uci: add module documentation

Add complete JSDoc documentation coverage for the uci module.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

1 files changed, 842 insertions, 0 deletions

diff --git a/lib/uci.c b/lib/uci.c
index b7319bf..96cce6a 100644
--- a/lib/uci.c
+++ b/lib/uci.c
@@ -14,6 +14,40 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
+/**
+ * # OpenWrt UCI configuration
+ *
+ * The `uci` module provides access to the native OpenWrt
+ * {@link https://github.com/openwrt/uci libuci} API for reading and
+ * manipulating UCI configuration files.
+ *
+ * Functions can be individually imported and directly accessed using the
+ * {@link https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/import#named_import named import}
+ * syntax:
+ *
+ *   ```
+ *   import { cursor } from 'uci';
+ *
+ *   let ctx = cursor();
+ *   let hostname = ctx.get_first('system', 'system', 'hostname');
+ *   ```
+ *
+ * Alternatively, the module namespace can be imported
+ * using a wildcard import statement:
+ *
+ *   ```
+ *   import * as uci from 'uci';
+ *
+ *   let ctx = uci.cursor();
+ *   let hostname = ctx.get_first('system', 'system', 'hostname');
+ *   ```
+ *
+ * Additionally, the uci module namespace may also be imported by invoking
+ * the `ucode` interpreter with the `-luci` switch.
+ *
+ * @module uci
+ */
+
 #include <string.h>
 #include <uci.h>
 
@@ -30,6 +64,24 @@ enum pkg_cmd {
 	CMD_REVERT
 };
 
+/**
+ * Query error information.
+ *
+ * Returns a string containing a description of the last occurred error or
+ * `null` if there is no error information.
+ *
+ * @function module:uci#error
+ *
+ * @returns {?string}
+ *
+ * @example
+ * // Trigger error
+ * const ctx = cursor();
+ * ctx.set("not_existing_config", "test", "1");
+ *
+ * // Print error (should yield "Entry not found")
+ * print(ctx.error(), "\n");
+ */
 static uc_value_t *
 uc_uci_error(uc_vm_t *vm, size_t nargs)
 {
@@ -63,6 +115,38 @@ uc_uci_error(uc_vm_t *vm, size_t nargs)
 }
 
 
+/**
+ * Instantiate uci cursor.
+ *
+ * A uci cursor is a context for interacting with uci configuration files. It's
+ * purpose is to cache and hold changes made to loaded configuration states
+ * until those changes are written out to disk or discared.
+ *
+ * Unsaved and uncommitted changes in a cursor instance are private and not
+ * visible to other cursor instances instantiated by the same program or other
+ * processes on the system.
+ *
+ * Returns the instantiated cursor on success.
+ *
+ * Returns `null` on error, e.g. if an invalid path argument was provided.
+ *
+ * @function module:uci#cursor
+ *
+ * @param {string} [config_dir=/etc/config]
+ * The directory to search for configuration files. It defaults to the well
+ * known uci configuration directory `/etc/config` but may be set to a different
+ * path for special purpose applications.
+ *
+ * @param {string} [delta_dir=/tmp/.uci]
+ * The directory to save delta records in. It defaults to the well known
+ * `/tmp/.uci` path which is used as default by the uci command line tool.
+ *
+ * By changing this path to a different location, it is possible to isolate
+ * uncommitted application changes from the uci cli or other processes on the
+ * system.
+ *
+ * @returns {?module:uci.cursor}
+ */
 static uc_value_t *
 uc_uci_cursor(uc_vm_t *vm, size_t nargs)
 {
@@ -98,6 +182,164 @@ uc_uci_cursor(uc_vm_t *vm, size_t nargs)
 }
 
