const std = @import("std");
const fmt = std.fmt;
const mem = std.mem;
const math = std.math;
const sort = std.sort;
const unicode = std.unicode;
const Allocator = std.mem.Allocator;
const ArrayListUnmanaged = std.ArrayListUnmanaged;
const ArrayList = std.ArrayList;
const MultiArrayList = std.MultiArrayList;
const StringHashMap = std.StringHashMap;
const AutoHashMap = std.AutoHashMap;
const BufSet = std.BufSet;

const pad = @import("padding.zig");
const compress = @import("compress.zig");
const shellImport = @import("shell.zig");
const userImport = @import("user.zig");
const groupImport = @import("group.zig");
const cmph = @import("cmph.zig");
const bdz = @import("bdz.zig");
const User = userImport.User;
const Group = groupImport.Group;
const ShellSections = shellImport.ShellWriter.ShellSections;
const ShellReader = shellImport.ShellReader;

const Corpus = struct {
    arena: std.heap.ArenaAllocator,

    // sorted by name, by unicode codepoint
    users: MultiArrayList(User),
    // sorted by gid
    groups: MultiArrayList(Group),

    name2user: StringHashMap(u32),
    name2group: StringHashMap(u32),
    group2users: []const []const u32,
    user2groups: []const []const u32,

    pub fn init(
        baseAllocator: Allocator,
        usersConst: []const User,
        groupsConst: []const Group,
    ) error{ OutOfMemory, InvalidUtf8, Duplicate, NotFound }!Corpus {
        var arena = std.heap.ArenaAllocator.init(baseAllocator);
        var allocator = arena.allocator();
        errdefer arena.deinit();

        var users_arr = try allocator.alloc(User, usersConst.len);
        var groups_arr = try allocator.alloc(Group, groupsConst.len);
        for (usersConst) |*user, i|
            users_arr[i] = try user.clone(allocator);
        for (groupsConst) |*group, i|
            groups_arr[i] = try group.clone(allocator);

        sort.sort(User, users_arr, {}, cmpUser);
        sort.sort(Group, groups_arr, {}, cmpGroup);

        var users = MultiArrayList(User){};
        try users.ensureTotalCapacity(allocator, users_arr.len);
        for (users_arr) |user|
            users.appendAssumeCapacity(user);
        var groups = MultiArrayList(Group){};
        try groups.ensureTotalCapacity(allocator, groups_arr.len);
        for (groups_arr) |group|
            groups.appendAssumeCapacity(group);

        var name2user = StringHashMap(u32).init(allocator);
        var name2group = StringHashMap(u32).init(allocator);
        for (users.items(.name)) |name, i| {
            var res1 = try name2user.getOrPut(name);
            if (res1.found_existing)
                return error.Duplicate;
            res1.value_ptr.* = @intCast(u32, i);
        }

        for (groups.items(.name)) |name, i| {
            var res1 = try name2group.getOrPut(name);
            if (res1.found_existing)
                return error.Duplicate;
            res1.value_ptr.* = @intCast(u32, i);
        }

        var group2users = try allocator.alloc([]u32, groups.len);

        // uses baseAllocator, because it will be freed before
        // returning from this function. This keeps the arena clean.
        var user2groups = try baseAllocator.alloc(ArrayListUnmanaged(u32), users.len);
        defer baseAllocator.free(user2groups);
        mem.set(ArrayListUnmanaged(u32), user2groups, ArrayListUnmanaged(u32){});

        for (groups.items(.members)) |group_members, i| {
            var members = try allocator.alloc(u32, group_members.count());
            members.len = 0;

            var it = group_members.iterator();
            while (it.next()) |memberName| {
                if (name2user.get(memberName.*)) |user_idx| {
                    members.len += 1;
                    members[members.len - 1] = user_idx;
                    try user2groups[user_idx].append(allocator, @intCast(u32, i));
                } else return error.NotFound;
            }

            group2users[i] = members;
        }

        for (group2users) |*groupusers|
            sort.sort(u32, groupusers.*, {}, comptime sort.asc(u32));

        var user2groups_final = try allocator.alloc([]const u32, users.len);
        user2groups_final.len = users.len;
        for (user2groups) |*usergroups, i| {
            sort.sort(u32, usergroups.items, {}, comptime sort.asc(u32));
            user2groups_final[i] = usergroups.toOwnedSlice(allocator);
        }

