#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdbool.h>
#include <string.h>

typedef struct {
    enum lapis_ttype {
        LAPIS_TTYPE_NONE,
        LAPIS_TTYPE_IDENT,
        LAPIS_TTYPE_STR,
        LAPIS_TTYPE_FLOAT,
        LAPIS_TTYPE_INT,
        LAPIS_TTYPE_BOOL,
        LAPIS_TTYPE_OPER,
    } type;

    union {
        struct {
            size_t len;
            char * str;
        };
        double f64;
        int64_t i64;
        _Bool bool_;
    };
} lapis_token_t;

typedef struct lapis_node_s {
    lapis_token_t value;
    size_t lhs_idx, rhs_idx;
} lapis_node_t;

void lapis_node_print(const lapis_node_t *nodes, size_t idx) {

    if ( nodes[idx].value.type == LAPIS_TTYPE_OPER ) putchar('(');

    if ( nodes[idx].lhs_idx != SIZE_MAX ) {
        lapis_node_print(nodes, nodes[idx].lhs_idx);
        putchar(' ');
    }

    switch (nodes[idx].value.type){
        default: break;
        case LAPIS_TTYPE_IDENT:
        case LAPIS_TTYPE_STR:
        case LAPIS_TTYPE_OPER:
            fwrite(nodes[idx].value.str, 1, nodes[idx].value.len, stdout);
            break;
        case LAPIS_TTYPE_FLOAT:
            printf("%lf", nodes[idx].value.f64);
            break;
        case LAPIS_TTYPE_INT:
            printf("%ld", nodes[idx].value.i64);
            break;
    }

    if ( nodes[idx].rhs_idx != SIZE_MAX ) {
        putchar(' ');
        lapis_node_print(nodes, nodes[idx].rhs_idx);
    }

    if ( nodes[idx].value.type == LAPIS_TTYPE_OPER ) putchar(')');
}

/// Free a token's internal buffer if it has one
void lapis_token_free(lapis_token_t *token) {
    if ( token->type == LAPIS_TTYPE_IDENT || token->type == LAPIS_TTYPE_OPER ) {
        if ( token->str != NULL ) {
            free( token->str );
            token->str = NULL;
            token->len = 0;
        }
    }
}

lapis_token_t *lapis_parse_tokens(size_t *ntokens, FILE *f) {

    size_t num_tokens = 0;
    lapis_token_t *tokens = NULL;
    lapis_token_t tmptok = { .type = LAPIS_TTYPE_NONE, .str = NULL, .len = 0 };

    _Bool end_of_expression = false;

    int c;
    while ( (c = fgetc(f)) != EOF && !end_of_expression ) {

        _Bool in_escape = false;

        // skip over comments
        if ( c == '#' ) {
            while ( (c = fgetc(f)) != '\n' && c != EOF );
            if ( c == EOF ) break;
        }

        // detect line escapes
        if ( c == '\\' ) {
            in_escape = true;
            c = fgetc(f);
            if ( c == EOF ) break;
        }

        if ( c == ';' || (!in_escape && c == '\n') ) {
            c = ' ';
            if ( num_tokens ) end_of_expression = true;
        }

        enum lapis_ttype cur_ttype;

        if ( (tmptok.type == LAPIS_TTYPE_IDENT && isdigit(c)) || isalpha(c) || c == '_' ) {
            cur_ttype = LAPIS_TTYPE_IDENT;
        } else if ( isdigit(c) ) {
            cur_ttype = LAPIS_TTYPE_INT;
        } else if ( c == '"' ) {
            cur_ttype = LAPIS_TTYPE_STR;
        } else if ( ispunct(c) ) {
            cur_ttype = LAPIS_TTYPE_OPER;
        } else if ( isspace(c) ) {
            cur_ttype = LAPIS_TTYPE_NONE;
        } else {
            fprintf(stderr, "ERROR [%s]: Invalid char c='%c' at offset=%ld!\n", __func__, c, ftell(f));
            goto ERROR;
        }