 
+/**
+ * Represents a context for interacting with uci configuration files.
+ *
+ * Operations on uci configurations are performed through a uci cursor object
+ * which operates on in-memory representations of loaded configuration files.
+ *
+ * Any changes made to configuration values are local to the cursor object and
+ * held in memory only until they're written out to the filesystem using the
+ * `save()` and `commit()` methods.
+ *
+ * Changes performed in one cursor instance are not reflected in another, unless
+ * the first instance writes those changes to the filesystem and the other
+ * instance explicitly (re)loads the affected configuration files.
+ *
+ * @class module:uci.cursor
+ * @hideconstructor
+ *
+ * @borrows module:uci#error as module.uci.cursor#error
+ *
+ * @see {@link module:uci#cursor|cursor()}
+ *
+ * @example
+ *
+ * const ctx = cursor(…);
+ *
+ * // Enumerate configuration files
+ * ctx.configs();
+ *
+ * // Load configuration files
+ * ctx.load(…);
+ * ctx.unload(…);
+ *
+ * // Query values
+ * ctx.get(…);
+ * ctx.get_all(…);
+ * ctx.get_first(…);
+ * ctx.foreach(…);
+ *
+ * // Modify values
+ * ctx.add(…);
+ * ctx.set(…);
+ * ctx.rename(…);
+ * ctx.reorder(…);
+ * ctx.delete(…);
+ *
+ * // Stage, revert, save changes
+ * ctx.changes(…);
+ * ctx.save(…);
+ * ctx.revert(…);
+ * ctx.commit(…);
+ */
+
+/**
+ * A uci change record is a plain array containing the change operation name as
+ * first element, the affected section ID as second argument and an optional
+ * third and fourth argument whose meanings depend on the operation.
+ *
+ * @typedef {string[]} ChangeRecord
+ * @memberof module:uci.cursor
+ *
+ * @property {string} 0
+ * The operation name - may be one of `add`, `set`, `remove`, `order`,
+ * `list-add`, `list-del` or `rename`.
+ *
+ * @property {string} 1
+ * The section ID targeted by the operation.
+ *
+ * @property {string} 2
+ * The meaning of the third element depends on the operation.
+ * - For `add` it is type of the section that has been added
+ * - For `set` it either is the option name if a fourth element exists, or the
+ *   type of a named section which has been added when the change entry only
+ *   contains three elements.
+ * - For `remove` it contains the name of the option that has been removed.
+ * - For `order` it specifies the new sort index of the section.
+ * - For `list-add` it contains the name of the list option a new value has been
+ *   added to.
+ * - For `list-del` it contains the name of the list option a value has been
+ *   removed from.
+ * - For `rename` it contains the name of the option that has been renamed if a
+ *   fourth element exists, else it contains the new name a section has been
+ *   renamed to if the change entry only contains three elements.
+ *
+ * @property {string} 4
+ * The meaning of the fourth element depends on the operation.
+ * - For `set` it is the value an option has been set to.
+ * - For `list-add` it is the new value that has been added to a list option.
+ * - For `rename` it is the new name of an option that has been renamed.
+ */
+
+/**
+ * A section object represents the options and their corresponding values
+ * enclosed within a configuration section, as well as some additional meta data
+ * such as sort indexes and internal ID.
+ *
+ * Any internal metadata fields are prefixed with a dot which isn't an allowed
+ * character for normal option names.
+ *
+ * @typedef {Object<string, boolean|number|string|string[]>} SectionObject
+ * @memberof module:uci.cursor
+ *
+ * @property {boolean} .anonymous
+ * The `.anonymous` property specifies whether the configuration is
+ * anonymous (`true`) or named (`false`).
+ *
+ * @property {number} .index
+ * The `.index` property specifies the sort order of the section.
+ *
+ * @property {string} .name
+ * The `.name` property holds the name of the section object. It may be either
+ * an anonymous ID in the form `cfgXXXXXX` with `X` being a hexadecimal digit or
+ * a string holding the name of the section.
+ *
+ * @property {string} .type
+ * The `.type` property contains the type of the corresponding uci
+ * section.
+ *
+ * @property {string|string[]} *
+ * A section object may contain an arbitrary number of further properties
+ * representing the uci option enclosed in the section.
+ *
+ * All option property names will be in the form `[A-Za-z0-9_]+` and either
+ * contain a string value or an array of strings, in case the underlying option
+ * is an UCI list.
+ */
+
+/**
+ * The sections callback is invoked for each section found within the given
+ * configuration and receives the section object and its associated name as
+ * arguments.
+ *
+ * @callback module:uci.cursor.SectionCallback
+ *
+ * @param {module:uci.cursor.SectionObject} section
+ * The section object.
+ */
+
+/**
+ * Explicitly reload configuration file.
+ *
+ * Usually, any attempt to query or modify a value within a given configuration
+ * will implicitly load the underlying file into memory. By invoking `load()`
+ * explicitly, a potentially loaded stale configuration is discarded and
+ * reloaded from the file system, ensuring that the latest state is reflected in
+ * the cursor.
+ *
+ * Returns `true` if the configuration was successfully loaded.
+ *
+ * Returns `null` on error, e.g. if the requested configuration does not exist.
+ *
+ * @function module:uci.cursor#load
+ *
+ * @param {string} config
+ * The name of the configuration file to load, e.g. `"system"` to load
+ * `/etc/config/system` into the cursor.
+ *
+ * @returns {?boolean}
+ */
 static uc_value_t *
 uc_uci_load(uc_vm_t *vm, size_t nargs)
 {
@@ -127,6 +369,26 @@ uc_uci_load(uc_vm_t *vm, size_t nargs)
 	return ucv_boolean_new(true);
 }
 
