#include <stdio.h>
#include <ctype.h>

#include "shorthand.h"

typedef struct StringView {
    char *start;
    size_t n;
} StringView;

void
sv_write(StringView sv) {
    for (size_t i = 0; i < sv.n; i++) {
        putchar(sv.start[i]);
    }
}

StringView
read_line(void) {
    #define RL_BUF_SIZE 1024
    static char readline_buf[RL_BUF_SIZE];

    // Clear buffer.
    for (size_t i = 0; i < RL_BUF_SIZE; i++) {
        readline_buf[i] = 0;
    }

    // Barebones readline implementation.
    size_t n = 0;
    char c;
    while ((c = getchar()) != '\n') {
        if (c == '\b') {
            readline_buf[n] = '\0';
            n--;
        } else if (((u8)c >= 0x20 && (u8)c <= 0x7F) && n < RL_BUF_SIZE) {
            readline_buf[n] = c;
            n++;
        }
    }

    return (StringView){.start = (char *)&readline_buf, .n = n};
}

typedef struct Tokens {
    StringView *start;
    size_t n;
} Tokens;

Tokens
tokenize(StringView sv) {
    // NOTE: Not allocating any memory for now, but we are limited by a maximum
    // number of tokens we can process.
    #define TOKENS_BUF_SIZE 1024
    static StringView tokens_buf[TOKENS_BUF_SIZE];

    // Clear buffer.
    for (size_t i = 0; i < TOKENS_BUF_SIZE; i++) {
        tokens_buf[i] = (StringView){0};
    }

    size_t n = 0;
    size_t token_n = 0;
    for (size_t i = 0; i < sv.n; i++) {
        switch (sv.start[i]) {
            case ' ':
            case '\f':
            case '\n':
            case '\r':
            case '\t':
            case '\v': {
                if (token_n != 0) {
                    // Push token.
                    tokens_buf[n++] = (StringView){
                        .start = &sv.start[i - token_n],
                        .n = token_n,
                    };
                    token_n = 0;
                }
                continue;
            } break;
            case '(': {
                if ((i + 1 < sv.n)) {
                    char next_c = sv.start[i + 1];
                    if (isspace(next_c)) {
                        fprintf(stderr, "error: lparen delimiter followed by space\n");
                        return (Tokens){0};
                    }
                }

                if (token_n != 0) {
                    fprintf(stderr, "error: lparen delimiter within symbol name\n");
                    return (Tokens){0};
                }
                // Push paren token.
                tokens_buf[n++] = (StringView){
                    .start = &sv.start[i],
                    .n = 1,
                };
            } break;
            case ')': {
                if ((i + 1 < sv.n)) {
                    char next_c = sv.start[i + 1];
                    if ((next_c != ')' && !isspace(next_c))) {
                        fprintf(stderr, "error: rparen delimiter within symbol name\n");
                        return (Tokens){0};
                    }
                }

                if (token_n != 0) {
                    // Push previous token.
                    tokens_buf[n++] = (StringView){
                        .start = &sv.start[i - token_n],
                        .n = token_n,
                    };
                    token_n = 0;
                }

                // Push paren token.
                tokens_buf[n++] = (StringView){
                    .start = &sv.start[i],
                    .n = 1,
                };
            } break;
            default: {
                token_n++;
            } break;
        }
    }
    if (token_n != 0) {
        // End of line encountered.
        tokens_buf[n++] = (StringView){
            .start = &sv.start[sv.n - token_n],
            .n = token_n,
        };
    }

    // DEBUG: Printing tokens.
    printf("N_TOKENS: %ld\n", n);
    for (size_t i = 0; i < n; i++) {
        printf("TOKEN: ");
        sv_write(tokens_buf[i]);
        printf("\tN: %ld", tokens_buf[i].n);
        printf("\n");
    }

    return (Tokens){.start = (StringView *)&tokens_buf, .n = n};
}

void
display(StringView sv) {
    if (sv.n != 0) {
        sv_write(sv);
        printf("\n");
    }
}

#define REPL_PROMPT "bdl> "

int
main(void) {
    printf("BDL REPL (Press Ctrl-C to exit)\n");
    while (true) {
        printf(REPL_PROMPT);
        StringView line = read_line();
        tokenize(line);
        display(line);
    }
    return 0;
}