// === Includes
#include "parsing_utils.h"

#include <stdbool.h>
#include <stddef.h>
#include <stdio.h>

#include "lexer/lexer.h"
#include "utils/ast/ast.h"

// === Static functions

/* Returns true if c is a command terminator, false otherwise
 */
static bool isterminator(struct token *token)
{
    if (token == NULL)
        return false;

    switch (token->type)
    {
    case TOKEN_NEWLINE:
    case TOKEN_SEMICOLON:
    case TOKEN_EOF:
        return true;
    default:
        return false;
    }
}

/* @brief: returns true if token is an end of list indicator.
 */
static bool is_end_of_list(struct token *token)
{
    if (token == NULL)
        return false;

    switch (token->type)
    {
    case TOKEN_NEWLINE:
    case TOKEN_EOF:
        return true;
    default:
        return false;
    }
}

// === Functions

struct ast *parse_input(void)
{
    return parse_list();
}

struct ast *parse_list(void)
{
    struct list *result_list = NULL;
    struct ast *current_node = NULL;

    struct token *token = PEEK_TOKEN();

    // and_or
    current_node = parse_and_or();
    if (current_node == NULL)
        return NULL;
    list_append(result_list, current_node);

    // Following and_or commands
    token = PEEK_TOKEN();
    while (token->type == TOKEN_SEMICOLON)
    {
        token = POP_TOKEN();
        if (!isterminator(token)) // Follow(list)
        {
            current_node = parse_and_or();
            if (current_node == NULL)
            {
                //TODO free list
                // There must be a function for that
                return NULL;
            }
            list_append(result_list, current_node);
            token = PEEK_TOKEN();
        }
    }

    return ast_create_list(result_list);
}

struct ast *parse_and_or(void)
{
    return parse_pipeline();
}

struct ast *parse_pipeline(void)
{
    return parse_command();
}

struct ast *parse_command(void)
{
    struct token *token = PEEK_TOKEN();

    if (token->type == TOKEN_WORD)
    {
        return parse_simple_command();
    }
    else if (token->type == TOKEN_IF)
    {
        return parse_shell_command();
    }
    else
    {
        return ast_create_void(); // TODO not sure what to do
    }
}

struct ast *parse_simple_command(void)
{
    struct list *command_elements = NULL;
    struct token *token = PEEK_TOKEN();
    if (token->type != TOKEN_WORD)
    {
        puts("Expected a command but got a different token type");
        return NULL;
    }

    while (token->type == TOKEN_WORD)
    {
        token = POP_TOKEN();
        char* word = strdup(token->data);
        command_elements = list_append(command_elements, word);
        token = PEEK_TOKEN();
    }

    struct ast *result = ast_create_command(command_elements);
    return result;
}

// TODO check compliance with the grammar
struct ast *parse_shell_command(void)
{
    return parse_if_rule();
}

struct ast *parse_if_rule(void)
{
    // If keyword
    struct token *token = POP_TOKEN();
    if (token->type != TOKEN_IF)
    {
        puts("Internal error: expected a if rule but token has different "
             "type");
        return NULL;
    }

    // Condition content
    struct ast *condition_content = parse_compound_list();

    // Then keyword
    token = POP_TOKEN();
    if (token->type != TOKEN_THEN)
    {
        ast_free(&condition_content);
        puts("Expected the 'then' keyword but token has different type");
        return NULL;
    }

    // Then content
    struct ast *then_content = parse_compound_list();
    if (then_content == NULL)
    {
        ast_free(&condition_content);
        ast_free(&then_content);
        return NULL;
    }

    // Eventual else/elif clause(s)
    struct ast *else_content = parse_else_clause();
    if (else_content == NULL)
    {
        ast_free(&condition_content);
        ast_free(&then_content);
        return NULL;
    }

    token = POP_TOKEN();
    if (token->type != TOKEN_FI)
    {
        ast_free(&condition_content);
        ast_free(&then_content);
        ast_free(&else_content);
        puts("Expected the 'fi' keyword but token has different type");
        return NULL;
    }

    struct ast *result =
        ast_create_if(condition_content, then_content, else_content);
    if (result == NULL)
    {
        ast_free(&condition_content);
        ast_free(&then_content);
        ast_free(&else_content);
        puts("Internal error: could not create a new AST (AST_IF)");
        return NULL;
    }

    return result;
}

struct ast *parse_compound_list(void)
{
    struct list *result_list = NULL; // ast* list
    struct ast *current_cmd = NULL;
    struct token *token = PEEK_TOKEN();

    // Skip newlines
    while (token == TOKEN_NEWLINE)
        token = POP_TOKEN();

    // and_or
    current_cmd = parse_and_or();
    if (current_cmd == NULL)
        return NULL;
    list_append(result_list, current_cmd);
    
    // Following commands
    token = PEEK_TOKEN();
    while (token->type == TOKEN_SEMICOLON || token->type TOKEN_NEWLINE)
    {
        POP_TOKEN();

        // Skip newlines
        while (token == TOKEN_NEWLINE)
            token = POP_TOKEN();

        // and_or
        current_cmd = parse_and_or();
        if (current_cmd == NULL)
            return NULL;
        list_append(result_list, current_cmd);

        token = PEEK_TOKEN();
    }

    // Eventual semicolons
    if (token->type == TOKEN_SEMICOLON)
        token = POP_TOKEN();

    // Skip newlines
    while (token == TOKEN_NEWLINE)
        token = POP_TOKEN();
    

    struct ast *result = ast_create_list(result_list);
    return result;
}

struct ast *parse_else_clause(void)
{
    struct token *token = PEEK_TOKEN();

    // Eventual elif content
    while (token->type == TOKEN_ELIF)
    {
        // Condition
        token = POP_TOKEN();
        struct ast *condition = parse_compound_list();

        // 'then'
        token = POP_TOKEN();
        if (token->type != TOKEN_THEN)
        {
            puts("Expected the 'then' keyword but got a different token type");
            return NULL;
        }

        // Then clause
        struct ast *then_content = parse_compound_list();

        // Eventual else clause (recursive)
        struct ast *else_content = NULL;
        token = PEEK_TOKEN();
        if (token->type == TOKEN_ELSE || token_type == TOKEN_ELIF)
        {
            else_content = parse_else_clause();
        }

        struct ast *result =
            ast_create_if(condition, then_content, else_content);
        return result;
    }

    // Eventual else content

    struct ast *result = NULL;

    if (token->type == TOKEN_ELSE)
    {
        result = parse_compound_list();
        token = POP_TOKEN(); // Forward
    }

    if (result == NULL)
        result = ast_create_void();

    return result;
}