+/**
+ * Explicitly unload configuration file.
+ *
+ * The `unload()` function forcibly discards a loaded configuration state from
+ * the cursor so that the next attempt to read or modify that configuration
+ * will load it anew from the file system.
+ *
+ * Returns `true` if the configuration was successfully unloaded.
+ *
+ * Returns `false` if the configuration was not loaded to begin with.
+ *
+ * Returns `null` on error, e.g. if the requested configuration does not exist.
+ *
+ * @function module:uci.cursor#unload
+ *
+ * @param {string} config
+ * The name of the configuration file to unload.
+ *
+ * @returns {?boolean}
+ */
 static uc_value_t *
 uc_uci_unload(uc_vm_t *vm, size_t nargs)
 {
@@ -308,18 +570,139 @@ uc_uci_get_any(uc_vm_t *vm, size_t nargs, bool all)
 	return ucv_string_new(ptr.s->type);
 }
 
+/**
+ * Query a single option value or section type.
+ *
+ * When invoked with three arguments, the function returns the value of the
+ * given option, within the specified section of the given configuration.
+ *
+ * When invoked with just a config and section argument, the function returns
+ * the type of the specified section.
+ *
+ * In either case, the given configuration is implicitly loaded into the cursor
+ * if not already present.
+ *
+ * Returns the configuration value or section type on success.
+ *
+ * Returns `null` on error, e.g. if the requested configuration does not exist
+ * or if an invalid argument was passed.
+ *
+ * @function module:uci.cursor#get
+ *
+ * @param {string} config
+ * The name of the configuration file to query, e.g. `"system"` to query values
+ * in `/etc/config/system`.
+ *
+ * @param {string} section
+ * The name of the section to query within the configuration.
+ *
+ * @param {string} [option]
+ * The name of the option to query within the section. If omitted, the type of
+ * the section is returned instead.
+ *
+ * @returns {?(string|string[])}
+ *
+ * @example
+ * const ctx = cursor(…);
+ *
+ * // Query an option, extended section notation is supported
+ * ctx.get('system', '@system[0]', 'hostname');
+ *
+ * // Query a section type (should yield 'interface')
+ * ctx.get('network', 'lan');
+ */
 static uc_value_t *
 uc_uci_get(uc_vm_t *vm, size_t nargs)
 {
 	return uc_uci_get_any(vm, nargs, false);
 }
 
+/**
+ * Query a complete section or configuration.
+ *
+ * When invoked with two arguments, the function returns all values of the
+ * specified section within the given configuration as dictionary.
+ *
+ * When invoked with just a config argument, the function returns a nested
+ * dictionary of all sections present within the given configuration.
+ *
+ * In either case, the given configuration is implicitly loaded into the cursor
+ * if not already present.
+ *
+ * Returns the section or configuration dictionary on success.
+ *
+ * Returns `null` on error, e.g. if the requested configuration does not exist
+ * or if an invalid argument was passed.
+ *
+ * @function module:uci.cursor#get_all
+ *
+ * @param {string} config
+ * The name of the configuration file to query, e.g. `"system"` to query values
+ * in `/etc/config/system`.
+ *
+ * @param {string} [section]
+ * The name of the section to query within the configuration. If omitted a
+ * nested dictionary containing all section values is returned.
+ *
+ * @returns {?(Object<string, module:uci.cursor.SectionObject>|module:uci.cursor.SectionObject)}
+ *
+ * @example
+ * const ctx = cursor(…);
+ *
+ * // Query all lan interface details
+ * ctx.get_all('network', 'lan');
+ *
+ * // Dump the entire dhcp configuration
+ * ctx.get_all('dhcp');
+ */
 static uc_value_t *
 uc_uci_get_all(uc_vm_t *vm, size_t nargs)
 {
 	return uc_uci_get_any(vm, nargs, true);
 }
 
