// === 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();

    while (!is_end_of_list(token))
    {
        if (token->type == TOKEN_SEMICOLON)
        {
            result_list = list_append(result_list, current_node);
        }
        else
        {
            current_node = parse_and_or();
        }
        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();

    while (token->type == TOKEN_WORD)
    {
        token = POP_TOKEN();
        command_elements = list_append(command_elements, token->data);
        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)
{
    struct token *token = PEEK_TOKEN();

    switch (token->type)
    {
    case TOKEN_IF:
        return parse_if_rule();

    default:
        puts("I think it's not implemented yet");
        return NULL;
    }
}

// TODO check compliance with the grammar
struct ast *parse_if_rule(void)
{
    // If condition
    struct token *token = POP_TOKEN();

    if (token->type != TOKEN_IF)
    {
        puts("Internal error: expected a if rule but token has different "
             "type");
        return NULL;
    }

    struct ast *condition_content = parse_compound_list();

    // Then content
    token = POP_TOKEN();

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

    struct ast *then_content = parse_compound_list();

    // Eventual else/elif clause(s)
    struct ast *else_content = parse_else_clause();

    token = POP_TOKEN();
    if (token->type != TOKEN_FI)
    {
        puts("Expected the 'fi' keyword but token has different type");
        // TODO free previous asts
        return NULL;
    }

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

    return result;
}

// TODO comply with header's grammar
struct ast *parse_compound_list(void)
{
    struct list *result_list = NULL; // ast* list
    struct list *command_elements = NULL; // token* list
    struct token *token = PEEK_TOKEN();

    while (token->type != TOKEN_THEN || token->type != TOKEN_ELIF
           || token->type != TOKEN_ELSE)
    {
        // Parse simple command
        if (token->type == TOKEN_SEMICOLON || token->type == TOKEN_NEWLINE)
        {
            // Stage (-> next command)
            struct ast *command = ast_create_command(command_elements);
            result_list = list_append(result_list, command);
            command_elements = NULL;
        }

        if (token->type == TOKEN_EOF)
        {
            puts("Syntax error: Unexpected end of stream"); // TODO pas très
                                                            // bien dit
            return NULL;
        }

        command_elements = list_append(command_elements, token->data);
        token = POP_TOKEN();
    }

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

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

    // TODO handle ELIF
    // 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;
}