        return Corpus{
            .arena = arena,
            .users = users,
            .groups = groups,
            .name2user = name2user,
            .name2group = name2group,
            .group2users = group2users,
            .user2groups = user2groups_final,
        };
    }

    pub fn deinit(self: *Corpus) void {
        self.arena.deinit();
        self.* = undefined;
    }
};

pub fn shellSections(
    allocator: Allocator,
    corpus: *const Corpus,
) error{ OutOfMemory, Overflow }!ShellSections {
    var popcon = shellImport.ShellWriter.init(allocator);
    for (corpus.users.items(.shell)) |shell|
        try popcon.put(shell);
    return popcon.toOwnedSections(shellImport.max_shells);
}

pub const UserGids = struct {
    // user index -> offset in blob
    idx2offset: []const u64,
    // compressed user gids blob. A blob contains N <= users.len items,
    // an item is:
    //   len: varint
    //   gid: [varint]varint,
    // ... and the gid list is delta-compressed.
    blob: []const u8,

    pub fn deinit(self: *UserGids, allocator: Allocator) void {
        allocator.free(self.idx2offset);
        allocator.free(self.blob);
        self.* = undefined;
    }
};

pub fn userGids(
    allocator: Allocator,
    corpus: *const Corpus,
) error{ OutOfMemory, Overflow }!UserGids {
    var blob = ArrayList(u8).init(allocator);
    errdefer blob.deinit();
    var idx2offset = try allocator.alloc(u64, corpus.users.len);
    errdefer allocator.free(idx2offset);

    // zero'th entry is empty, so groupless users can refer to it.
    try compress.appendUvarint(&blob, 0);

    var scratch = try allocator.alloc(u32, 256);
    defer allocator.free(scratch);
    for (corpus.user2groups) |usergroups, user_idx| {
        if (usergroups.len == 0) {
            idx2offset[user_idx] = 0;
            continue;
        }
        idx2offset[user_idx] = blob.items.len;
        scratch = try allocator.realloc(scratch, usergroups.len);
        scratch.len = usergroups.len;
        const corpusGids = corpus.groups.items(.gid);
        for (usergroups) |group_idx, i|
            scratch[i] = corpusGids[group_idx];
        compress.deltaCompress(u32, scratch) catch |err| switch (err) {
            error.NotSorted => unreachable,
        };
        try compress.appendUvarint(&blob, usergroups.len);
        for (scratch) |gid|
            try compress.appendUvarint(&blob, gid);
    }

    return UserGids{
        .idx2offset = idx2offset,
        .blob = blob.toOwnedSlice(),
    };
}

pub const UsersSection = struct {
    // user index -> offset in blob
    idx2offset: []const u32,
    blob: []const u8,

    pub fn deinit(self: *UsersSection, allocator: Allocator) void {
        allocator.free(self.idx2offset);
        allocator.free(self.blob);
        self.* = undefined;
    }
};

pub fn usersSection(
    allocator: Allocator,
    corpus: *const Corpus,
    gids: *const UserGids,
    shells: *const ShellSections,
) error{ OutOfMemory, Overflow, InvalidRecord }!UsersSection {
    var idx2offset = try allocator.alloc(u32, corpus.users.len);
    errdefer allocator.free(idx2offset);
    // as of writing each user takes 12 bytes + blobs + padding, padded to
    // 8 bytes. 24 is an optimistic lower bound for an average record size.
    var blob = try ArrayList(u8).initCapacity(allocator, 24 * corpus.users.len);
    errdefer blob.deinit();
    var i: usize = 0;
    while (i < corpus.users.len) : (i += 1) {
        // TODO: this is inefficient; it's calling `.slice()` on every iteration
        const user = corpus.users.get(i);
        const user_offset = try math.cast(u32, blob.items.len);
        std.debug.assert(user_offset & 7 == 0);
        idx2offset[i] = user_offset;
        try userImport.PackedUser.packTo(
            &blob,
            user,
            gids.idx2offset[i],
            shells.indices,
        );
        try pad.arrayList(&blob, userImport.PackedUser.alignment_bits);
    }
    return UsersSection{
        .idx2offset = idx2offset,
        .blob = blob.toOwnedSlice(),
    };
}