+/**
+ * Query option value or name of first section of given type.
+ *
+ * When invoked with three arguments, the function returns the value of the
+ * given option within the first found section of the specified type in the
+ * given configuration.
+ *
+ * When invoked with just a config and section type argument, the function
+ * returns the name of the first found section of the given type.
+ *
+ * In either case, the given configuration is implicitly loaded into the cursor
+ * if not already present.
+ *
+ * Returns the configuration value or section name on success.
+ *
+ * Returns `null` on error, e.g. if the requested configuration does not exist
+ * or if an invalid argument was passed.
+ *
+ * @function module:uci.cursor#get_first
+ *
+ * @param {string} config
+ * The name of the configuration file to query, e.g. `"system"` to query values
+ * in `/etc/config/system`.
+ *
+ * @param {string} type
+ * The section type to find the first section for within the configuration.
+ *
+ * @param {string} [option]
+ * The name of the option to query within the section. If omitted, the name of
+ * the section is returned instead.
+ *
+ * @returns {?(string|string[])}
+ *
+ * @example
+ * const ctx = cursor(…);
+ *
+ * // Query hostname in first anonymous "system" section of /etc/config/system
+ * ctx.get_first('system', 'system', 'hostname');
+ *
+ * // Figure out name of first network interface section (usually "loopback")
+ * ctx.get_first('network', 'interface');
+ */
 static uc_value_t *
 uc_uci_get_first(uc_vm_t *vm, size_t nargs)
 {
@@ -378,6 +761,49 @@ uc_uci_get_first(uc_vm_t *vm, size_t nargs)
 	err_return(UCI_ERR_NOTFOUND);
 }
 
+/**
+ * Add anonymous section to given configuration.
+ *
+ * Adds a new anonymous (unnamed) section of the specified type to the given
+ * configuration. In order to add a named section, the three argument form of
+ * `set()` should be used instead.
+ *
+ * In contrast to other query functions, `add()` will not implicitly load the
+ * configuration into the cursor. The configuration either needs to be loaded
+ * explicitly through `load()` beforehand, or implicitly by querying it through
+ * one of the `get()`, `get_all()`, `get_first()` or `foreach()` functions.
+ *
+ * Returns the autogenerated, ephemeral name of the added unnamed section
+ * on success.
+ *
+ * Returns `null` on error, e.g. if the targeted configuration was not loaded or
+ * if an invalid section type value was passed.
+ *
+ * @function module:uci.cursor#add
+ *
+ * @param {string} config
+ * The name of the configuration file to add the section to, e.g. `"system"` to
+ * modify `/etc/config/system`.
+ *
+ * @param {string} type
+ * The type value to use for the added section.
+ *
+ * @returns {?string}
+ *
+ * @example
+ * const ctx = cursor(…);
+ *
+ * // Load firewall configuration
+ * ctx.load('firewall');
+ *
+ * // Add unnamed `config rule` section
+ * const sid = ctx.add('firewall', 'rule');
+ *
+ * // Set values on the newly added section
+ * ctx.set('firewall', sid, 'name', 'A test');
+ * ctx.set('firewall', sid, 'target', 'ACCEPT');
+ * …
+ */
 static uc_value_t *
 uc_uci_add(uc_vm_t *vm, size_t nargs)
 {
@@ -458,6 +884,60 @@ uval_to_uci(uc_vm_t *vm, uc_value_t *val, const char **p, bool *is_list)
 	}
 }
 