        if ( cur_ttype != tmptok.type ) {
            // store the previous token if it was valid
            if ( tmptok.type != LAPIS_TTYPE_NONE ) {
                tokens = realloc(tokens, (num_tokens + 1) * sizeof(lapis_token_t));
                if ( tokens == NULL ) {
                    fprintf(stderr, "ERROR [%s:%d]: realloc failed!\n", __func__, __LINE__);
                    goto ERROR;
                }
                tokens[num_tokens] = tmptok;
                num_tokens++;
            }

            // initialize new token
            tmptok.type = cur_ttype;
            switch (cur_ttype) {
                default: break;
                case LAPIS_TTYPE_IDENT:
                case LAPIS_TTYPE_OPER:
                case LAPIS_TTYPE_STR:
                    tmptok.str = NULL;
                    tmptok.len = 0;
                    break;
                // NOTE: float and bool will not occur during initial tokenization
                // they are only for results of reducing expressions later
                //case LAPIS_TTYPE_FLOAT: tmptok.f64 = 0.; break;
                //case LAPIS_TTYPE_BOOL:  tmptok.bool_ = false; break;
                case LAPIS_TTYPE_INT:   tmptok.i64 = 0l; break;
            }
        }

        if ( cur_ttype == LAPIS_TTYPE_STR ) {
            _Bool in_esc = false;
            while ( (c = fgetc(f)) != '"' || in_esc ) {
                if ( c == EOF ) {
                    fprintf(stderr, "ERROR [%s]: EOF inside string token! offset=%ld\n", __func__, ftell(f));
                    goto ERROR;
                }
                if ( !in_esc && c == '\\' ) {
                    in_esc = true;
                    continue;
                } else {
                    in_esc = false;
                }
                tmptok.str = realloc(tmptok.str, tmptok.len + 1);
                if ( tmptok.str == NULL ) {
                    fprintf(stderr, "ERROR [%s:%d]: realloc failed!\n", __func__, __LINE__);
                    goto ERROR;
                }
                tmptok.str[tmptok.len] = c;
                tmptok.len++;
            }
            continue;
        }

        // extend existing token
        switch (cur_ttype) {
            default: break;
            case LAPIS_TTYPE_IDENT:
            case LAPIS_TTYPE_OPER:
                tmptok.str = realloc(tmptok.str, tmptok.len + 1);
                if ( tmptok.str == NULL ) {
                    fprintf(stderr, "ERROR [%s:%d]: realloc failed!\n", __func__, __LINE__);
                    goto ERROR;
                }
                tmptok.str[tmptok.len] = c;
                tmptok.len++;
                break;
            case LAPIS_TTYPE_INT:
                tmptok.i64 *= 10;
                tmptok.i64 += (c - '0');
                break;
        }
    }

    // handle float decimal point
    // FIXME known bug if '.' occurs after an operator w/o a space (e.g. +.234234 fails to parse as a float)
    for (size_t n=1; n < num_tokens; n++) {

        if ( tokens[n].type == LAPIS_TTYPE_OPER && tokens[n].len == 1 && tokens[n].str[0] == '.' ) {

            _Bool  valid = false;
            double val = 0.;

            if ( tokens[n-1].type == LAPIS_TTYPE_INT ) {
                val += tokens[n-1].i64;
                tokens[n-1].type = LAPIS_TTYPE_NONE;
                valid = true;
            }

            if ( n+1 < num_tokens && tokens[n+1].type == LAPIS_TTYPE_INT ) {
                double den = 1;
                while ( den < tokens[n+1].i64 ) den *= 10;
                val += tokens[n+1].i64 / den;
                tokens[n+1].type = LAPIS_TTYPE_NONE;
                valid = true;
            }

            if ( !valid ) continue;

            tokens[n].type = LAPIS_TTYPE_FLOAT;
            tokens[n].f64  = val;
        }
    }

    // TODO handle sci notation (e.g. 3e[+-]6,3E[+-]6,...)

