#include "../include/parser.h"
#include "../include/bytecode.h"
#include <stdio.h>
#include <assert.h>
#include <stdlib.h>

#define return_if_error(expr)           \
    {                                   \
        if(!(expr))                     \
            return TSL_PARSE_RESULT_ERR;\
    }

typedef struct {
    TslTokenizer tokenizer;
    TslBuffer /*TslBytecode*/ function_bytecode_list;
    TslBuffer /*int*/ function_bytecode_list_index;
} TslParser;

static int tsl_parser_get_current_function_index(TslParser *self) {
    char *last_item = (char*)tsl_buffer_end(&self->function_bytecode_list_index) - sizeof(int);
    return *(int*)last_item;
}

#define get_function_bytecode(self) ((TslBytecode*)tsl_buffer_begin(&self->function_bytecode_list) + tsl_parser_get_current_function_index(self))

static TslParseResult tsl_parser_parse_rhs(TslParser *self);
static TslParseResult tsl_parser_parse_expressions(TslParser *self, TslToken end_token);

static int tsl_parser_init(TslParser *self, char *code, size_t code_size) {
    TslBytecode bytecode_writer;
    int result1 = 1;
    int result2 = 1;
    size_t bytecode_index = 0;
    tsl_tokenizer_init(&self->tokenizer, code, code_size);
    tsl_bytecode_init(&bytecode_writer);
    tsl_buffer_init(&self->function_bytecode_list);
    tsl_buffer_init(&self->function_bytecode_list_index);
    result1 = tsl_buffer_append(&self->function_bytecode_list, &bytecode_writer, sizeof(bytecode_writer));
    result2 = tsl_buffer_append(&self->function_bytecode_list_index, &bytecode_index, sizeof(bytecode_index));
    return result1 && result2;
}

static void tsl_parser_deinit(TslParser *self) {
    TslBytecode *bytecode_writer = tsl_buffer_begin(&self->function_bytecode_list);
    TslBytecode *bytecode_writer_end = tsl_buffer_end(&self->function_bytecode_list);
    while(bytecode_writer != bytecode_writer_end) {
        tsl_bytecode_deinit(bytecode_writer);
        ++bytecode_writer;
    }
    tsl_buffer_deinit(&self->function_bytecode_list);
    tsl_buffer_deinit(&self->function_bytecode_list_index);
}

static TslParseResult tsl_parser_push_function(TslParser *self) {
    int function_index;
    TslBytecode bytecode_writer;
    tsl_bytecode_init(&bytecode_writer);
    /* TODO: Use bitshift ? */
    function_index = self->function_bytecode_list.size / sizeof(TslBytecode);
    return_if_error(tsl_buffer_append(&self->function_bytecode_list, &bytecode_writer, sizeof(bytecode_writer)));
    return tsl_buffer_append(&self->function_bytecode_list_index, &function_index, sizeof(function_index));
}

static void tsl_parser_pop_function(TslParser *self) {
    tsl_buffer_pop(&self->function_bytecode_list_index, sizeof(int));
}

static TslParseResult tsl_parser_parse_map(TslParser *self, int *num_items) {
    #define parse_map_element_separator                                             \
        return_if_error(tsl_tokenizer_accept(&self->tokenizer, TSL_TOKEN_COLON));   \
        return_if_error(tsl_parser_parse_rhs(self));                                \
        ++*num_items;                                                               \
        token = tsl_tokenizer_next(&self->tokenizer);                               \
        if(token == TSL_TOKEN_COMMA) {                                              \
            continue;                                                               \
        } else if(token == TSL_TOKEN_RBRACE) {                                      \
            return TSL_PARSE_RESULT_OK;                                             \
        } else {                                                                    \
            fprintf(stderr, "Error: Expected ',' or '}', got TODO\n");              \
            return TSL_PARSE_RESULT_ERR;                                            \
        }