+/**
+ * Set option value or add named section in given configuration.
+ *
+ * When invoked with four arguments, the function sets the value of the given
+ * option within the specified section of the given configuration to the
+ * provided value. A value of `""` (empty string) can be used to delete an
+ * existing option.
+ *
+ * When invoked with three arguments, the function adds a new named section to
+ * the given configuration, using the specified type.
+ *
+ * In either case, the given configuration is implicitly loaded into the cursor
+ * if not already present.
+ *
+ * Returns the `true` if the named section was added or the specified option was
+ * set.
+ *
+ * Returns `null` on error, e.g. if the targeted configuration was not found or
+ * if an invalid value was passed.
+ *
+ * @function module:uci.cursor#set
+ *
+ * @param {string} config
+ * The name of the configuration file to set values in, e.g. `"system"` to
+ * modify `/etc/config/system`.
+ *
+ * @param {string} section
+ * The section name to create or set a value in.
+ *
+ * @param {string} option_or_type
+ * The option name to set within the section or, when the subsequent value
+ * argument is omitted, the type of the section to create within the
+ * configuration.
+ *
+ * @param {(Array<string|boolean|number>|string|boolean|number)} [value]
+ * The option value to set.
+ *
+ * @returns {?boolean}
+ *
+ * @example
+ * const ctx = cursor(…);
+ *
+ * // Add named `config interface guest` section
+ * ctx.set('network', 'guest', 'interface');
+ *
+ * // Set values on the newly added section
+ * ctx.set('network', 'guest', 'proto', 'static');
+ * ctx.set('network', 'guest', 'ipaddr', '10.0.0.1/24');
+ * ctx.set('network', 'guest', 'dns', ['8.8.4.4', '8.8.8.8']);
+ * …
+ *
+ * // Delete 'disabled' option in first wifi-iface section
+ * ctx.set('wireless', '@wifi-iface[0]', 'disabled', '');
+ */
 static uc_value_t *
 uc_uci_set(uc_vm_t *vm, size_t nargs)
 {
@@ -563,6 +1043,50 @@ uc_uci_set(uc_vm_t *vm, size_t nargs)
 	return ucv_boolean_new(true);
 }
 
+/**
+ * Delete an option or section from given configuration.
+ *
+ * When invoked with three arguments, the function deletes the given option
+ * within the specified section of the given configuration.
+ *
+ * When invoked with two arguments, the function deletes the entire specified
+ * section within the given configuration.
+ *
+ * In either case, the given configuration is implicitly loaded into the cursor
+ * if not already present.
+ *
+ * Returns the `true` if specified option or section has been deleted.
+ *
+ * Returns `null` on error, e.g. if the targeted configuration was not found or
+ * if an invalid value was passed.
+ *
+ * @function module:uci.cursor#delete
+ *
+ * @param {string} config
+ * The name of the configuration file to delete values in, e.g. `"system"` to
+ * modify `/etc/config/system`.
+ *
+ * @param {string} section
+ * The section name to remove the specified option in or, when the subsequent
+ * argument is omitted, the section to remove entirely.
+ *
+ * @param {string} [option]
+ * The option name to remove within the section.
+ *
+ * @returns {?boolean}
+ *
+ * @example
+ * const ctx = cursor(…);
+ *
+ * // Delete 'disabled' option in first wifi-iface section
+ * ctx.delete('wireless', '@wifi-iface[0]', 'disabled');
+ *
+ * // Delete 'wan' interface
+ * ctx.delete('network', 'lan');
+ *
+ * // Delete last firewall rule
+ * ctx.delete('firewall', '@rule[-1]');
+ */
 static uc_value_t *
 uc_uci_delete(uc_vm_t *vm, size_t nargs)
 {
@@ -598,6 +1122,55 @@ uc_uci_delete(uc_vm_t *vm, size_t nargs)
 	return ucv_boolean_new(true);
 }
 
