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path: root/src/template.c
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#include <stdio.h>
#include <stdlib.h>
#include <err.h>
#include <unistd.h>
#include <dirent.h>
#include <string.h>
#include <assert.h>

#include "vendor/mpc.h"
#include "template.h"

enum unja_object_type {
    OBJ_NULL,
    OBJ_INT,
    OBJ_STRING,
};

struct unja_object {
    enum unja_object_type type;
    int integer;
    char *string;
    char *string_ptr;
};

struct unja_object null_object = { 
    .type = OBJ_NULL,
};

struct buffer {
    int size;
    int cap;
    char *string;
};

struct env {
    struct hashmap *templates;
};

struct template {
    char *name;
    mpc_ast_t *ast;
    struct hashmap *blocks;
    char *parent;
};

/* ensure buffer has room for a string sized l, grows buffer capacity if needed */
void buffer_reserve(struct buffer *buf, int l) {
    int req_size = buf->size + l;
    if (req_size >= buf->cap) {
        while (req_size >= buf->cap) {
            buf->cap *= 2;
        }
        
        buf->string = realloc(buf->string, buf->cap * sizeof *buf->string);
        if (!buf->string) {
            errx(EXIT_FAILURE, "out of memory");
        }
    }
}


mpc_parser_t *parser_init() {
    static mpc_parser_t *template;
    if (template != NULL) {
        return template;
    }

    mpc_parser_t *spaces = mpc_new("spaces");
    mpc_parser_t *symbol = mpc_new("symbol");
    mpc_parser_t *number = mpc_new("number");
    mpc_parser_t *string = mpc_new("string");
    mpc_parser_t *text = mpc_new("text");
    mpc_parser_t *print = mpc_new("print");
    mpc_parser_t *lexp = mpc_new("lexp");
    mpc_parser_t *exp = mpc_new("expression");
    mpc_parser_t *comment = mpc_new("comment");
    mpc_parser_t *statement = mpc_new("statement");
    mpc_parser_t *statement_open = mpc_new("statement_open");
    mpc_parser_t *statement_close = mpc_new("statement_close");
    mpc_parser_t *statement_for = mpc_new("for");
    mpc_parser_t *statement_if = mpc_new("if");
    mpc_parser_t *statement_block = mpc_new("block");
    mpc_parser_t *statement_extends = mpc_new("extends");
    mpc_parser_t *body = mpc_new("body");
    mpc_parser_t *content = mpc_new("content");
    mpc_parser_t *factor = mpc_new("factor");
    mpc_parser_t *term = mpc_new("term");
    mpc_parser_t *filter = mpc_new("filter");

    template = mpc_new("template");
    mpca_lang(MPCA_LANG_WHITESPACE_SENSITIVE,
        " spaces    : / */ ;"
        " symbol    : /[a-zA-Z][a-zA-Z0-9_.]*/ ;"
        " number    : /[0-9]+/ ;"
        " text      : /[^{][^{%#]*/;"
        " string    : '\"' /([^\"])*/ '\"' ;"
        " factor    : <symbol> | <number> | <string> ;"
        " filter    : <spaces> '|' <spaces> <symbol>; "
        " term      :  <factor> (<spaces> ('*' | '/' | '%') <spaces> <factor>)* <filter>?;"
        " lexp      : <term> (<spaces> ('+' | '-') <spaces> <term>)* ;"
        " expression: <lexp> <spaces> '>' <spaces> <lexp> "
        "           | <lexp> <spaces> '<' <spaces> <lexp> "
        "           | <lexp> <spaces> \">=\" <spaces> <lexp> "
        "           | <lexp> <spaces> \"<=\" <spaces> <lexp> "
        "           | <lexp> <spaces> \"!=\" <spaces> <lexp> "
        "           | <lexp> <spaces> \"==\" <spaces> <lexp> "
        "           | \"not\" <spaces> <lexp> "
        "           | <lexp> ;"
        " print     : /{{2}-? */ <expression> / *-?}}/ ;"
        " comment   : \"{#\" /[^#][^#}]*/ \"#}\" ;"
        " statement_open: /{\%-? */;"
        " statement_close: / *-?\%}/;"
        " for       : <statement_open> \"for \" <symbol> \" in \" <symbol> <statement_close> <body> <statement_open> \"endfor\" <statement_close> ;"
        " block     : <statement_open> \"block \" <symbol> <statement_close> <body> <statement_open> \"endblock\" <statement_close>;"
        " extends   : <statement_open> \"extends \" <string> <statement_close>;"
        " if        : <statement_open> \"if \" <expression> <statement_close> <body> (<statement_open> \"else\" <statement_close> <body>)? <statement_open> \"endif\" <statement_close> ;"
        " statement : <for> | <block> | <extends> | <if> ;"
        " content   : <print> | <statement> | <text> | <comment>;"
        " body      : <content>* ;"
        " template  : /^/ <body> /$/ ;",
        spaces,
        filter,
        factor, 
        term,
        symbol, 
        text,
        number,
        string,
        print,
        lexp,
        exp, 
        comment,
        statement_open, 
        statement_close, 
        statement,
        statement_if,
        statement_for, 
        statement_block,
        statement_extends,
        content, 
        body, 
        template);

