#include "collection.h"
#include "parse.h"
#include <assert.h>
#include <errno.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char* read_textfile(const char* filename)
{
    FILE* fp = fopen(filename, "r");
    if (!fp) {
        goto couldnt_read_file;
    }

    if (fseek(fp, 0, SEEK_END) != 0) {
        goto couldnt_read_file;
    }

    long file_size = ftell(fp);
    if (file_size < 0) {
        goto couldnt_read_file;
    }

    if (fseek(fp, 0, SEEK_SET) != 0) {
        goto couldnt_read_file;
    }

    char* buffer = malloc(file_size + 1);
    assert(buffer);

    if (fread(buffer, sizeof(char), file_size, fp) != (size_t)file_size) {
        goto couldnt_read_file;
    }

    buffer[file_size] = '\0';
    return buffer;

couldnt_read_file:
    fprintf(stderr,
        "error: couldn't read file '%s': %s\n",
        filename,
        strerror(errno));
    return nullptr;
}

const char* tokty_str(TokTy ty)
{
    switch (ty) {
        case Tok_Eof:
            return "Eof";
        case Tok_Ident:
            return "Ident";
        case Tok_Int:
            return "Int";
        case Tok_Str:
            return "Str";
        case Tok_Char:
            return "Char";
        case Tok_Whitespace:
            return "Whitespace";
        case Tok_HeaderName:
            return "HeaderName";
        case Tok_Eol:
            return "Eol";
        case Tok_Semicolon:
            return "Semicolon";
        case Tok_LParen:
            return "LParen";
        case Tok_RParen:
            return "RParen";
        case Tok_LBrace:
            return "LBrace";
        case Tok_RBrace:
            return "RBrace";
        case Tok_Asterisk:
            return "Asterisk";
        case Tok_Hashtag:
            return "Hashtag";
        default:
            return "<unknown>";
    }
}

void source_iter_init(SourceIter* r, const char* text)
{
    *r = (SourceIter) {
        .text = text,
        .i = 0,
        .line = 1,
        .col = 1,
    };
}

Char source_iter_next(SourceIter* r)
{
    char ch = r->text[r->i];
    Loc loc = { r->line, r->col };

    if (r->text[r->i] != '\0') {
        if (ch == '\n') {
            r->line += 1;
            r->col = 1;
        } else {
            r->col += 1;
        }
        r->i += 1;
    }

    return (Char) { ch, loc };
}

void lsl_iter_init(LslIter* r, SourceIter* source_char_iter)
{
    Char curr = source_iter_next(source_char_iter);

    *r = (LslIter) {
        .source_char_iter = source_char_iter,
        .curr = curr,
    };
}

Char lsl_iter_next(LslIter* r)
{
    Char next = source_iter_next(r->source_char_iter);

    if (r->curr.ch == '\\' && next.ch == '\n') {
        r->curr = source_iter_next(r->source_char_iter);
        return lsl_iter_next(r);
    }

    Char curr = r->curr;
    r->curr = next;
    return curr;
}

void lexer_init(Lexer* r, LslIter* lsl_char_iter, Arena* arena)
{
    Char curr = lsl_iter_next(lsl_char_iter);

    *r = (Lexer) {
        .lsl_iter = lsl_char_iter,
        .arena = arena,
        .curr = curr,
        .lex_whitespace = false,
        .lex_headername = false,
    };
}

static Tok tok(Lexer* l, TokTy ty, const char* text, Loc loc)
{
    char* text_dup = arena_alloc(l->arena, strlen(text) + 1);
    text_dup[0] = '\0';
    strcpy(text_dup, text);

    return (Tok) { ty, text_dup, loc };
}

static bool done(Lexer* l)
{
    return l->curr.ch == '\0';
}

constexpr size_t max_token_text_len = 64;

static void step(Lexer* l, char text[], size_t* text_len)
{
    assert(*text_len < max_token_text_len);
    text[*text_len] = l->curr.ch;
    *text_len += 1;

    l->curr = lsl_iter_next(l->lsl_iter);
}

Tok lexer_next(Lexer* l)
{
    Loc loc = l->curr.loc;

    char text[max_token_text_len] = "";
    size_t text_len = 0;

    if (done(l)) {
        return tok(l, Tok_Eof, text, loc);
    }

    bool matched = false;
    while (strchr(" \t\r", l->curr.ch)) {
        matched = true;
        step(l, text, &text_len);
    }
    if (matched) {
        if (l->lex_whitespace) {
            return tok(l, Tok_Whitespace, text, loc);
        }
        return lexer_next(l);
    }

    while ((l->curr.ch >= 'a' && l->curr.ch <= 'z')
        || (l->curr.ch >= 'A' && l->curr.ch <= 'Z')
        || (matched && l->curr.ch >= '0' && l->curr.ch <= '9')
        || strchr("_", l->curr.ch)) {
        matched = true;
        step(l, text, &text_len);
    }
    if (matched) {
        return tok(l, Tok_Ident, text, loc);
    }

    while ((l->curr.ch >= '1' && l->curr.ch <= '9')
        || (matched && l->curr.ch == '0')) {
        matched = true;
        step(l, text, &text_len);
    }
    if (matched) {
        return tok(l, Tok_Int, text, loc);
    }

    if (l->lex_headername && (l->curr.ch == '"' || l->curr.ch == '<')) {
        char ter = l->curr.ch == '<' ? '>' : '"';
        step(l, text, &text_len);
        while (l->curr.ch != '\0' && l->curr.ch != '\n' && l->curr.ch != ter) {
            step(l, text, &text_len);
        }
        if (l->curr.ch != ter) {
            fprintf(stderr,
                "error: malformed header name, expected '%c' on line %d\n",
                ter,
                l->curr.loc.line);
            return lexer_next(l);
        }
        step(l, text, &text_len);
        return tok(l, Tok_HeaderName, text, loc);
    }

    if (l->curr.ch == '"') {
        step(l, text, &text_len);
        while (l->curr.ch != '"') {
            if (l->curr.ch == '\\') {
                step(l, text, &text_len);
                if (done(l))
                    break;
            }
            step(l, text, &text_len);
        }
        if (done(l) || l->curr.ch != '"') {
            fprintf(stderr,
                "error: malformed string literal on line %d\n",
                l->curr.loc.line);
            return lexer_next(l);
        }
        step(l, text, &text_len);
        return tok(l, Tok_Str, text, loc);
    }

    if (l->curr.ch == '\'') {
        step(l, text, &text_len);
        if (l->curr.ch == '\\') {
            step(l, text, &text_len);
        }
        if (!done(l)) {
            step(l, text, &text_len);
        }
        if (done(l) && l->curr.ch != '\'') {
            fprintf(stderr,
                "error: malformed character literal on line %d\n",
                l->curr.loc.line);
            return lexer_next(l);
        }
        step(l, text, &text_len);
        return tok(l, Tok_Char, text, loc);
    }

    if (strchr("\n;(){},*#", l->curr.ch)) {
        TokTy ty = (TokTy)l->curr.ch;
        step(l, text, &text_len);
        return tok(l, ty, text, loc);
    }
    fprintf(stderr,
        "error: illegal character '%c' on line %d\n",
        l->curr.ch,
        l->curr.loc.line);
    step(l, text, &text_len);
    return lexer_next(l);
}