+/**
+ * Rename an option or section in given configuration.
+ *
+ * When invoked with four arguments, the function renames the given option
+ * within the specified section of the given configuration to the provided
+ * value.
+ *
+ * When invoked with three arguments, the function renames the entire specified
+ * section to the provided value.
+ *
+ * In either case, the given configuration is implicitly loaded into the cursor
+ * if not already present.
+ *
+ * Returns the `true` if specified option or section has been renamed.
+ *
+ * Returns `null` on error, e.g. if the targeted configuration was not found or
+ * if an invalid value was passed.
+ *
+ * @function module:uci.cursor#rename
+ *
+ * @param {string} config
+ * The name of the configuration file to rename values in, e.g. `"system"` to
+ * modify `/etc/config/system`.
+ *
+ * @param {string} section
+ * The section name to rename or to rename an option in.
+ *
+ * @param {string} option_or_name
+ * The option name to rename within the section or, when the subsequent name
+ * argument is omitted, the new name of the renamed section within the
+ * configuration.
+ *
+ * @param {string} [name]
+ * The new name of the option to rename.
+ *
+ * @returns {?boolean}
+ *
+ * @example
+ * const ctx = cursor(…);
+ *
+ * // Assign explicit name to last anonymous firewall rule section
+ * ctx.rename('firewall', '@rule[-1]', 'my_block_rule');
+ *
+ * // Rename 'server' to 'orig_server_list' in ntp section of system config
+ * ctx.rename('system', 'ntp', 'server', 'orig_server_list');
+ *
+ * // Rename 'wan' interface to 'external'
+ * ctx.rename('network', 'wan', 'external');
+ */
 static uc_value_t *
 uc_uci_rename(uc_vm_t *vm, size_t nargs)
 {
@@ -658,6 +1231,74 @@ uc_uci_rename(uc_vm_t *vm, size_t nargs)
 	return ucv_boolean_new(true);
 }
 
+/**
+ * Reorder sections in given configuration.
+ *
+ * The `reorder()` function moves a single section by repositioning it to the
+ * given index within the configurations section list.
+ *
+ * The given configuration is implicitly loaded into the cursor if not already
+ * present.
+ *
+ * Returns the `true` if specified section has been moved.
+ *
+ * Returns `null` on error, e.g. if the targeted configuration was not found or
+ * if an invalid value was passed.
+ *
+ * @function module:uci.cursor#reorder
+ *
+ * @param {string} config
+ * The name of the configuration file to move the section in, e.g. `"system"` to
+ * modify `/etc/config/system`.
+ *
+ * @param {string} section
+ * The section name to move.
+ *
+ * @param {number} index
+ * The target index to move the section to, starting from `0`.
+ *
+ * @param {string} [name]
+ * The new name of the option to rename.
+ *
+ * @returns {?boolean}
+ *
+ * @example
+ * const ctx = cursor(…);
+ *
+ * // Query whole firewall config and reorder resulting dict by type and name
+ * const type_order = ['defaults', 'zone', 'forwarding', 'redirect', 'rule'];
+ * const values = ctx.get_all('firewall');
+ *
+ * sort(values, (k1, k2, s1, s2) => {
+ *     // Get weight from type_order array
+ *     let w1 = index(type_order, s1['.type']);
+ *     let w2 = index(type_order, s2['.type']);
+ *
+ *     // For unknown type orders, use type value itself as weight
+ *     if (w1 == -1) w1 = s1['.type'];
+ *     if (w2 == -1) w2 = s2['.type'];
+ *
+ *     // Get name from name option, fallback to section name
+ *     let n1 = s1.name ?? k1;
+ *     let n2 = s2.name ?? k2;
+ *
+ *     // Order by weight
+ *     if (w1 < w2) return -1;
+ *     if (w1 > w2) return 1;
+ *
+ *     // For same weight order by name
+ *     if (n1 < n2) return -1;
+ *     if (n1 > n2) return 1;
+ *
+ *     return 0;
+ * });
+ *
+ * // Sequentially reorder sorted sections in firewall configuration
+ * let position = 0;
+ *
+ * for (let sid in values)
+ *   ctx.reorder('firewall', sid, position++);
+ */
 static uc_value_t *
 uc_uci_reorder(uc_vm_t *vm, size_t nargs)
 {
@@ -766,18 +1407,125 @@ uc_uci_pkg_command(uc_vm_t *vm, size_t nargs, enum pkg_cmd cmd)
 	return ucv_boolean_new(true);
 }
 