    return template;
}

mpc_ast_t *parse(char *tmpl) {
    mpc_parser_t *parser = parser_init();
    mpc_result_t r;

    if (!mpc_parse("input", tmpl, parser, &r)) {
        puts(tmpl);
        mpc_err_print(r.error);
        mpc_err_delete(r.error);
        return NULL;
    }

    return r.output;
}

struct hashmap *find_blocks_in_ast(mpc_ast_t *node, struct hashmap *map) {
    if (strstr(node->tag, "content|statement|block")) {
        char *name = node->children[2]->contents;
        hashmap_insert(map, name, node);
    }

    for (int i=0; i < node->children_num; i++) {
        find_blocks_in_ast(node->children[i], map);
    }

    return map;
}

struct env *env_new(char *dirname) {
    /* store current working dir so we can revert to it after reading templates */
    char working_dir[256];
    getcwd(working_dir, 255);

    DIR *dr = opendir(dirname); 
    if (dr == NULL) { 
        errx(EXIT_FAILURE, "could not open directory \"%s\"", dirname); 
    } 
  
    struct env *env = malloc(sizeof *env);
    env->templates = hashmap_new();
    chdir(dirname);

    struct dirent *de;   
    while ((de = readdir(dr)) != NULL) {
        // skip files starting with a dot
        if (de->d_name[0] == '.') {
            continue;
        }

        // copy template name as closedir free's it otherwise
        char *name = malloc(strlen(de->d_name) + 1);
        strcpy(name, de->d_name);

        char *tmpl = read_file(name);
        mpc_ast_t *ast = parse(tmpl);
        free(tmpl);

        struct template *t = malloc(sizeof *t);
        t->ast = ast;
        t->name = name;
        t->blocks = find_blocks_in_ast(ast, hashmap_new());
        t->parent = NULL;

        if (ast->children_num > 1 && ast->children[1]->children_num > 0 && strstr(ast->children[1]->children[0]->tag, "content|statement|extends")) {
            t->parent = ast->children[1]->children[0]->children[2]->children[1]->contents;
        }

        hashmap_insert(env->templates, name, t);
    }
  
    closedir(dr); 
    chdir(working_dir);    
    return env;
}

void template_free(void *v) {
    struct template *t = (struct template *)v;
    hashmap_free(t->blocks);
    mpc_ast_delete(t->ast);
    free(t->name);
    free(t);
}

void env_free(struct env *env) {
    hashmap_walk(env->templates, template_free);
    hashmap_free(env->templates);
    free(env);
}

char *read_file(char *filename) {
    char *input = malloc(BUFSIZ);
    unsigned int size = 0;

    FILE *f = fopen(filename, "r");
    if (!f) {
        errx(EXIT_FAILURE, "could not open \"%s\" for reading", filename);
    }

    unsigned int read = 0;
    while ( (read = fread(input, 1, BUFSIZ, f)) > 0) {
        size += read;
        input = realloc(input, size + BUFSIZ);
    }

    fclose(f);

    input[size] = '\0';
    return input;
}

char *trim_trailing_whitespace(char *str) {
    for (int i=strlen(str)-1; i >= 0 && isspace(str[i]); i--) {
        str[i] = '\0';
    }
    return str;
}

char *trim_leading_whitespace(char *str) {
    while (isspace(*str)) {
        str++;
    }

    return str;
}

struct unja_object *make_string_object(char *value, char *value2) {
    struct unja_object *obj = malloc(sizeof *obj);
    obj->type = OBJ_STRING;
    int l = strlen(value) + 1;
    if (value2) {
        l += strlen(value2);
    }

   
    obj->string = malloc(l);
    obj->string_ptr = obj->string;
    strcpy(obj->string, value);
    