    *num_items = 0;
    for(;;) {
        TslToken token = tsl_tokenizer_next(&self->tokenizer);
        if(token == TSL_TOKEN_NUM) {
            ++*num_items;
            return_if_error(tsl_bytecode_add_ins2(get_function_bytecode(self), TSL_OPCODE_LOADN, self->tokenizer.number_value));
            parse_map_element_separator
        } else if(token == TSL_TOKEN_BOOL) {
            ++*num_items;
            return_if_error(tsl_bytecode_add_ins3(get_function_bytecode(self), TSL_OPCODE_LOADB, self->tokenizer.bool_value));
            parse_map_element_separator
        } else if(token == TSL_TOKEN_NULL) {
            ++*num_items;
            return_if_error(tsl_bytecode_add_ins5(get_function_bytecode(self), TSL_OPCODE_LOADNULL));
            parse_map_element_separator
        } else if(token == TSL_TOKEN_STRING) {
            ++*num_items;
            return_if_error(tsl_bytecode_add_ins4(get_function_bytecode(self), TSL_OPCODE_LOADS, &self->tokenizer.string));
            parse_map_element_separator
        } else if(token == TSL_TOKEN_RBRACE) {
            /* '}' after trailing ',' or an empty map */
            return TSL_PARSE_RESULT_OK;
        } else {
            fprintf(stderr, "Error: Expected '}', got TODO\n");
            return TSL_PARSE_RESULT_ERR;
        }
    }
}

static TslParseResult tsl_parser_parse_list(TslParser *self, int *num_items) {
    #define parse_list_element_separator                                    \
        token = tsl_tokenizer_next(&self->tokenizer);                       \
        if(token == TSL_TOKEN_COMMA) {                                      \
            continue;                                                       \
        } else if(token == TSL_TOKEN_RBRACKET) {                            \
            return TSL_PARSE_RESULT_OK;                                     \
        } else {                                                            \
            fprintf(stderr, "Error: Expected ',' or ']', got TODO\n");      \
            return TSL_PARSE_RESULT_ERR;                                    \
        }

    *num_items = 0;
    for(;;) {
        /* TODO: Use tsl_parser_parse_rhs instead */
        TslToken token = tsl_tokenizer_next(&self->tokenizer);
        if(token == TSL_TOKEN_NUM) {
            ++*num_items;
            return_if_error(tsl_bytecode_add_ins2(get_function_bytecode(self), TSL_OPCODE_LOADN, self->tokenizer.number_value));
            parse_list_element_separator
        } else if(token == TSL_TOKEN_BOOL) {
            ++*num_items;
            return_if_error(tsl_bytecode_add_ins3(get_function_bytecode(self), TSL_OPCODE_LOADB, self->tokenizer.bool_value));
            parse_list_element_separator
        } else if(token == TSL_TOKEN_NULL) {
            ++*num_items;
            return_if_error(tsl_bytecode_add_ins5(get_function_bytecode(self), TSL_OPCODE_LOADNULL));
            parse_list_element_separator
        } else if(token == TSL_TOKEN_STRING) {
            ++*num_items;
            return_if_error(tsl_bytecode_add_ins4(get_function_bytecode(self), TSL_OPCODE_LOADS, &self->tokenizer.string));
            parse_list_element_separator
        } else if(token == TSL_TOKEN_RBRACKET) {
            /* ']' after trailing ',' or an empty list */
            return TSL_PARSE_RESULT_OK;
        } else {
            fprintf(stderr, "Error: Expected '}', got TODO\n");
            return TSL_PARSE_RESULT_ERR;
        }
    }
}

/* FN_BODY = '{' EXPRS '}' */
static TslParseResult tsl_parser_parse_fn_body(TslParser *self) {
    return_if_error(tsl_tokenizer_accept(&self->tokenizer, TSL_TOKEN_LBRACE));
    return tsl_parser_parse_expressions(self, TSL_TOKEN_RBRACE);
}

