#include <stdlib.h>
#include <string.h>
#include <errno.h>

#include "common.h"
#include "parser.h"

// TODO: Do all the todos

// adds another child of type type to the sexp sexp 
// returns the index of the added type and < 0 on fail
static size_t sexp_add(struct sexp *sexp, enum ast_type type);

// self-explanatory
static void sexp_init(struct sexp *sexp);
static void sexp_print(struct sexp *sexp, int indent);
static void sexp_free(struct sexp *sexp);
static void ast_free(struct ast *ast);

static void quote_stack_push(struct quote_node **head, struct sexp *cur_sexp);
static struct sexp *quote_stack_pop(struct quote_node **head, int peek);

// returns 0 on success
enum paren_type { P_OPEN, P_CLOSE };
static int on_paren(parser_t parser, enum paren_type type); // 0 is open, 1 is close
static int on_quote(parser_t parent);
static int on_value(parser_t parent, value_t value);

#define TOKEN_CALLBACK_TBL(X, parser, token)           \
/*  X(test,                 execute on succes) */      \
    X(TOKEN_PARENTHS_OPEN,  on_paren(parser, P_OPEN))  \
    X(TOKEN_PARENTHS_CLOSE, on_paren(parser, P_CLOSE)) \
    X(TOKEN_SPECIAL_QUOTE,  on_quote(parser))          \
    X(TOKEN_VALUE,          on_value(parser, token->value))

#define FN(fn, arg) "%s", fn(arg, buf, buf_sz)

#define MANAGE_AST_TBL(X, ast)                                            \
    X(AST_SEXP,  sexp_free(&ast->sexp), "|")                              \
    X(AST_VALUE, value_destroy(ast->value), FN(value_string, ast->value)) \

// ---------- Exported Functions ---------- //

#define CASE_TYPE(type, callback)               \
    case type:                                  \
    if(callback) {                              \
        err(#callback ": failed");              \
        return -1;                              \
    } break;

int parser_parse_toklist(parser_t parser, toklist_t *toklist, ast_t *ast)
{
    if(parser->cur_sexp == NULL) {
        size_t index = sexp_add(&ast->sexp, AST_VALUE);
        ast->sexp.children[index].value = value_copy(parser->begin_symbol_value);
        
        parser->cur_sexp = &ast->sexp;
    }
    
    
    for(size_t i = 0; i < toklist->ntokens; i++) {
        struct token *token = &toklist->tokens[i];

        switch(token->type) {
            TOKEN_CALLBACK_TBL(CASE_TYPE, parser, token);
        default:
            err("parser_parse_lexer: Unknown token type given");
            break;
        }
        
        if(token->type != TOKEN_SPECIAL_QUOTE) 
           while(parser->cur_sexp == quote_stack_pop(&parser->quote_head, 1)) {
               on_paren(parser, P_CLOSE);
               quote_stack_pop(&parser->quote_head, 0);
           }
    }

    if(&ast->sexp == parser->cur_sexp) {
        return 0;
    } else {
        return 1;
    }
}

parser_t parser_create()
{   
    parser_t parser = xmalloc(sizeof(struct parser));

#define VALUE_CREATE(str)                  \
    value_create(VALUE_SYMBOL, str, &ret); \
    if(ret) {                              \
        err("value_create: failed");       \
        return NULL;                       \
    }

    int ret = 0;
    parser->begin_symbol_value = VALUE_CREATE("begin");
    parser->quote_symbol_value = VALUE_CREATE("quote");

    parser->quote_head = NULL;
    parser_reset(parser);

    return parser;
}

void parser_destroy(parser_t parser)
{
    if(!parser) return;

    value_destroy(parser->begin_symbol_value);
    value_destroy(parser->quote_symbol_value);
    
    parser_reset(parser);
    free(parser);
}

void parser_reset(parser_t parser)
{
    parser->cur_sexp = NULL;
    while(quote_stack_pop(&parser->quote_head, 0) != NULL);
}

void ast_reset(ast_t *ast)
{
    sexp_free(&ast->sexp);
    sexp_init(&ast->sexp);
}


void ast_print(ast_t *ast)
{
    sexp_print(&ast->sexp, 0);
}

// ---------- Callback Functions ---------- //

static int on_paren(parser_t parser, enum paren_type type)
{    
    if(type == P_CLOSE) {
        parser->cur_sexp = parser->cur_sexp->prev;
    } else if(type == P_OPEN) {
        size_t index = sexp_add(parser->cur_sexp, AST_SEXP);

        struct sexp *prev = parser->cur_sexp;
        struct sexp *new = &prev->children[index].sexp;
        
        sexp_init(new);
        
        parser->cur_sexp = new;
        parser->cur_sexp->prev = prev;
    }

    return 0;
}

static int on_quote(parser_t parser)
{
    // new sexp
    on_paren(parser, P_OPEN);

    // add symbol to the sexp
    on_value(parser, parser->quote_symbol_value);

    // save the current quote sexp
    quote_stack_push(&parser->quote_head, parser->cur_sexp);
    return 0;
}

static int on_value(parser_t parser, value_t value)
{    
    size_t index = sexp_add(parser->cur_sexp, AST_VALUE);

    value_t copied = value_copy(value);

    parser->cur_sexp->children[index].value = copied;
    return 0;
}

// ---------- Parser Functions ---------- //

static size_t sexp_add(struct sexp *sexp, enum ast_type type)
{   
    sexp->children = xrealloc(sexp->children, sizeof(struct ast) * (sexp->nchildren+1));

    sexp->children[sexp->nchildren].type = type;
    return sexp->nchildren++;
}

static void sexp_init(struct sexp *sexp)
{
    sexp->children = NULL;
    sexp->nchildren = 0;
    sexp->prev = NULL;
}

static void sexp_print(struct sexp *sexp, int indent)
{
    // (void)indent;
    // printf("( ");
    for(size_t i = 0; i < sexp->nchildren; i++) {
        struct ast *child = &sexp->children[i];

        if(child->type == AST_SEXP) {
            sexp_print(&child->sexp, indent + 2);
            continue;
        }

        char buf[LEXER_IDEN_CAP];
        size_t buf_sz = LEXER_IDEN_CAP;

        for(int i = 0; i < indent; i++) printf(" ");
        printf("%s\n", value_string(child->value, buf, buf_sz));
    }
    // printf(")");
}

static void sexp_free(struct sexp *sexp)
{
    for(size_t i = 0; i < sexp->nchildren; i++){
        ast_free(&sexp->children[i]);
    }
    
    if(sexp->children) free(sexp->children);
}

#define CASE_FREE(type, free_func, print_func)  \
    case type: free_func; return;

static void ast_free(struct ast *ast)
{
    if(!ast) return;

    switch(ast->type) {
        MANAGE_AST_TBL(CASE_FREE, ast)
    default:
        err("ast_free: Unknown ast type given");
        break;
    }
}

static void quote_stack_push(struct quote_node **head, struct sexp *cur_sexp)
{
    struct quote_node *node = xmalloc(sizeof(struct quote_node));

    node->prev = *head;
    node->cur_sexp = cur_sexp;
    *head = node;
}

static struct sexp *quote_stack_pop(struct quote_node **head, int peek)
{
    if(*head == NULL) {
        return NULL;
    }

    struct sexp *sexp = (*head)->cur_sexp;
    
    if(!peek) {
        struct quote_node *prev = (*head)->prev;
        free(*head);
        *head = prev;
    }
    
    return sexp;
}