pub const GroupMembers = struct {
    // group index to it's offset in blob
    idx2offset: []const u64,
    // members are delta-varint encoded byte-offsets to the user struct
    blob: []const u8,

    pub fn deinit(self: *GroupMembers, allocator: Allocator) void {
        allocator.free(self.idx2offset);
        allocator.free(self.blob);
        self.* = undefined;
    }
};

pub fn groupMembers(
    allocator: Allocator,
    corpus: *const Corpus,
    user2offset: []const u32,
) error{OutOfMemory}!GroupMembers {
    var idx2offset = try allocator.alloc(u64, corpus.groups.len);
    errdefer allocator.free(idx2offset);
    var blob = ArrayList(u8).init(allocator);
    errdefer blob.deinit();
    // zero'th entry is empty, so empty groups can refer to it
    try compress.appendUvarint(&blob, 0);

    var scratch = try ArrayList(u32).initCapacity(allocator, 1024);
    defer scratch.deinit();

    for (corpus.group2users) |members, group_idx| {
        if (members.len == 0) {
            idx2offset[group_idx] = 0;
            continue;
        }

        idx2offset[group_idx] = blob.items.len;
        try scratch.ensureTotalCapacity(members.len);
        scratch.items.len = members.len;
        for (members) |user_idx, i|
            scratch.items[i] = user2offset[user_idx];

        compress.deltaCompress(u32, scratch.items) catch |err| switch (err) {
            error.NotSorted => unreachable,
        };
        try compress.appendUvarint(&blob, members.len);
        for (scratch.items) |elem|
            try compress.appendUvarint(&blob, elem);
    }
    return GroupMembers{
        .idx2offset = idx2offset,
        .blob = blob.toOwnedSlice(),
    };
}

pub const GroupsSection = struct {
    // group index -> offset in blob
    idx2offset: []const u32,
    blob: []const u8,

    pub fn deinit(self: *GroupsSection, allocator: Allocator) void {
        allocator.free(self.idx2offset);
        allocator.free(self.blob);
        self.* = undefined;
    }
};

pub fn groupsSection(
    allocator: Allocator,
    corpus: *const Corpus,
    members_offset: []const u64,
) error{ OutOfMemory, Overflow, InvalidRecord }!GroupsSection {
    var idx2offset = try allocator.alloc(u32, corpus.groups.len);
    errdefer allocator.free(idx2offset);

    var blob = try ArrayList(u8).initCapacity(allocator, 8 * corpus.groups.len);
    errdefer blob.deinit();

    var i: usize = 0;
    while (i < corpus.groups.len) : (i += 1) {
        // TODO: this is inefficient; it's calling `.slice()` on every iteration
        const group = corpus.groups.get(i);
        const group_offset = try math.cast(u32, blob.items.len);
        std.debug.assert(group_offset & 7 == 0);
        idx2offset[i] = group_offset;
        const group_stored = groupImport.GroupStored{
            .gid = group.gid,
            .name = group.name,
            .members_offset = members_offset[i],
        };
        try groupImport.PackedGroup.packTo(&blob, group_stored);
        try pad.arrayList(&blob, groupImport.PackedGroup.alignment_bits);
    }

    return GroupsSection{
        .idx2offset = idx2offset,
        .blob = blob.toOwnedSlice(),
    };
}

// creates a bdz index using packed_mphf. buf[bdz_search(key)] = index(keys, key)
pub fn bdzIdx(
    comptime T: type,
    allocator: Allocator,
    packed_mphf: []const u8,
    keys: []const T,
) error{OutOfMemory}![]const u32 {
    const search_fn = comptime blk: {
        switch (T) {
            u32 => break :blk bdz.search_u32,
            []const u8 => break :blk bdz.search,
            else => unreachable,
        }
    };
    std.debug.assert(keys.len <= math.maxInt(u32));
    var result = try allocator.alloc(u32, keys.len);
    for (keys) |key, i| {
        const hash = search_fn(packed_mphf, key);
        result[hash] = @intCast(u32, i);
    }
    return result;
}