/* FN = '(' (IDENTIFIER ',')* ')' FN_BODY */
static TslParseResult tsl_parser_parse_fn(TslParser *self) {
    return_if_error(tsl_tokenizer_accept(&self->tokenizer, TSL_TOKEN_LPAREN));
    for(;;) {
        TslToken token = tsl_tokenizer_next(&self->tokenizer);
        if(token == TSL_TOKEN_RPAREN) {
            return tsl_parser_parse_fn_body(self);
        } else if(token == TSL_TOKEN_IDENTIFIER) {
            TslStringView param_name = self->tokenizer.identifier;
            printf("function parameter: |%.*s|\n", (int)param_name.size, param_name.data);
            token = tsl_tokenizer_next(&self->tokenizer);
            if(token == TSL_TOKEN_COMMA) {
                continue;
            } else if(token == TSL_TOKEN_RPAREN) {
                return tsl_parser_parse_fn_body(self);
            } else {
                fprintf(stderr, "Error: Expected ',' or ')', got TODO\n");
                return TSL_PARSE_RESULT_ERR;
            }
        } else {
            fprintf(stderr, "Error: Expected parameter name or ')', got TODO\n");
            return TSL_PARSE_RESULT_ERR;
        }
    }
}

/* VAR_INDEX = '[' RHS ']' */
static TslParseResult tsl_parser_parse_var_indexing(TslParser *self) {
    return_if_error(tsl_tokenizer_accept(&self->tokenizer, TSL_TOKEN_LBRACKET));
    return_if_error(tsl_parser_parse_rhs(self));
    return_if_error(tsl_tokenizer_accept(&self->tokenizer, TSL_TOKEN_RBRACKET));
    return tsl_bytecode_add_ins5(get_function_bytecode(self), TSL_OPCODE_INDEX);
}

/* FUNC_CALL = '(' (RHS ',')* ')' */
static TslParseResult tsl_parser_parse_func_call(TslParser *self, int *num_args) {
    *num_args = 0;
    return_if_error(tsl_tokenizer_accept(&self->tokenizer, TSL_TOKEN_LPAREN));
    for(;;) {
        TslToken token = tsl_tokenizer_peek(&self->tokenizer);
        if(token == TSL_TOKEN_RPAREN) {
            tsl_tokenizer_consume_peek(&self->tokenizer); /* consume previous TSL_TOKEN_RPAREN */
            return TSL_PARSE_RESULT_OK;
        } else {
            ++*num_args;
            return_if_error(tsl_parser_parse_rhs(self));
            token = tsl_tokenizer_next(&self->tokenizer);
            if(token == TSL_TOKEN_COMMA) {
                continue;
            } else if(token == TSL_TOKEN_RPAREN) {
                return TSL_PARSE_RESULT_OK;
            } else {
                fprintf(stderr, "Error: Expected ',' or ')', got TODO\n");
                return TSL_PARSE_RESULT_ERR;
            }
        }
    }
}

/* TODO: Allow command inside another command */
/* COMMAND = '(' TSL_COMMAND_TOKEN_ARG* ')' */
static TslParseResult tsl_parser_parse_command(TslParser *self, int *num_args) {
    *num_args = 0;
    return_if_error(tsl_tokenizer_accept(&self->tokenizer, TSL_TOKEN_LPAREN));
    for(;;) {
        TslStringView command_arg;
        TslCommandToken command_token = tsl_tokenizer_next_command_arg(&self->tokenizer, &command_arg);
        if(command_token == TSL_COMMAND_TOKEN_ARG) {
            ++*num_args;
            if(command_arg.data[0] == '$') {
                command_arg.data += 1;
                command_arg.size -= 1;
                if(command_arg.size == 0) {
                    fprintf(stderr, "Error: Expected variable name after '$'\n");
                    return TSL_PARSE_RESULT_ERR;
                }
                return_if_error(tsl_bytecode_add_ins4(get_function_bytecode(self), TSL_OPCODE_LOADV, &command_arg));
            } else {
                return_if_error(tsl_bytecode_add_ins4(get_function_bytecode(self), TSL_OPCODE_LOADS, &command_arg));
            }
        } else if(command_token == TSL_COMMAND_TOKEN_END) {
            return TSL_PARSE_RESULT_OK;
        } else {
            fprintf(stderr, "Error: Expected command argument or ')', got TODO\n");
            return TSL_PARSE_RESULT_ERR;
        }
    }
}

static TslOpcode arithmetic_symbol_to_opcode(char arithmetic_symbol) {
    switch(arithmetic_symbol) {
        case '+':   return TSL_OPCODE_ADD;
        case '-':   return TSL_OPCODE_SUB;
        case '*':   return TSL_OPCODE_MUL;
        case '/':   return TSL_OPCODE_DIV;
        default:
            fprintf(stderr, "Unexpected arithmetic symbol: %c\n", arithmetic_symbol);
            abort();
    }
}