+/**
+ * Save accumulated cursor changes to delta directory.
+ *
+ * The `save()` function writes consolidated changes made to in-memory copies of
+ * loaded configuration files to the uci delta directory which effectively makes
+ * them available to other processes using the same delta directory path as well
+ * as the `uci changes` cli command when using the default delta directory.
+ *
+ * Note that uci deltas are overlayed over the actual configuration file values
+ * so they're reflected by `get()`, `foreach()` etc. even if the underlying
+ * configuration files are not actually changed (yet). The delta records may be
+ * either permanently merged into the configuration by invoking `commit()` or
+ * reverted through `revert()` in order to restore the current state of the
+ * underlying configuration file.
+ *
+ * When the optional "config" parameter is omitted, delta records for all
+ * currently loaded configuration files are written.
+ *
+ * In case that neither sharing changes with other processes nor any revert
+ * functionality is required, changes may be committed directly using `commit()`
+ * instead, bypassing any delta record creation.
+ *
+ * Returns the `true` if operation completed successfully.
+ *
+ * Returns `null` on error, e.g. if the requested configuration was not loaded
+ * or when a file system error occurred.
+ *
+ * @function module:uci.cursor#save
+ *
+ * @param {string} [config]
+ * The name of the configuration file to save delta records for, e.g. `"system"`
+ * to store changes for `/etc/config/system`.
+ *
+ * @returns {?boolean}
+ *
+ * @example
+ * const ctx = cursor(…);
+ *
+ * ctx.set('wireless', '@wifi-iface[0]', 'disabled', '1');
+ * ctx.save('wireless');
+ *
+ * @see {@link module:uci.cursor#commit|commit()}
+ * @see {@link module:uci.cursor#revert|revert()}
+ */
 static uc_value_t *
 uc_uci_save(uc_vm_t *vm, size_t nargs)
 {
 	return uc_uci_pkg_command(vm, nargs, CMD_SAVE);
 }
 
+/**
+ * Update configuration files with accumulated cursor changes.
+ *
+ * The `commit()` function merges changes made to in-memory copies of loaded
+ * configuration files as well as existing delta records in the cursors
+ * configured delta directory and writes them back into the underlying
+ * configuration files, persistently committing changes to the file system.
+ *
+ * When the optional "config" parameter is omitted, all currently loaded
+ * configuration files with either present delta records or yet unsaved
+ * cursor changes are updated.
+ *
+ * Returns the `true` if operation completed successfully.
+ *
+ * Returns `null` on error, e.g. if the requested configuration was not loaded
+ * or when a file system error occurred.
+ *
+ * @function module:uci.cursor#commit
+ *
+ * @param {string} [config]
+ * The name of the configuration file to commit, e.g. `"system"` to update the
+ * `/etc/config/system` file.
+ *
+ * @returns {?boolean}
+ *
+ * @example
+ * const ctx = cursor(…);
+ *
+ * ctx.set('system', '@system[0]', 'hostname', 'example.org');
+ * ctx.commit('system');
+ */
 static uc_value_t *
 uc_uci_commit(uc_vm_t *vm, size_t nargs)
 {
 	return uc_uci_pkg_command(vm, nargs, CMD_COMMIT);
 }
 
+/**
+ * Revert accumulated cursor changes and associated delta records.
+ *
+ * The `revert()` function discards any changes made to in-memory copies of
+ * loaded configuration files and discards any related existing delta records in
+ * the  cursors configured delta directory.
+ *
+ * When the optional "config" parameter is omitted, all currently loaded
+ * configuration files with either present delta records or yet unsaved
+ * cursor changes are reverted.
+ *
+ * Returns the `true` if operation completed successfully.
+ *
+ * Returns `null` on error, e.g. if the requested configuration was not loaded
+ * or when a file system error occurred.
+ *
+ * @function module:uci.cursor#revert
+ *
+ * @param {string} [config]
+ * The name of the configuration file to revert, e.g. `"system"` to discard any
+ * changes for the `/etc/config/system` file.
+ *
+ * @returns {?boolean}
+ *
+ * @example
+ * const ctx = cursor(…);
+ *
+ * ctx.set('system', '@system[0]', 'hostname', 'example.org');
+ * ctx.revert('system');
+ *
+ * @see {@link module:uci.cursor#save|save()}
+ */
 static uc_value_t *
 uc_uci_revert(uc_vm_t *vm, size_t nargs)
 {
@@ -873,6 +1621,38 @@ changes_to_uval(uc_vm_t *vm, struct uci_context *ctx, const char *package)
 	return a;
 }
 