    if(value2) {
        strcat(obj->string, value2);
    }
    return obj;
}

struct unja_object *make_int_object(int value) {
    struct unja_object *obj = malloc(sizeof *obj);
    obj->type = OBJ_INT;
    obj->integer = value;
    return obj;
}


void eval_object(struct buffer *buf, struct unja_object *obj) {
    char tmp[64];

    switch (obj->type) {
        case OBJ_NULL: 
            break;
        case OBJ_STRING:
            buffer_reserve(buf, strlen(obj->string));
            strcat(buf->string, obj->string);
            break;
        case OBJ_INT: 
            sprintf(tmp, "%d", obj->integer);
            buffer_reserve(buf, strlen(tmp));
            strcat(buf->string, tmp);
            break;
    }
}

int object_to_int(struct unja_object *obj) {
     switch (obj->type) {
        case OBJ_NULL: return 0; 
        case OBJ_STRING: return atoi(obj->string);
        case OBJ_INT: return obj->integer;
    }

    return 0;
}

void object_free(struct unja_object *obj) {
    switch(obj->type) {
        case OBJ_NULL: return;
        case OBJ_STRING: 
            free(obj->string_ptr);
        break;
        case OBJ_INT: break;
    }

    free(obj);
}

int object_is_truthy(struct unja_object *obj) {
    switch (obj->type) {
        case OBJ_NULL: return 0; 
        case OBJ_STRING: return strlen(obj->string) > 0 && strcmp(obj->string, "0") != 0;
        case OBJ_INT: return obj->integer > 0;
    }

    return 0;
}

struct context {
    struct hashmap *vars;
    struct hashmap *filters;
    struct env *env;
    struct template *current_template;
};

struct unja_object *eval_expression_value(mpc_ast_t* node, struct context *ctx) {
    if (strstr(node->tag, "symbol|")) {
        /* Return empty string if no vars were passed. Should probably signal error here. */
        if (ctx->vars == NULL) {
           return &null_object;
        }

        char *key = node->contents;
        char *value = hashmap_resolve(ctx->vars, key);

        /* TODO: Handle unexisting symbols (returns NULL currently) */
        if (value == NULL) {
            return &null_object;
        }

        return make_string_object(value, NULL);
    } else if(strstr(node->tag, "number|")) {
        return make_int_object(atoi(node->contents));
    } else if(strstr(node->tag, "string|")) {
        return make_string_object(node->children[1]->contents, NULL);
    }

    return &null_object;
}

struct unja_object *eval_string_infix_expression(struct unja_object *left, char *op, struct unja_object *right) {
    struct unja_object *result;

    if (strcmp(op, "+") == 0) {
        result = make_string_object(left->string, right->string);
    } else if (strcmp(op, "==") == 0) {
        result = make_int_object(strcmp(left->string, right->string) == 0);
    } else if(strcmp(op, "!=") == 0) {
        result = make_int_object(strcmp(left->string, right->string) != 0);
    } else {
        errx(EXIT_FAILURE, "invalid string operator: %s", op);
    }

    object_free(left);
    object_free(right);
    return result;
}

struct unja_object *eval_infix_expression(struct unja_object *left, char *op, struct unja_object *right) {
    /* if operator is + and either left or right node is of type string: concat */
    if (left->type == OBJ_STRING && right->type == OBJ_STRING) {           
        return eval_string_infix_expression(left, op, right);
    } 

    int result;
    switch (op[0]) {
        case '+': result = object_to_int(left) + object_to_int(right); break;
        case '-': result = object_to_int(left) - object_to_int(right); break;
        case '/': result = object_to_int(left) / object_to_int(right); break;
        case '*': result = object_to_int(left) * object_to_int(right); break;
        case '%': result = object_to_int(left) % object_to_int(right); break;
        case '>': 
            if (op[1] == '=') {
                result = object_to_int(left) >= object_to_int(right);    
            } else {
                result = object_to_int(left) > object_to_int(right); 
            }
            break;
        case '<': 
            if (op[1] == '=') {
                result = object_to_int(left) <= object_to_int(right);    
            } else {
                result = object_to_int(left) < object_to_int(right); 
            }
            break;
        case '!': 
            if (op[1] == '=') {
                result = object_to_int(left) != object_to_int(right);    
            }
            break;
        case '=': 
            if (op[1] == '=') {
                result = object_to_int(left) == object_to_int(right);    
            }
            break;
    }

    object_free(left);
    object_free(right);
    return make_int_object(result);
}

struct unja_object *eval_expression(mpc_ast_t* expr, struct context *ctx) {

    /* singular term */
    if (expr->children_num == 0 || strstr(expr->tag, "string|")) {
        return eval_expression_value(expr, ctx);
    }

    struct unja_object *result;

