#include "lc.h"

#include "util.h"

#include <stdarg.h>
#include <stdbool.h>

static LambdaTerm *make_variable(char *name, size_t name_len) {
    LambdaTerm *term = malloc_safe(sizeof(LambdaTerm));
    term->type = TYPE_VARIABLE;
    term->v.name = name;
    term->v.name_len = name_len;
    return term;
}

static LambdaTerm *make_lambda(char *arg, size_t arg_len, LambdaTerm *body) {
    LambdaTerm *term = malloc_safe(sizeof(LambdaTerm));
    term->type = TYPE_LAMBDA;
    term->l.arg = arg;
    term->l.arg_len = arg_len;
    term->l.body = body;
    return term;
}

static LambdaTerm *make_apply(LambdaTerm *func, LambdaTerm *arg) {
    LambdaTerm *term = malloc_safe(sizeof(LambdaTerm));
    term->type = TYPE_APPLY;
    term->a.func = func;
    term->a.arg = arg;
    return term;
}

static bool is_lambda_term_token(const Token *tok) {
    switch (tok->type) {
    case TOKEN_BACKSLASH:
    case TOKEN_OPEN_PAREN:
    case TOKEN_CLOSE_PAREN:
    case TOKEN_IDENT:
        return true;
    case TOKEN_LET:
    case TOKEN_EVAL:
    case TOKEN_CONF:
    case TOKEN_EQUALS:
    case TOKEN_COLON:
    case TOKEN_DEFINE:
    case TOKEN_REDUCE:
    case TOKEN_EOF:
        return false;
    default:
        abort();
    }
}

enum OperatorType {
    OPER_APPLY,
    OPER_DEFINE,
};

struct OperatorStack {
    struct OperatorStack *next;
    Token src;
    enum OperatorType type;
};

static struct OperatorStack *push_oper(struct OperatorStack *restrict stack,
                                       const Token *restrict src,
                                       enum OperatorType type) {
    struct OperatorStack *new = malloc_safe(sizeof(struct OperatorStack));
    new->next = stack;
    new->src = *src;
    new->type = type;
    return new;
}

enum OperandType {
    OPAND_TERM,
    OPAND_OPEN_PAREN,
    OPAND_DEF_BEGIN,
};

struct OperandStack {
    struct OperandStack *next;
    Token src;
    enum OperandType type;
    LambdaTerm *term;
};

static struct OperandStack *push_opand(struct OperandStack *restrict stack,
                                       const Token *restrict src,
                                       enum OperandType type, ...) {
    struct OperandStack *new = malloc_safe(sizeof(struct OperandStack));
    new->next = stack;
    new->src = *src;
    new->type = type;
    if (type == OPAND_TERM) {
        va_list args;
        va_start(args, type);
        new->term = va_arg(args, LambdaTerm *);
        va_end(args);
    }
    return new;
}

static void apply_one(struct OperatorStack **oper_stack,
                      struct OperandStack **opand_stack,
                      ParseError *restrict err_out) {
    if (!*oper_stack) {
        abort();
    } else if () {
    }
}

LambdaTerm *read_lambda_term(TokenStream *restrict stream,
                             ParseError *restrict err_out) {
    ParseError backup_err;
    if (!err_out) {
        err_out = &backup_err;
    }
    struct OperatorStack *oper_stack = NULL;
    struct OperandStack *opand_stack = NULL;
    Token tok;
    while (true) {
        if (!token_stream_peek(stream, &tok, err_out)) {
            return false;
        } else if (!is_lambda_term_token(&tok)) {
            break;
        }
        token_stream_discard(stream, NULL);
        switch (tok.type) {
        case TOKEN_OPEN_PAREN:
            opand_stack = push_opand(opand_stack, OPAND_OPEN_PAREN);
            break;
        case TOKEN_BACKSLASH:
            opand_stack = push_opand(opand_stack, OPAND_DEF_BEGIN);
            break;
        case TOKEN_CLOSE_PAREN:
        case TOKEN_IDENT:
        case TOKEN_DEFINE:
            break;
        default:
            abort();
        }
    }
}