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fswalk.gleam
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fswalk.gleam
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import gleam/iterator.{type Iterator}
import gleam/list
import gleam/option.{type Option, None, Some}
import gleam/result
import gleam_community/path
import simplifile.{type FileError, read_directory, verify_is_directory}
@internal
pub type Non
@internal
pub type Som
/// See [builder](#builder).
///
pub opaque type WalkBuilder(traversal_filter, path) {
WalkBuilder(traversal_filter: Option(List(EntryFilter)), path: Option(String))
}
/// Create a new WalkBuilder
///
pub fn builder() -> WalkBuilder(Non, Non) {
WalkBuilder(traversal_filter: None, path: None)
}
/// Create a new WalkBuilder bound to a directory path to walk
///
pub fn with_path(
builder: WalkBuilder(t, p),
path: String,
) -> WalkBuilder(t, Som) {
WalkBuilder(traversal_filter: builder.traversal_filter, path: Some(path))
}
/// Create a new WalkBuilder adding an additional entry filter function.
///
pub fn with_traversal_filter(
builder: WalkBuilder(t, p),
traversal_filter: EntryFilter,
) -> WalkBuilder(Som, p) {
WalkBuilder(
traversal_filter: Some(
list.append(option.unwrap(builder.traversal_filter, []), [
traversal_filter,
]),
),
path: builder.path,
)
}
/// Walks the filesystem lazily.
///
pub fn walk(builder: WalkBuilder(t, Som)) {
let WalkBuilder(traversal_filter: traversal_filter_opt, path: path_opt) =
builder
let assert Some(root_path) = path_opt
let traversal_filters = case traversal_filter_opt {
Some(xs) -> xs
_ -> []
}
walk_path(path.from_string(root_path), traversal_filters)
}
/// Incomplete [stat](https://www.man7.org/linux/man-pages/man2/stat.2.html) data.
///
pub type Stat {
Stat(is_directory: Bool)
}
//
/// Data about the file/folder walked.
pub type Entry {
Entry(filename: String, stat: Stat)
}
//
/// A function that filters entries in the walk iterator.
pub type EntryFilter =
fn(Entry) -> Bool
fn to_entry(path: path.Path) -> Entry {
let filename = path.to_string(path)
Entry(
filename,
stat: Stat(
is_directory: verify_is_directory(filename)
|> result.unwrap(or: False),
),
)
}
fn filter_many(xs, filters) {
xs
|> list.filter(fn(entry) { list.all(filters, fn(f) { f(entry) }) })
}
/// Walk the filesystem, starting at the provided path.
///
fn walk_path(
pth: path.Path,
traversal_filters: List(EntryFilter),
) -> Iterator(Result(Entry, FileError)) {
iterator.once(fn() { read_directory(at: path.to_string(pth)) })
|> iterator.flat_map(fn(readdir_result) {
readdir_result
|> result.map_error(fn(e) { iterator.once(fn() { Error(e) }) })
|> result.map(fn(basenames) {
let paths =
list.map(basenames, fn(basename) { path.append_string(pth, basename) })
let #(all_entries, dir_entries) =
list.fold(paths, #([], []), fn(acc, it) {
let entry = to_entry(it)
let is_dir =
verify_is_directory(path.to_string(it))
|> result.unwrap(or: False)
#([entry, ..acc.0], case is_dir {
True -> [entry, ..acc.1]
False -> acc.1
})
})
let traverse_dirs = filter_many(dir_entries, traversal_filters)
iterator.concat([
iterator.from_list(list.map(all_entries, fn(it) { Ok(it) })),
..list.map(traverse_dirs, fn(ent) {
walk_path(path.from_string(ent.filename), traversal_filters)
})
])
})
|> result.unwrap_both
})
}