    /* singular negated term */
    if (strcmp(expr->children[0]->contents, "not") == 0) {
        result = eval_expression_value(expr->children[2], ctx);
        struct unja_object *negated = make_int_object(!object_to_int(result));
        object_free(result);
        return negated;
    }

    /* otherwise: with operator */
    unsigned int offset = 0; 
    mpc_ast_t *left_node = expr->children[0];
    struct unja_object *left = eval_expression(left_node, ctx);
    result = left;

    while (offset < (expr->children_num - 1)) {
        /* Check if we arrived at a filter (guaranteed to be last in expression list) */
        if (strstr(expr->children[offset+1]->tag, "filter")) {
            char *filter_name = expr->children[offset+1]->children[3]->contents;
            struct unja_object *(*filter_fn)(struct unja_object *) = hashmap_get(ctx->filters, filter_name);
            if (NULL == filter_fn) {
                errx(EXIT_FAILURE, "unknown filter: %s", filter_name);
            }
            result = filter_fn(result);
            break;
        }


        mpc_ast_t *op = expr->children[offset+2];
        mpc_ast_t *right_node = expr->children[offset+4];
        struct unja_object *right = eval_expression(right_node, ctx);
        result = eval_infix_expression(left, op->contents, right);

        left = result;
        offset += 4;
    }

    return result;
   
}

int eval(struct buffer *buf, mpc_ast_t* t, struct context *ctx) {
    static int trim_whitespace = 0;

    // maybe eat whitespace going backward
    if (t->children_num > 0 && strstr(t->children[0]->contents, "-")) {
        buf->string = trim_trailing_whitespace(buf->string);
    }

    if (strstr(t->tag, "content|text")) {
        char *str = t->contents;
        if (trim_whitespace) {
            str = trim_leading_whitespace(str);
            trim_whitespace = 0;
        }

        buffer_reserve(buf, strlen(str));
        strcat(buf->string, str);
        return 0;
    }

    if (strstr(t->tag, "content|statement|block")) {
        trim_whitespace = strstr(t->children[3]->contents, "-") ? 1 : 0;
        char *block_name = t->children[2]->contents;
        
        // find block in "lowest" template
        struct template *templ = ctx->current_template;
        mpc_ast_t *block = hashmap_get(templ->blocks, block_name);
        while (templ != NULL && block == NULL) {
            templ = hashmap_get(ctx->env->templates, templ->parent);
            block = hashmap_get(templ->blocks, block_name);
        }
        
        if (block) {
            eval(buf, block->children[4], ctx);
        } else {
            /* block not found in any lower template, so just render the one we got */
            eval(buf, t->children[4], ctx);
        }

        trim_whitespace = strstr(t->children[7]->contents, "-") ? 1 : 0;
        return 0;
    }

    // eval print statement
    if (strstr(t->tag, "content|print")) {
        trim_whitespace = strstr(t->children[2]->contents, "-") ? 1 : 0;
        mpc_ast_t *expr = t->children[1];      
        struct unja_object *obj = eval_expression(expr, ctx);  
        eval_object(buf, obj);
        object_free(obj);
        return 0;
    }

    if (strstr(t->tag, "content|statement|for")) {
        char *tmp_key = t->children[2]->contents;
        char *iterator_key = t->children[4]->contents;
        struct vector *list = hashmap_resolve(ctx->vars, iterator_key);

        /* add "loop" variable to context */
        struct hashmap *loop = hashmap_new();
        char index[8], first[2], last[2];
        hashmap_insert(loop, "index", index);
        hashmap_insert(loop, "first", first);
        hashmap_insert(loop, "last", last);
        hashmap_insert(ctx->vars, "loop", loop);

        /* loop over values in vector */
        for (int i=0; i < list->size; i++) {
            /* set loop variable values */
            sprintf(index, "%d", i);
            sprintf(first, "%d", i == 0);
            sprintf(last, "%d", i == (list->size - 1));
            hashmap_insert(ctx->vars, tmp_key, list->values[i]);
            trim_whitespace = strstr(t->children[5]->contents, "-") ? 1 : 0;

