/**
 * @file node.h
 *
 * Functions related to nodes in the AST.
 */
#ifndef PRISM_NODE_H
#define PRISM_NODE_H

#include "prism/compiler/exported.h"
#include "prism/compiler/nonnull.h"

#include "prism/ast.h"

#ifdef __cplusplus
extern "C" {
#endif

/**
 * Loop through each node in the node list, writing each node to the given
 * pm_node_t pointer.
 */
#define PM_NODE_LIST_FOREACH(list, index, node) \
    for (size_t index = 0; index < (list)->size && ((node) = (list)->nodes[index]); index++)

/**
 * Append a node to the end of a node list. If the list is full, its storage is
 * grown by allocating from the given arena, so the arena must live as long as
 * the list does. For a list in a parsed tree, that is the arena that was passed
 * to pm_parser_new.
 *
 * @param arena The arena to allocate the list's storage from.
 * @param list The list to append to.
 * @param node The node to append.
 */
PRISM_EXPORTED_FUNCTION void pm_node_list_append(pm_arena_t *arena, pm_node_list_t *list, pm_node_t *node) PRISM_NONNULL(1, 2, 3);

/**
 * Returns a string representation of the given node type.
 *
 * @param node_type The node type to convert to a string.
 * @returns A string representation of the given node type.
 */
PRISM_EXPORTED_FUNCTION const char * pm_node_type(pm_node_type_t node_type);

/**
 * The value returned by a visitor callback, which determines where the walk
 * goes next.
 */
typedef enum {
    /** Continue the walk without visiting this node's children. */
    PM_VISIT_SKIP,

    /** Continue the walk by visiting this node's children. */
    PM_VISIT_DESCEND,

    /** End the walk without visiting any more nodes. */
    PM_VISIT_STOP
} pm_visit_result_t;

/**
 * A callback that is called for each node visited by pm_visit_node and
 * pm_visit_child_nodes. The data parameter is the opaque pointer that was
 * passed to the function that started the walk.
 */
typedef pm_visit_result_t (*pm_visit_callback_t)(const pm_node_t *node, void *data);

/**
 * Visit each of the nodes in this subtree using the given visitor callback. The
 * callback function will be called for each node in the subtree, and its
 * return value determines whether the walk visits that node's children, skips
 * them, or stops entirely. The data parameter is treated as an opaque pointer
 * and is passed to the visitor callback for consumers to use as they see fit.
 *
 * As an example:
 *
 * ```c
 * #include "prism.h"
 *
 * pm_visit_result_t visit(const pm_node_t *node, void *data) {
 *     size_t *indent = (size_t *) data;
 *     for (size_t i = 0; i < *indent * 2; i++) putc(' ', stdout);
 *     printf("%s\n", pm_node_type(node->type));
 *
 *     size_t next_indent = *indent + 1;
 *     size_t *next_data = &next_indent;
 *     pm_visit_child_nodes(node, visit, next_data);
 *
 *     return PM_VISIT_SKIP;
 * }
 *
 * int main(void) {
 *     const char *source = "1 + 2; 3 + 4";
 *     size_t size = strlen(source);
 *
 *     pm_arena_t *arena = pm_arena_new();
 *     pm_options_t *options = pm_options_new();
 *
 *     pm_parser_t *parser = pm_parser_new(arena, (const uint8_t *) source, size, options);
 *
 *     size_t indent = 0;
 *     pm_node_t *node = pm_parse(parser);
 *
 *     size_t *data = &indent;
 *     pm_visit_node(node, visit, data);
 *
 *     pm_parser_free(parser);
 *     pm_options_free(options);
 *     pm_arena_free(arena);
 *
 *     return EXIT_SUCCESS;
 * }
 * ```
 *
 * @param node The root node to start visiting from.
 * @param visitor The callback to call for each node in the subtree.
 * @param data An opaque pointer that is passed to the visitor callback.
 * @returns false if the visitor stopped the walk by returning PM_VISIT_STOP,
 *     true otherwise.
 */
PRISM_EXPORTED_FUNCTION bool pm_visit_node(const pm_node_t *node, pm_visit_callback_t visitor, void *data) PRISM_NONNULL(1);

/**
 * Visit the children of the given node with the given callback. This is the
 * default behavior for walking the tree that is called from pm_visit_node if
 * the callback returns PM_VISIT_DESCEND.
 *
 * @param node The node to visit the children of.
 * @param visitor The callback to call for each child node.
 * @param data An opaque pointer that is passed to the visitor callback.
 * @returns false if the visitor stopped the walk by returning PM_VISIT_STOP,
 *     true otherwise.
 */
PRISM_EXPORTED_FUNCTION bool pm_visit_child_nodes(const pm_node_t *node, pm_visit_callback_t visitor, void *data) PRISM_NONNULL(1);

#ifdef __cplusplus
}
#endif

#endif