// cmpUser compares two users for sorting. By username's utf8 codepoints, ascending.
fn cmpUser(_: void, a: User, b: User) bool {
    var utf8_a = (unicode.Utf8View.init(a.name) catch unreachable).iterator();
    var utf8_b = (unicode.Utf8View.init(b.name) catch unreachable).iterator();
    while (utf8_a.nextCodepoint()) |codepoint_a| {
        if (utf8_b.nextCodepoint()) |codepoint_b| {
            if (codepoint_a == codepoint_b) {
                continue;
            } else return codepoint_a < codepoint_b;
        }

        // a is a prefix of b. It is thus shorter.
        return false;
    }
    // b is a prefix of a
    return true;
}

fn cmpGroup(_: void, a: Group, b: Group) bool {
    return a.gid < b.gid;
}

pub const AllSections = struct {
    allocator: Allocator,

    bdz_gid: []const u8,
    bdz_groupname: []const u8,
    bdz_uid: []const u8,
    bdz_username: []const u8,
    users: UsersSection,
    shell_sections: ShellSections,
    shell_reader: ShellReader,
    user_gids: UserGids,
    group_members: GroupMembers,
    groups: GroupsSection,
    idx_gid2group: []const u32,
    idx_groupname2group: []const u32,
    idx_uid2user: []const u32,
    idx_name2user: []const u32,

    pub fn init(
        allocator: Allocator,
        corpus: *const Corpus,
    ) error{ Overflow, OutOfMemory, InvalidRecord }!AllSections {
        const bdz_gid = try cmph.packU32(allocator, corpus.groups.items(.gid));
        const bdz_groupname = try cmph.packStr(allocator, corpus.groups.items(.name));
        const bdz_uid = try cmph.packU32(allocator, corpus.users.items(.uid));
        const bdz_username = try cmph.packStr(allocator, corpus.users.items(.name));
        const shell_sections = try shellSections(allocator, corpus);
        const user_gids = try userGids(allocator, corpus);
        const users = try usersSection(
            allocator,
            corpus,
            &user_gids,
            &shell_sections,
        );
        const group_members = try groupMembers(
            allocator,
            corpus,
            users.idx2offset,
        );
        const groups = try groupsSection(
            allocator,
            corpus,
            group_members.idx2offset,
        );
        const shell_reader = shellImport.ShellReader.init(
            mem.sliceAsBytes(shell_sections.index.constSlice()),
            mem.sliceAsBytes(shell_sections.blob.constSlice()),
        );

        var idx_gid2group = try bdzIdx(
            u32,
            allocator,
            bdz_gid,
            corpus.groups.items(.gid),
        );
        var idx_groupname2group = try bdzIdx(
            []const u8,
            allocator,
            bdz_groupname,
            corpus.groups.items(.name),
        );
        var idx_uid2user = try bdzIdx(
            u32,
            allocator,
            bdz_uid,
            corpus.users.items(.uid),
        );
        var idx_name2user = try bdzIdx(
            []const u8,
            allocator,
            bdz_username,
            corpus.users.items(.name),
        );

        return AllSections{
            .allocator = allocator,
            .bdz_gid = bdz_gid,
            .bdz_groupname = bdz_groupname,
            .bdz_uid = bdz_uid,
            .bdz_username = bdz_username,
            .shell_sections = shell_sections,
            .shell_reader = shell_reader,
            .user_gids = user_gids,
            .users = users,
            .group_members = group_members,
            .groups = groups,
            .idx_gid2group = idx_gid2group,
            .idx_groupname2group = idx_groupname2group,
            .idx_uid2user = idx_uid2user,
            .idx_name2user = idx_name2user,
        };
    }

    pub fn deinit(self: *AllSections) void {
        self.allocator.free(self.bdz_gid);
        self.allocator.free(self.bdz_groupname);
        self.allocator.free(self.bdz_uid);
        self.allocator.free(self.bdz_username);
        self.shell_sections.deinit();
        self.user_gids.deinit(self.allocator);
        self.users.deinit(self.allocator);
        self.group_members.deinit(self.allocator);
        self.groups.deinit(self.allocator);
        self.allocator.free(self.idx_gid2group);
        self.allocator.free(self.idx_groupname2group);
        self.allocator.free(self.idx_uid2user);
        self.allocator.free(self.idx_name2user);
        self.* = undefined;
    }
};