            /* evaluate body */
            eval(buf, t->children[6], ctx);
        }

        /* remove "loop" variable from context */
        hashmap_remove(ctx->vars, "loop");
        hashmap_free(loop);

        /* trim trailing whitespace if closing tag has minus sign */
        if (strstr(t->children[7]->contents, "-")) {
            buf->string = trim_trailing_whitespace(buf->string);
        }
        
        trim_whitespace = strstr(t->children[9]->contents, "-") ? 1 : 0;
        return 0;
    }

    if (strstr(t->tag, "content|statement|if")) {
        mpc_ast_t *expr = t->children[2];
        struct unja_object *result = eval_expression(expr, ctx);

        if (object_is_truthy(result)) {
            trim_whitespace = strstr(t->children[3]->contents, "-") ? 1 : 0;

            eval(buf, t->children[4], ctx);

            /* trim trailing whitespace if closing tag has minus sign */
            if (strstr(t->children[5]->contents, "-")) {
                buf->string = trim_trailing_whitespace(buf->string);
            }

            trim_whitespace = strstr(t->children[7]->contents, "-") ? 1 : 0;
        } else {
            if (t->children_num > 8) {
                trim_whitespace = strstr(t->children[7]->contents, "-") ? 1 : 0;
                eval(buf, t->children[8], ctx);

                 /* trim trailing whitespace if closing tag has minus sign */
                if (strstr(t->children[9]->contents, "-")) {
                    buf->string = trim_trailing_whitespace(buf->string);
                }

                trim_whitespace = strstr(t->children[11]->contents, "-") ? 1 : 0;
            }
        }

        object_free(result);
        return 0;
    }

    for (int i=0; i < t->children_num; i++) {
        eval(buf, t->children[i], ctx);
    }

    return 0;
}

char *render_ast(mpc_ast_t *ast, struct context *ctx) {
    #if DEBUG
    printf("AST: \n");
    mpc_ast_print(ast);
    printf("\n");
    #endif

    struct buffer buf;
    buf.size = 0;
    buf.cap = 256;
    buf.string = malloc(buf.cap);
    buf.string[0] = '\0';
    eval(&buf, ast, ctx);
    return buf.string;
}

struct unja_object *filter_trim(struct unja_object *obj) {
    assert(obj->type == OBJ_STRING);
    obj->string = trim_leading_whitespace(obj->string);
    trim_trailing_whitespace(obj->string);
    return obj;
}

struct unja_object *filter_lower(struct unja_object *obj) {
    assert(obj->type == OBJ_STRING);
    int len = strlen(obj->string);
    for (int i=0; i < len; i++) {
        obj->string[i] = tolower(obj->string[i]);
    }
    return obj;
}

struct unja_object *filter_wordcount(struct unja_object *obj) {
    assert(obj->type == OBJ_STRING);
    int len = strlen(obj->string);
    int word_count = 1;
    for (int i=0; i < len; i++) {
        if (isspace(obj->string[i])) {
            word_count++;
        }
    }

    object_free(obj);
    return make_int_object(word_count);
}

struct hashmap *default_filters() {
    struct hashmap *filters = hashmap_new();
    hashmap_insert(filters, "trim", filter_trim);
    hashmap_insert(filters, "lower", filter_lower);
    hashmap_insert(filters, "wordcount", filter_wordcount);
    return filters;
}

char *template_string(char *tmpl, struct hashmap *vars) {
    #if DEBUG
    printf("Template: %s\n", tmpl);
    #endif
    mpc_ast_t *ast = parse(tmpl);    
    struct context ctx;
    ctx.filters = default_filters();
    ctx.vars = vars;
    ctx.env = NULL;
    ctx.current_template = NULL;    
    char *output = render_ast(ast, &ctx);
    mpc_ast_delete(ast);
    return output;
}

char *template(struct env *env, char *template_name, struct hashmap *vars) {
    struct template *t = hashmap_get(env->templates, template_name);

    #if DEBUG
    printf("Template name: %s\n", t->name);
    printf("Parent: %s\n", t->parent ? t->parent : "None");
    #endif
    struct context ctx;
    ctx.vars = vars;
    ctx.env = env;
    ctx.current_template = t;    

    // find root template
    while (t->parent != NULL) {
        char *parent_name = t->parent;
        t = hashmap_get(env->templates, parent_name);

        if (t == NULL) {
            errx(EXIT_FAILURE, "template tried to extend unexisting parent \"%s\"", parent_name);
            break;
        }
    }

    return render_ast(t->ast, &ctx);
}