    *ntokens = num_tokens;
    return tokens;
ERROR:
    if ( tokens ) {
        for (size_t n=0; n < num_tokens; n++) lapis_token_free(&tokens[n]);
        free(tokens);
    }
    return NULL;
}

void lapis_parse(FILE *f) {

    size_t ntokens=0;
    lapis_token_t *tokens = lapis_parse_tokens(&ntokens, stdin);
    if ( tokens == NULL ) return;

    int64_t *oper_priorities = malloc( ntokens * sizeof(int64_t) );
    if ( oper_priorities == NULL ) return;

    // 0 - no args, 1 - lhs, 2 - rhs, 3 - both
    uint8_t *oper_arg_form = malloc( ntokens * sizeof(uint8_t) );
    if ( oper_arg_form == NULL ) return;

    memset(oper_arg_form, 0, ntokens);

    int64_t paren_level = 0;

    for (size_t n=0; n < ntokens; n++) {

        if ( tokens[n].type != LAPIS_TTYPE_OPER ) {
            oper_priorities[n] = -1;
            continue;
        }

        int64_t prod=1;
        for (size_t k=0; k < tokens[n].len; k++) prod *= tokens[n].str[k];

        switch (prod) {
            default:
                fputs("ERROR: unknown priority for operator '", stderr);
                fwrite(tokens[n].str, 1, tokens[n].len, stderr);
                fputs("'\n", stderr);
                return;
            case 1ul*',':
                oper_priorities[n] = 1;
                oper_arg_form[n] = 3;
                break;
            case 1ul*'=':
            case 1ul*'+'*'=':
            case 1ul*'-'*'=':
            case 1ul*'*'*'=':
            case 1ul*'/'*'=':
            case 1ul*'%'*'=':
            case 1ul*'<'*'<'*'=':
            case 1ul*'>'*'>'*'=':
            case 1ul*'&'*'=':
            case 1ul*'^'*'=':
            case 1ul*'|'*'=':
                oper_priorities[n] = 2;
                oper_arg_form[n] = 3;
                break;
                //?: (3)
            case 1ul*'|'*'|': oper_priorities[n] = 4; oper_arg_form[n] = 3; break;
            case 1ul*'&'*'&': oper_priorities[n] = 5; oper_arg_form[n] = 3; break;
            case 1ul*'|':     oper_priorities[n] = 6; oper_arg_form[n] = 3; break;
            case 1ul*'^':     oper_priorities[n] = 7; oper_arg_form[n] = 3; break;
            case 1ul*'&':     oper_priorities[n] = 8; oper_arg_form[n] = 3; break;
            case 1ul*'='*'=':
            case 1ul*'!'*'=':
                oper_priorities[n] = 9;
                oper_arg_form[n] = 3;
                break;
            case 1ul*'<':
            case 1ul*'>':
            case 1ul*'<'*'=':
            case 1ul*'>'*'=':
                oper_priorities[n] = 10;
                oper_arg_form[n] = 3;
                break;
            case 1ul*'<'*'<':
            case 1ul*'>'*'>':
                oper_priorities[n] = 11;
                oper_arg_form[n] = 3;
                break;
            case 1ul*'+':
            case 1ul*'-':
                // check if actual binary operator or if this is a sign
                if ( n > 0 && tokens[n-1].type == LAPIS_TTYPE_OPER ) {
                    oper_arg_form[n] = 2; /*rhs only*/
                    oper_priorities[n] = 14;
                } else {
                    oper_arg_form[n] = 3; /*binary*/
                    oper_priorities[n] = 12;
                }
                break;
            case 1ul*'*':
            case 1ul*'/':
            case 1ul*'%':
                oper_priorities[n] = 13;
                oper_arg_form[n] = 3;
                break;
            case 1ul*':':
                oper_priorities[n] = 14;
                oper_arg_form[n] = 3;
                break;
            case 1ul*'!':
            case 1ul*'~':
                oper_priorities[n] = 14;
                oper_arg_form[n] = 2;/*rhs only*/
                break;
            case 1ul*'+'*'+':
            case 1ul*'-'*'-':
                oper_priorities[n] = 15;
                oper_arg_form[n] = 3;
                break;
            case 1ul*'.':
            case 1ul*'-'*'>':
                oper_priorities[n] = 15;
                oper_arg_form[n] = 3;
                break;
            case 1ul*'(':
                // handle function call / keyword operator
                if ( n > 0 && tokens[n-1].type == LAPIS_TTYPE_IDENT ) {
                    // treat the function identifier as a prefix operator
                    tokens[n-1].type = LAPIS_TTYPE_OPER;
                    oper_priorities[n-1] = 15 + paren_level * 16;
                    oper_arg_form[n-1] = 2; // prefix-unary; takes only rhs
                }
                // clear the '(' as being an operator
                oper_priorities[n] = -1;
                tokens[n].type = LAPIS_TTYPE_NONE;
                paren_level++;
                break;
            case 1ul*')':
                if ( paren_level == 0 ) {
                    fprintf(stderr, "ERROR(%d): unexpected ')'\n", __LINE__);
                    return;
                }
                // clear the ')' as being an operator
                oper_priorities[n] = -1;
                tokens[n].type = LAPIS_TTYPE_NONE;
                paren_level--;
                break;
        }