+/**
+ * Enumerate pending changes.
+ *
+ * The `changes()` function returns a list of change records for currently
+ * loaded configuration files, originating both from the cursors associated
+ * delta directory and yet unsaved cursor changes.
+ *
+ * When the optional "config" parameter is specified, the requested
+ * configuration is implicitly loaded if it not already loaded into the cursor.
+ *
+ * Returns a dictionary of change record arrays, keyed by configuration name.
+ *
+ * Returns `null` on error, e.g. if the requested configuration could not be
+ * loaded.
+ *
+ * @function module:uci.cursor#changes
+ *
+ * @param {string} [config]
+ * The name of the configuration file to enumerate changes for, e.g. `"system"`
+ * to query pending changes for the `/etc/config/system` file.
+ *
+ * @returns {?Object<string, module:uci.cursor.ChangeRecord[]>}
+ *
+ * @example
+ * const ctx = cursor(…);
+ *
+ * // Enumerate changes for all currently loaded configurations
+ * const deltas = ctx.changes();
+ *
+ * // Explicitly load and enumerate changes for the "system" configuration
+ * const deltas = ctx.changes('system');
+ */
 static uc_value_t *
 uc_uci_changes(uc_vm_t *vm, size_t nargs)
 {
@@ -907,6 +1687,48 @@ uc_uci_changes(uc_vm_t *vm, size_t nargs)
 	return res;
 }
 
+/**
+ * Iterate configuration sections.
+ *
+ * The `foreach()` function iterates all sections of the given configuration,
+ * optionally filtered by type, and invokes the given callback function for
+ * each encountered section.
+ *
+ * When the optional "type" parameter is specified, the callback is only invoked
+ * for sections of the given type, otherwise it is invoked for all sections.
+ *
+ * The requested configuration is implicitly loaded into the cursor.
+ *
+ * Returns `true` if the callback was executed successfully at least once.
+ *
+ * Returns `false` if the callback was never invoked, e.g. when the
+ * configuration is empty or contains no sections of the given type.
+ *
+ * Returns `null` on error, e.g. when an invalid callback was passed or the
+ * requested configuration not found.
+ *
+ * @function module:uci.cursor#foreach
+ *
+ * @param {string} config
+ * The configuration to iterate sections for, e.g. `"system"` to read the
+ * `/etc/config/system` file.
+ *
+ * @param {?string} type
+ * Invoke the callback only for sections of the specified type.
+ *
+ * @param {module:uci.cursor.SectionCallback} callback
+ * The callback to invoke for each section, will receive a section dictionary
+ * as sole argument.
+ *
+ * @returns {?boolean}
+ *
+ * @example
+ * const ctx = cursor(…);
+ *
+ * // Iterate all network interfaces
+ * ctx.foreach('network', 'interface',
+ * 	   section => print(`Have interface ${section[".name"]}\n`));
+ */
 static uc_value_t *
 uc_uci_foreach(uc_vm_t *vm, size_t nargs)
 {
@@ -967,6 +1789,26 @@ uc_uci_foreach(uc_vm_t *vm, size_t nargs)
 	return ucv_boolean_new(ret);
 }
 
+/**
+ * Enumerate existing configurations.
+ *
+ * The `configs()` function yields an array of configuration files present in
+ * the cursors associated configuration directory, `/etc/config/` by default.
+ *
+ * Returns an array of configuration names on success.
+ *
+ * Returns `null` on error, e.g. due to filesystem errors.
+ *
+ * @function module:uci.cursor#configs
+ *
+ * @returns {?string[]}
+ *
+ * @example
+ * const ctx = cursor(…);
+ *
+ * // Enumerate all present configuration file names
+ * const configurations = ctx.configs();
+ */
 static uc_value_t *
 uc_uci_configs(uc_vm_t *vm, size_t nargs)
 {