const testing = std.testing;

fn testCorpus(allocator: Allocator) !Corpus {
    const users = [_]User{ User{
        .uid = 128,
        .gid = 128,
        .name = "vidmantas",
        .gecos = "Vidmantas Kaminskas",
        .home = "/home/vidmantas",
        .shell = "/bin/bash",
    }, User{
        .uid = 0,
        .gid = math.maxInt(u32),
        .name = "Name" ** 8,
        .gecos = "Gecos" ** 51,
        .home = "Home" ** 16,
        .shell = "She.LllL" ** 8,
    }, User{
        .uid = 1002,
        .gid = 1002,
        .name = "svc-bar",
        .gecos = "",
        .home = "/",
        .shell = "/",
    }, User{
        .uid = 65534,
        .gid = 65534,
        .name = "nobody",
        .gecos = "nobody",
        .home = "/nonexistent",
        .shell = "/usr/sbin/nologin",
    } };

    var members1 = try groupImport.someMembers(
        allocator,
        &[_][]const u8{"vidmantas"},
    );
    defer members1.deinit();

    var members2 = try groupImport.someMembers(
        allocator,
        &[_][]const u8{ "svc-bar", "vidmantas" },
    );
    defer members2.deinit();

    var members3 = try groupImport.someMembers(
        allocator,
        &[_][]const u8{ "svc-bar", "Name" ** 8, "vidmantas" },
    );
    defer members3.deinit();

    const groups = [_]Group{ Group{
        .gid = 128,
        .name = "vidmantas",
        .members = members1,
    }, Group{
        .gid = 9999,
        .name = "all",
        .members = members3,
    }, Group{
        .gid = 0,
        .name = "service-account",
        .members = members2,
    } };

    return try Corpus.init(allocator, users[0..], groups[0..]);
}

test "test corpus" {
    var corpus = try testCorpus(testing.allocator);
    defer corpus.deinit();

    const name_name = 0;
    const nobody = 1;
    const svc_bar = 2;
    const vidmantas = 3;

    const usernames = corpus.users.items(.name);
    try testing.expectEqualStrings(usernames[name_name], "Name" ** 8);
    try testing.expectEqualStrings(usernames[nobody], "nobody");
    try testing.expectEqualStrings(usernames[svc_bar], "svc-bar");
    try testing.expectEqualStrings(usernames[vidmantas], "vidmantas");

    const g_service_account = 0;
    const g_vidmantas = 1;
    const g_all = 2;

    const groupnames = corpus.groups.items(.name);
    try testing.expectEqualStrings(groupnames[g_service_account], "service-account");
    try testing.expectEqualStrings(groupnames[g_vidmantas], "vidmantas");
    try testing.expectEqualStrings(groupnames[g_all], "all");

    try testing.expectEqual(corpus.name2user.get("404"), null);
    try testing.expectEqual(corpus.name2user.get("vidmantas").?, vidmantas);
    try testing.expectEqual(corpus.name2group.get("404"), null);
    try testing.expectEqual(corpus.name2group.get("vidmantas").?, g_vidmantas);

    const membersOfAll = corpus.group2users[g_all];
    try testing.expectEqual(membersOfAll[0], name_name);
    try testing.expectEqual(membersOfAll[1], svc_bar);
    try testing.expectEqual(membersOfAll[2], vidmantas);

    const groupsOfVidmantas = corpus.user2groups[vidmantas];
    try testing.expectEqual(groupsOfVidmantas[0], g_service_account);
    try testing.expectEqual(groupsOfVidmantas[1], g_vidmantas);
    try testing.expectEqual(groupsOfVidmantas[2], g_all);
}

test "test groups, group members and users" {
    const allocator = testing.allocator;
    var corpus = try testCorpus(allocator);
    defer corpus.deinit();

    var sections = try AllSections.init(allocator, &corpus);
    defer sections.deinit();

    const blob = sections.group_members.blob;
    var i: usize = 0;
    while (i < corpus.groups.len) : (i += 1) {
        const offset = sections.group_members.idx2offset[i];
        var vit = try compress.VarintSliceIterator(blob[offset..]);
        var it = compress.DeltaDecompressionIterator(&vit);
        for (corpus.group2users[i]) |user_idx| {
            const got_user_offset = (try it.next()).?;
            const want_user_offset = sections.users.idx2offset[user_idx];
            try testing.expectEqual(got_user_offset, want_user_offset);
        }
        try testing.expectEqual(it.next(), null);
    }