/* RHS_SUB = (VAR_INDEX|FUNC_CALL RHS_SUB?)|(TOKEN_ARITHMETIC RHS) */
static TslParseResult tsl_parser_parse_rhs_sub(TslParser *self) {
    TslToken token = tsl_tokenizer_peek(&self->tokenizer);
    if(token == TSL_TOKEN_LBRACKET) {
        return_if_error(tsl_parser_parse_var_indexing(self));
        return tsl_parser_parse_rhs_sub(self);
    } else if(token == TSL_TOKEN_LPAREN) {
        int num_args;
        return_if_error(tsl_parser_parse_func_call(self, &num_args));
        return_if_error(tsl_bytecode_add_ins1(get_function_bytecode(self), TSL_OPCODE_CALLF, num_args));
        return tsl_parser_parse_rhs_sub(self);
    } else if(token == TSL_TOKEN_ARITHMETIC) {
        TslOpcode arithmetic_opcode;
        tsl_tokenizer_consume_peek(&self->tokenizer); /* consume previous TSL_TOKEN_ARITHMETIC */
        arithmetic_opcode = arithmetic_symbol_to_opcode(self->tokenizer.arithmetic_symbol);
        /* TODO: Handle arithmetic expression precedence */
        return tsl_parser_parse_rhs(self) && tsl_bytecode_add_ins5(get_function_bytecode(self), arithmetic_opcode);
    }
    /*
        No sub expression found, possibly a new expression after this (a new expression on a new line), let that
        part of the code handle error if there is any instead.
    */
    return TSL_PARSE_RESULT_OK;
}

/* RHS_SUB_ARITHMETIC = TOKEN_ARITHMETIC RHS */
static TslParseResult tsl_parser_parse_rhs_sub_arithmetic(TslParser *self) {
    TslToken token = tsl_tokenizer_peek(&self->tokenizer);
    if(token == TSL_TOKEN_ARITHMETIC) {
        tsl_tokenizer_consume_peek(&self->tokenizer); /* consume previous TSL_TOKEN_ARITHMETIC */
        printf("rhs sub arithmetic symbol: %c\n", self->tokenizer.arithmetic_symbol);
        /* TODO: Handle arithmetic expression precedence */
        return tsl_parser_parse_rhs(self);
    }
    /*
        No sub expression found, possibly a new expression after this (a new expression on a new line), let that
        part of the code handle error if there is any instead.
    */
    return TSL_PARSE_RESULT_OK;
}

