# This file is a part of Julia. License is MIT: https://julialang.org/license

# Parse "GIT URLs" syntax (URLs and a scp-like syntax). For details see:
# https://git-scm.com/docs/git-clone#_git_urls_a_id_urls_a
# Note that using a Regex like this is inherently insecure with regards to its
# handling of passwords; we are unable to deterministically and securely erase
# the passwords from memory after use.
# TODO: reimplement with a Julian parser instead of leaning on this regex
const URL_REGEX = r"""
^(?:(?<scheme>ssh|git|https?)://)?+
(?:
    (?<user>.*?)
    (?:\:(?<password>.*?))?@
)?
(?<host>[A-Za-z0-9\-\.]+)
(?(<scheme>)
    # Only parse port when not using scp-like syntax
    (?:\:(?<port>\d+))?
    /?
    |
    :?
)
(?<path>
    # Require path to be preceded by '/'. Alternatively, ':' when using scp-like syntax.
    (?<=(?(<scheme>)/|:))
    .*
)?
$
"""x

"""
    version()::VersionNumber

Return the version of libgit2 in use, as a [`VersionNumber`](@ref man-version-number-literals).
"""
function version()
    major = Ref{Cint}(0)
    minor = Ref{Cint}(0)
    patch = Ref{Cint}(0)
    @check ccall((:git_libgit2_version, libgit2), Cint,
                 (Ref{Cint}, Ref{Cint}, Ref{Cint}), major, minor, patch)
    return VersionNumber(major[], minor[], patch[])
end
const VERSION = version()

"""
    isset(val::Integer, flag::Integer)

Test whether the bits of `val` indexed by `flag` are set (`1`) or unset (`0`).
"""
isset(val::Integer, flag::Integer) = (val & flag == flag)

"""
    reset(val::Integer, flag::Integer)

Unset the bits of `val` indexed by `flag`, returning them to `0`.
"""
reset(val::Integer, flag::Integer) = (val &= ~flag)

"""
    toggle(val::Integer, flag::Integer)

Flip the bits of `val` indexed by `flag`, so that if a bit is `0` it
will be `1` after the toggle, and vice-versa.
"""
toggle(val::Integer, flag::Integer) = (val ⊻= flag)

"""
    features()

Return a list of git features the current version of libgit2 supports, such as
threading or using HTTPS or SSH.
"""
function features()
    feat = ccall((:git_libgit2_features, libgit2), Cint, ())
    res = Consts.GIT_FEATURE[]
    for f in instances(Consts.GIT_FEATURE)
        isset(feat, Cuint(f)) && Base.push!(res, f)
    end
    return res
end

"""
    LibGit2.posixpath(path)

Standardise the path string `path` to use POSIX separators.
"""
function posixpath end
if Sys.iswindows()
    posixpath(path) = replace(path,'\\' => '/')
elseif Sys.isunix()
    posixpath(path) = path
end

"""
    LibGit2.git_url(; kwargs...)::String

Create a string based upon the URL components provided. When the `scheme` keyword is not
provided the URL produced will use the alternative [scp-like syntax](https://git-scm.com/docs/git-clone#_git_urls_a_id_urls_a).

# Keywords

  * `scheme::AbstractString=""`: the URL scheme which identifies the protocol to be used.
    For HTTP use "http", SSH use "ssh", etc. When `scheme` is not provided the output format
    will be "ssh" but using the scp-like syntax.
  * `username::AbstractString=""`: the username to use in the output if provided.
  * `password::AbstractString=""`: the password to use in the output if provided.
  * `host::AbstractString=""`: the hostname to use in the output. A hostname is required to
    be specified.
  * `port::Union{AbstractString,Integer}=""`: the port number to use in the output if
    provided. Cannot be specified when using the scp-like syntax.
  * `path::AbstractString=""`: the path to use in the output if provided.

!!! warning
    Avoid using passwords in URLs. Unlike the credential objects, Julia is not able
    to securely zero or destroy the sensitive data after use and the password may
    remain in memory; possibly to be exposed by an uninitialized memory.

# Examples
```jldoctest
julia> LibGit2.git_url(username="git", host="github.com", path="JuliaLang/julia.git")
"git@github.com:JuliaLang/julia.git"

julia> LibGit2.git_url(scheme="https", host="github.com", path="/JuliaLang/julia.git")
"https://github.com/JuliaLang/julia.git"

julia> LibGit2.git_url(scheme="ssh", username="git", host="github.com", port=2222, path="JuliaLang/julia.git")
"ssh://git@github.com:2222/JuliaLang/julia.git"
```
"""
function git_url(;
        scheme::AbstractString="",
        username::AbstractString="",
        host::AbstractString="",
        port::Union{AbstractString, Integer}="",
        path::AbstractString="")

    port_str = port isa Integer ? string(port) : port
    scp_syntax = isempty(scheme)

    isempty(host) && throw(ArgumentError("A host needs to be specified"))
    scp_syntax && !isempty(port_str) && throw(ArgumentError("Port cannot be specified when using scp-like syntax"))

    io = IOBuffer()
    !isempty(scheme) && write(io, scheme, "://")

    if !isempty(username)
        write(io, username)
        write(io, '@')
    end

    write(io, host)
    !isempty(port_str) && write(io, ':', port_str)

    if !isempty(path)
        if scp_syntax
            write(io, ':')
        elseif !startswith(path, '/')
            write(io, '/')
        end
        write(io, path)
    end
    seekstart(io)

    return takestring!(io)
end

function credential_identifier(scheme::AbstractString, host::AbstractString)
    string(isempty(scheme) ? "ssh" : scheme, "://", host)
end

function credential_identifier(url::AbstractString)
    m = match(URL_REGEX, url)
    scheme = something(m[:scheme], SubString(""))
    host = something(m[:host])
    credential_identifier(scheme, host)
end
