields_count);
    for (size_t i = 0; i < info.fields_count; i += 1) {
        gen("        { .type = \"%s\", .name = \"%s\" },", info.fields[i].type, info.fields[i].name);
    }
    gen("    },");
    gen("};");
    
    free(lowercase_name);
}

bool read_entire_file(const char* file_path, char** content) {
    bool result = false;
    FILE* file = fopen(file_path, "rb");
    if(file == NULL) goto fail;

    if(fseek(file, 0, SEEK_END) < 0) goto fail;
    
    long length = ftell(file);
    if(length < 0) goto fail;

    if(fseek(file, 0, SEEK_SET) < 0) goto fail;

    *content = (char*) malloc((length + 1) * sizeof(char));
    fread(*content, 1, length, file);

    // TODO: will not set errno
    if (ferror(file)) goto fail;

    (*content)[length] = '\0';

    result = true;
fail:
    if (!result) {
        free(*content);
        fprintf(stderr, "ERROR: Could not read `%s`: %s\n", file_path, strerror(errno));
    }
    if (file) fclose(file);
    return result;
}

bool generate_output_file(const char* output_path, Parsed_Struct_Infos struct_infos) {
    const char* GENERATION_MARK = "// AUTO GENERATED CODE  //\n";
    const size_t GENERATION_MARK_LEN = strlen(GENERATION_MARK);

    bool result = false;
    
    char* header_content;
    if (!read_entire_file(__FILE__, &header_content)) goto fail;

    // 1. find BEGIN an END
    char* generate_begin = strstr(header_content, GENERATION_MARK);
    if (generate_begin == NULL) {
        fprintf(stderr, "ERROR: could not found generation mark in cmeta.h\n");
        goto fail;
    }

    char* generate_end = strstr(generate_begin + GENERATION_MARK_LEN, GENERATION_MARK);
    if (generate_end == NULL) {
        fprintf(stderr, "ERROR: could not found generation mark in cmeta.h\n");
        goto fail;
    }

    FILE* output_file = fopen(output_path, "wb");
    if (!output_file) {
        fprintf(stderr, "ERROR: could not write to %s: %s\n", output_path, strerror(errno));
        goto fail;
    }

    FILE* stream = output_file;

    // write up to the generation mark, including it
    fwrite(header_content, generate_begin + GENERATION_MARK_LEN - header_content, 1, stream);

    for (size_t i = 0; i < struct_infos.count; i += 1) {
        generate_struct_info(stream, struct_infos.items[i]);
    }

    fwrite(generate_end, strlen(generate_end), 1, stream);

    result = true;
fail:
    free(header_content);
    if (output_file) fclose(output_file);

    return result;
}

bool preprocess_file(const char* file_path, String_Builder* result) {
    char command[256] = {0};
    sprintf(command, "gcc -E %s", file_path);

    FILE* fp = popen(command, "r");
    if (fp == NULL) {
        fprintf(stderr, "ERROR: Failed to run command: %s\n", strerror(errno));
        return false;
    }

    char line[512];
    size_t line_num = 0;
    char file_name[512];

    size_t cursor = 0;
    result->length = 0;

    bool collecting_content = false;

    while (fgets(line, sizeof(line), fp) != NULL) {
        if (sscanf(line, "# %zu \"%s\"", &line_num, file_name) == 2) {
            // remove trailing "
            file_name[strlen(file_name) - 1] = '\0';

            if (strcmp(file_name, file_path) == 0) {
                collecting_content = true;
                continue;
            }
        } else if(collecting_content) {
            sb_append(result, line);
            cursor += strlen(line);
        }
    }

    pclose(fp);

    return true;
}

bool process_file(const char* input_file) {
    // read input file
    String_Builder input_content = {0};
    if (!preprocess_file(input_file, &input_content)) return false;

    // init lexer
    char string_store[1024] = {0};
    stb_c_lexer_init(&lexer, input_content.data, input_content.data + input_content.length, string_store, sizeof(string_store) / sizeof(char));

    // find and parse all structs
    Parsed_Struct_Infos struct_infos = {0};

    while (true) {
        char* mark = lexer.parse_point;

        if (!stb_c_lexer_get_token(&lexer)) break;
        if (lexer.token == CLEX_id && strcmp(lexer.string, "typedef") == 0) {
            lexer.parse_point = mark;

            Parsed_Struct_Info struct_info = {0};
            if (parse_struct(&struct_info)) {
                da_append(&struct_infos, struct_info);  
            }
        }    
    }

    if (!generate_output_file(__FILE__, struct_infos)) return false;

    return true;
}

#endif // CMETA_COMPTIME

#endif // CMETA_H