    var it = userImport.PackedUser.iterator(
        sections.users.blob,
        sections.shell_reader,
    );
    i = 0;
    while (i < corpus.users.len) : (i += 1) {
        const got = (try it.next()).?;
        const user = corpus.users.get(i);
        try testing.expectEqual(user.uid, got.uid());
        try testing.expectEqual(user.gid, got.gid());
        try testing.expectEqualStrings(user.name, got.name());
        try testing.expectEqualStrings(user.gecos, got.gecos());
        try testing.expectEqualStrings(user.home, got.home());
        try testing.expectEqualStrings(user.shell, got.shell(sections.shell_reader));
    }
}

test "userGids" {
    const allocator = testing.allocator;
    var corpus = try testCorpus(allocator);
    defer corpus.deinit();

    var user_gids = try userGids(allocator, &corpus);
    defer user_gids.deinit(allocator);

    var user_idx: usize = 0;
    while (user_idx < corpus.users.len) : (user_idx += 1) {
        const groups = corpus.user2groups[user_idx];
        const offset = user_gids.idx2offset[user_idx];
        if (groups.len == 0) {
            try testing.expect(offset == 0);
            continue;
        }
        var vit = try compress.VarintSliceIterator(user_gids.blob[offset..]);
        var it = compress.DeltaDecompressionIterator(&vit);
        try testing.expectEqual(it.remaining(), groups.len);
        var i: u64 = 0;
        const corpusGids = corpus.groups.items(.gid);
        while (try it.next()) |gid| : (i += 1) {
            try testing.expectEqual(gid, corpusGids[groups[i]]);
        }
        try testing.expectEqual(i, groups.len);
    }
}

test "pack gids" {
    const allocator = testing.allocator;
    var corpus = try testCorpus(allocator);
    defer corpus.deinit();

    const cmph_gid = try cmph.packU32(allocator, corpus.groups.items(.gid));
    defer allocator.free(cmph_gid);

    const k1 = bdz.search_u32(cmph_gid, 0);
    const k2 = bdz.search_u32(cmph_gid, 128);
    const k3 = bdz.search_u32(cmph_gid, 9999);
    var hashes = &[_]u32{ k1, k2, k3 };
    sort.sort(u32, hashes, {}, comptime sort.asc(u32));
    for (hashes) |hash, i|
        try testing.expectEqual(i, hash);
}

fn testUser(name: []const u8) User {
    var result = std.mem.zeroes(User);
    result.name = name;
    return result;
}

test "users compare function" {
    const a = testUser("a");
    const b = testUser("b");
    const bb = testUser("bb");
    try testing.expect(cmpUser({}, a, b));
    try testing.expect(!cmpUser({}, b, a));
    try testing.expect(cmpUser({}, a, bb));
    try testing.expect(!cmpUser({}, bb, a));
    try testing.expect(cmpUser({}, b, bb));
    try testing.expect(!cmpUser({}, bb, b));
}

test "bdzIdx" {
    const allocator = testing.allocator;
    const k_u32 = [_]u32{ 42, 1, 2, 3 };
    const k_str = [_][]const u8{ "42", "1", "2", "3" };
    const mphf_str = try cmph.packStr(allocator, k_str[0..]);
    const mphf_u32 = try cmph.packU32(allocator, k_u32[0..]);
    defer allocator.free(mphf_str);
    defer allocator.free(mphf_u32);

    {
        var result = try bdzIdx(u32, allocator, mphf_u32, k_u32[0..]);
        defer allocator.free(result);
        var used = [_]bool{false} ** 4;
        for (result) |elem| used[result[elem]] = true;
        for (used) |item| try testing.expect(item);
    }

    {
        var result = try bdzIdx([]const u8, allocator, mphf_str, k_str[0..]);
        defer allocator.free(result);
        var used = [_]bool{false} ** 4;
        for (result) |elem| used[result[elem]] = true;
        for (used) |item| try testing.expect(item);
    }
}