/* RHS = (IDENTIFIER|NUM|BOOL|NULL|STRING|MAP|LIST|('fn' FN)|('$' COMMAND)) RHS_SUB? */
TslParseResult tsl_parser_parse_rhs(TslParser *self) {
    TslToken token = tsl_tokenizer_next(&self->tokenizer);
    switch(token) {
        case TSL_TOKEN_IDENTIFIER: {
            TslStringView var_name = self->tokenizer.identifier;
            return_if_error(tsl_bytecode_add_ins4(get_function_bytecode(self), TSL_OPCODE_LOADV, &var_name));
            return tsl_parser_parse_rhs_sub(self);
        }
        case TSL_TOKEN_NUM:
            return_if_error(tsl_bytecode_add_ins2(get_function_bytecode(self), TSL_OPCODE_LOADN, self->tokenizer.number_value));
            return tsl_parser_parse_rhs_sub_arithmetic(self);
        case TSL_TOKEN_BOOL:
            return tsl_bytecode_add_ins3(get_function_bytecode(self), TSL_OPCODE_LOADB, self->tokenizer.bool_value);
        case TSL_TOKEN_NULL:
            return tsl_bytecode_add_ins5(get_function_bytecode(self), TSL_OPCODE_LOADNULL);
        case TSL_TOKEN_STRING:
            return tsl_bytecode_add_ins4(get_function_bytecode(self), TSL_OPCODE_LOADS, &self->tokenizer.string);
        case TSL_TOKEN_LBRACE: {
            int num_items;
            return tsl_parser_parse_map(self, &num_items) &&
                tsl_bytecode_add_ins1(get_function_bytecode(self), TSL_OPCODE_MAP, num_items);
        }
        case TSL_TOKEN_LBRACKET: {
            int num_items;
            return tsl_parser_parse_list(self, &num_items) &&
                tsl_bytecode_add_ins1(get_function_bytecode(self), TSL_OPCODE_LIST, num_items);
        }
        case TSL_TOKEN_FN: {
            int function_index;
            return_if_error(tsl_parser_push_function(self));
            return_if_error(tsl_parser_parse_fn(self));
            function_index = tsl_parser_get_current_function_index(self);
            tsl_parser_pop_function(self);
            return tsl_bytecode_add_ins1(get_function_bytecode(self), TSL_OPCODE_LOADF, function_index);
        }
        case TSL_TOKEN_DOLLAR_SIGN: {
            int num_args;
            return_if_error(tsl_parser_parse_command(self, &num_args))
            if(num_args == 0) {
                fprintf(stderr, "Error: Command can't be empty\n");
                return TSL_PARSE_RESULT_ERR;
            }
            return tsl_bytecode_add_ins1(get_function_bytecode(self), TSL_OPCODE_CALLC, num_args);
        }
        default:
            fprintf(stderr, "Error: Expected variable, number, bool, null, map, list, function or command, got TODO (%d) (line: %d)\n", token, tsl_tokenizer_get_line_by_index(&self->tokenizer, self->tokenizer.prev_code_index));
            return TSL_PARSE_RESULT_ERR;
    }
}

/*
    EXPR = IDENTIFIER ('=' RHS)|RHS_SUB
    EXPRS = EXPR*
*/
TslParseResult tsl_parser_parse_expressions(TslParser *self, TslToken end_token) {
    for(;;) {
        TslToken token = tsl_tokenizer_next(&self->tokenizer);
        if(token == TSL_TOKEN_IDENTIFIER) {
            TslStringView identifier = self->tokenizer.identifier;
            if(tsl_tokenizer_peek(&self->tokenizer) == TSL_TOKEN_EQUAL) {
                tsl_tokenizer_consume_peek(&self->tokenizer); /* consume previous TSL_TOKEN_EQUAL */
                return_if_error(tsl_parser_parse_rhs(self));
                return_if_error(tsl_bytecode_add_ins4(get_function_bytecode(self), TSL_OPCODE_SETV, &identifier));
                /* TODO: Assert if there are load bytecode opcodes not followed by set */
            } else {
                return_if_error(tsl_bytecode_add_ins4(get_function_bytecode(self), TSL_OPCODE_LOADV, &identifier));
                return_if_error(tsl_parser_parse_rhs_sub(self));
            }
        } else if(token == end_token) {
            break;
        } else {
            fprintf(stderr, "Error: Expected identifier, got TODO\n");
            return TSL_PARSE_RESULT_ERR;
        }
    }
    return TSL_PARSE_RESULT_OK;
}

TslParseResult tsl_parse(char *code, size_t code_size, TslProgram *program_output) {
    TslParseResult result;
    TslParser parser;

    assert(code);
    assert(program_output);

    tsl_program_init(program_output);
    return_if_error(tsl_parser_init(&parser, code, code_size));

    result = tsl_parser_parse_expressions(&parser, TSL_TOKEN_END_OF_FILE);
    if(result == TSL_PARSE_RESULT_OK)
        tsl_buffer_move(&program_output->function_bytecode_list, &parser.function_bytecode_list);

    tsl_parser_deinit(&parser);
    return result;
}