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#pragma once
///@file
#include <string>
#include <optional>
#include <cassert>
#include <iostream>
#include <set>
namespace nix {
/**
* A canonical representation of a path. It ensures the following:
*
* - It always starts with a slash.
*
* - It never ends with a slash, except if the path is "/".
*
* - A slash is never followed by a slash (i.e. no empty components).
*
* - There are no components equal to '.' or '..'.
*
* Note that the path does not need to correspond to an actually
* existing path, and there is no guarantee that symlinks are
* resolved.
*/
class CanonPath
{
std::string path;
public:
/**
* Construct a canon path from a non-canonical path. Any '.', '..'
* or empty components are removed.
*/
CanonPath(std::string_view raw);
explicit CanonPath(const char * raw)
: CanonPath(std::string_view(raw))
{ }
struct unchecked_t { };
CanonPath(unchecked_t _, std::string path)
: path(std::move(path))
{ }
static CanonPath fromCwd(std::string_view path = ".");
static CanonPath root;
/**
* If `raw` starts with a slash, return
* `CanonPath(raw)`. Otherwise return a `CanonPath` representing
* `root + "/" + raw`.
*/
CanonPath(std::string_view raw, const CanonPath & root);
bool isRoot() const
{ return path.size() <= 1; }
explicit operator std::string_view() const
{ return path; }
const std::string & abs() const
{ return path; }
/**
* Like abs(), but return an empty string if this path is
* '/'. Thus the returned string never ends in a slash.
*/
const std::string & absOrEmpty() const
{
const static std::string epsilon;
return isRoot() ? epsilon : path;
}
const char * c_str() const
{ return path.c_str(); }
std::string_view rel() const
{ return ((std::string_view) path).substr(1); }
struct Iterator
{
std::string_view remaining;
size_t slash;
Iterator(std::string_view remaining)
: remaining(remaining)
, slash(remaining.find('/'))
{ }
bool operator != (const Iterator & x) const
{ return remaining.data() != x.remaining.data(); }
bool operator == (const Iterator & x) const
{ return !(*this != x); }
const std::string_view operator * () const
{ return remaining.substr(0, slash); }
void operator ++ ()
{
if (slash == remaining.npos)
remaining = remaining.substr(remaining.size());
else {
remaining = remaining.substr(slash + 1);
slash = remaining.find('/');
}
}
};
Iterator begin() const { return Iterator(rel()); }
Iterator end() const { return Iterator(rel().substr(path.size() - 1)); }
std::optional<CanonPath> parent() const;
/**
* Remove the last component. Panics if this path is the root.
*/
void pop();
std::optional<std::string_view> dirOf() const
{
if (isRoot()) return std::nullopt;
return ((std::string_view) path).substr(0, path.rfind('/'));
}
std::optional<std::string_view> baseName() const
{
if (isRoot()) return std::nullopt;
return ((std::string_view) path).substr(path.rfind('/') + 1);
}
bool operator == (const CanonPath & x) const
{ return path == x.path; }
bool operator != (const CanonPath & x) const
{ return path != x.path; }
/**
* Compare paths lexicographically except that path separators
* are sorted before any other character. That is, in the sorted order
* a directory is always followed directly by its children. For
* instance, 'foo' < 'foo/bar' < 'foo!'.
*/
bool operator < (const CanonPath & x) const
{
auto i = path.begin();
auto j = x.path.begin();
for ( ; i != path.end() && j != x.path.end(); ++i, ++j) {
auto c_i = *i;
if (c_i == '/') c_i = 0;
auto c_j = *j;
if (c_j == '/') c_j = 0;
if (c_i < c_j) return true;
if (c_i > c_j) return false;
}
return i == path.end() && j != x.path.end();
}
/**
* Return true if `this` is equal to `parent` or a child of
* `parent`.
*/
bool isWithin(const CanonPath & parent) const;
CanonPath removePrefix(const CanonPath & prefix) const;
/**
* Append another path to this one.
*/
void extend(const CanonPath & x);
/**
* Concatenate two paths.
*/
CanonPath operator + (const CanonPath & x) const;
/**
* Add a path component to this one. It must not contain any slashes.
*/
void push(std::string_view c);
CanonPath operator + (std::string_view c) const;
/**
* Check whether access to this path is allowed, which is the case
* if 1) `this` is within any of the `allowed` paths; or 2) any of
* the `allowed` paths are within `this`. (The latter condition
* ensures access to the parents of allowed paths.)
*/
bool isAllowed(const std::set<CanonPath> & allowed) const;
/**
* Return a representation `x` of `path` relative to `this`, i.e.
* `CanonPath(this.makeRelative(x), this) == path`.
*/
std::string makeRelative(const CanonPath & path) const;
};
std::ostream & operator << (std::ostream & stream, const CanonPath & path);
}
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