        if ( oper_priorities[n] != -1 ) oper_priorities[n] += paren_level * 16;
    }

    size_t nnodes = 0;
    lapis_node_t *nodes = NULL;

#define ADD_NODE(NODE) \
    (nnodes++, nodes = realloc(nodes, nnodes * sizeof(lapis_node_t)), nodes[nnodes-1] = NODE)

    while (1) {

        // seek the next highest priority operator

        int64_t max_prior = -1;
        size_t  max_prior_idx = SIZE_MAX;

        for (size_t n=0; n < ntokens; n++) {

            if ( oper_priorities[n] < 0 ) continue;

            if ( oper_priorities[n] > max_prior ) {
                max_prior = oper_priorities[n];
                max_prior_idx = n;
            }
        }

        // quit if no more operators were found

        if ( max_prior_idx == SIZE_MAX ) break;

        lapis_node_t node = {
            .value = tokens[max_prior_idx],
            .lhs_idx = SIZE_MAX,
            .rhs_idx = SIZE_MAX
        };

        size_t update_lhs_idx = SIZE_MAX, update_rhs_idx = SIZE_MAX;

        if ( oper_arg_form[max_prior_idx] & 1 ) { /*get lhs if needed*/

            size_t n = max_prior_idx;
            while ( n > 0 ) {
                n--;
                if ( tokens[n].type != LAPIS_TTYPE_NONE ) break;
            }

            if ( n == max_prior_idx || tokens[n].type == LAPIS_TTYPE_NONE ) {
                printf("ERROR: bad logic line #%d\n", __LINE__);
                return;
            }

            if ( tokens[n].type == LAPIS_TTYPE_OPER ) {
            
                if ( oper_priorities[n] >= -1 ) {
                    printf("ERROR: bad logic line #%d\n", __LINE__);
                    return;
                }

                // This is very weird, BUT as a vile hack I encode the node index
                // into the negative values of oper_priorities to simultaneously:
                // a) clear the priority so the next one can be found
                // b) store the index of the new node associated with the operator so
                // later lower priority dependent operators can find its node.
                int64_t node_idx = -(oper_priorities[n] + 2);

                if ( node_idx < 0 ) {
                    printf("ERROR: bad logic line #%d\n", __LINE__);
                    return;
                }

                node.lhs_idx = node_idx;

                // since we are taking ownership of this node we must flag it for update
                update_lhs_idx = n;

            } else {

                lapis_node_t tmpnode = {
                    .value = tokens[n],
                    .lhs_idx = SIZE_MAX,
                    .rhs_idx = SIZE_MAX
                };

                ADD_NODE( tmpnode );
                node.lhs_idx = nnodes-1;
            }

            // clear token type to prevent reuse
            tokens[n].type = LAPIS_TTYPE_NONE;
        }

        if ( oper_arg_form[max_prior_idx] & 2 ) { /*get rhs if needed*/

            size_t n = max_prior_idx;
            for (; n < ntokens; n++) {
                if ( n == max_prior_idx ) continue;
                if ( tokens[n].type != LAPIS_TTYPE_NONE ) break;
            }

            if ( n == max_prior_idx || tokens[n].type == LAPIS_TTYPE_NONE ) {
                printf("ERROR: bad logic line #%d\n", __LINE__);
                return;
            }

            if ( tokens[n].type == LAPIS_TTYPE_OPER ) {
            
                if ( oper_priorities[n] >= -1 ) {
                    printf("ERROR: bad logic line #%d\n", __LINE__);
                    return;
                }

                // This is very weird, BUT as a vile hack I encode the node index
                // into the negative values of oper_priorities to simultaneously:
                // a) clear the priority so the next one can be found
                // b) store the index of the new node associated with the operator so
                // later lower priority dependent operators can find its node.
                int64_t node_idx = -(oper_priorities[n] + 2);

                if ( node_idx < 0 ) {
                    printf("ERROR: bad logic line #%d\n", __LINE__);
                    return;
                }

                node.rhs_idx = node_idx;

                // since we are taking ownership of this node we must flag it for update
                update_rhs_idx = n;

            } else {

                lapis_node_t tmpnode = {
                    .value = tokens[n],
                    .lhs_idx = SIZE_MAX,
                    .rhs_idx = SIZE_MAX
                };

                ADD_NODE( tmpnode );
                node.rhs_idx = nnodes-1;
            }

            // clear token type to prevent reuse
            tokens[n].type = LAPIS_TTYPE_NONE;
        }

        ADD_NODE( node );
        int64_t idx = nnodes - 1;

        printf("add oper token %lu w/ priority %ld as node %ld\n",
            max_prior_idx, oper_priorities[max_prior_idx], idx);

        // vile hack again, but on the setting side (see previous comment)
        oper_priorities[max_prior_idx] = -idx - 2;

        // We also have to update any previous operator nodes to point to our new
        // node as well. This is because those nodes will end up double owned otherwise.
        if ( update_lhs_idx != SIZE_MAX ) oper_priorities[update_lhs_idx] = -idx - 2;
        if ( update_rhs_idx != SIZE_MAX ) oper_priorities[update_rhs_idx] = -idx - 2;
    }

    //TODO cleanup allocs, error handling, ';' or w/e to **separate expressions**

    lapis_node_print(nodes, nnodes-1);
    putchar('\n');
}

int main() {
#if 0
    size_t ntokens=0;
    lapis_token_t *tokens = lapis_parse_tokens(&ntokens, stdin);

    printf("Tokens (%lu):\n", ntokens);
    for (size_t n=0; n < ntokens; n++) {
        switch (tokens[n].type) {
            default: break;
            case LAPIS_TTYPE_STR:
            case LAPIS_TTYPE_IDENT:
            case LAPIS_TTYPE_OPER:
                fputs("  ", stdout);
                fwrite(tokens[n].str, 1, tokens[n].len, stdout);
                putchar('\n');
                break;
            case LAPIS_TTYPE_INT:
                printf("  %ld (int)\n", tokens[n].i64);
                break;
            case LAPIS_TTYPE_FLOAT:
                printf("  %lf (float)\n", tokens[n].f64);
                break;
        }
    }
#else
    lapis_parse(stdin);
#endif

    return 0;
}