1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
#![deny(missing_docs)]
//! Coi provides an easy to use dependency injection framework.
//! Currently, this crate provides the following:
//! - **[`coi::Inject` (trait)]** - a marker trait that indicates a trait or struct is injectable.
//! - **[`coi::Provide` (trait)]** - a trait that indicates a struct is capable of providing a specific
//! implementation of some injectable trait. This is generated for you if you use
//! [`coi::Inject` (derive)] or [`coi::Provide` (derive)], but can also be written manually.
//! - **[`coi::Container`]** - a container to manage the lifetime of all dependencies. This is still
//! in its early stages, and currently only supports objects that are recreated with each request to
//! [`coi::Container::resolve`].
//! - **[`coi::ContainerBuilder`]** - a builder for the above container to simplify construction and
//! guarantee immutability after construction.
//!
//! [`coi::Inject` (trait)]: trait.Inject.html
//! [`coi::Inject` (derive)]: derive.Inject.html
//! [`coi::Provide` (trait)]: trait.Provide.html
//! [`coi::Provide` (derive)]: derive.Provide.html
//! [`coi::Container`]: struct.Container.html
//! [`coi::Container::resolve`]: struct.Container.html#method.resolve
//! [`coi::ContainerBuilder`]: struct.ContainerBuilder.html
//!
//! # Example
//!
//! ```rust
//! use coi::{container, Inject};
//! use std::sync::Arc;
//!
//! // Mark injectable traits by inheriting the `Inject` trait.
//! trait Trait1: Inject {
//!     fn describe(&self) -> &'static str;
//! }
//!
//! // For structs that will provide the implementation of an injectable trait, derive `Inject`
//! // and specify which expr will be used to inject which trait. The method can be any path.
//! // The arguments for the method are derived from fields marked with the attribute
//! // `#[coi(inject)]` (See Impl2 below).
//! #[derive(Inject)]
//! #[coi(provides dyn Trait1 with Impl1)]
//! struct Impl1;
//!
//! // Don't forget to actually implement the trait.
//! impl Trait1 for Impl1 {
//!     fn describe(&self) -> &'static str {
//!         "I'm impl1!"
//!     }
//! }
//!
//! // Mark injectable traits by inheriting the `Inject` trait.
//! trait Trait2: Inject {
//!     fn deep_describe(&self) -> String;
//! }
//!
//! // For structs that will provide the implementation of an injectable trait, derive `Inject`
//! // and specify which method will be used to inject which trait. The arguments for the method
//! // are derived from fields marked with the attribute `#[coi(inject)]`, so the parameter name
//! // must match a field name.
//! #[derive(Inject)]
//! #[coi(provides dyn Trait2 with Impl2::new(trait1))]
//! struct Impl2 {
//!     // The name of the field is important! It must match the name that's registered in the
//!     // container when the container is being built! This is similar to the behavior of
//!     // dependency injection libraries in other languages.
//!     #[coi(inject)]
//!     trait1: Arc<dyn Trait1>,
//! }
//!
//! // Implement the provider method
//! impl Impl2 {
//!     // Note: The param name here doesn't actually matter.
//!     fn new(trait1: Arc<dyn Trait1>) -> Self {
//!         Self { trait1 }
//!     }
//! }
//!
//! // Again, don't forget to actually implement the trait.
//! impl Trait2 for Impl2 {
//!     fn deep_describe(&self) -> String {
//!         format!("I'm impl2! and I have {}", self.trait1.describe())
//!     }
//! }
//!
//! // "Provider" structs are automatically generated through the `Inject` attribute. They
//! // append `Provider` to the name of the struct that is being derive (make sure you don't
//! // have any structs with the same name or your code will fail to compile.
//! // Reminder: Make sure you use the same key here as the field names of the structs that
//! // require these impls.
//! let mut container = container! {
//!     trait1 => Impl1Provider,
//!     trait2 => Impl2Provider,
//! };
//!
//! // Once the container is built, you can now resolve any particular instance by its key and
//! // the trait it provides. This crate currently only supports `Arc<dyn Trait>`, but this may
//! // be expanded in a future version of the crate.
//! let trait2 = container
//!     // Note: Getting the key wrong will produce an error telling you which key in the
//!     // chain of dependencies caused the failure (future versions might provider a vec of
//!     // chain that lead to the failure). Getting the type wrong will only tell you which key
//!     // had the wrong type. This is because at runtime, we do not have any type information,
//!     // only unique ids (that change during each compilation).
//!     .resolve::<dyn Trait2>("trait2")
//!     .expect("Should exist");
//! println!("Deep description: {}", trait2.deep_describe());
//! ```
//!
//! # How this crate works in more detail
//!
//! For any trait you wish to abstract over, have it inherit the `Inject` trait. For structs, impl
//! `Inject` for that struct, e.g.
//! ```rust
//! # use coi::Inject;
//! trait Trait1: Inject {}
//!
//! struct Struct1;
//!
//! impl Inject for Struct1 {}
//! ```
//!
//! Then, in order to register the injectable item with the [`coi::ContainerBuilder`], you also
//! need a struct that impls `Provide<Output = T>` where `T` is your trait or struct. `Provide`
//! exposes a `provide` fn that takes `&self` and `&Container`. When manually implementing `Provide`
//! you must resolve all dependencies with `container`. Here's an example below:
//!
//! ```rust
//! # use coi::{Container, Inject, Provide};
//! # use std::sync::{Arc, Mutex};
//! # trait Trait1: Inject {}
//! #
//! trait Dependency: Inject {}
//!
//! struct Impl1 {
//!     dependency: Arc<dyn Dependency>,
//! }
//!
//! impl Impl1 {
//!     fn new(dependency: Arc<dyn Dependency>) -> Self {
//!         Self { dependency }
//!     }
//! }
//!
//! impl Inject for Impl1 {}
//!
//! impl Trait1 for Impl1 {}
//!
//! struct Trait1Provider;
//!
//! impl Provide for Trait1Provider {
//!     type Output = dyn Trait1;
//!
//!     fn provide(&self, container: &Container) -> coi::Result<Arc<Self::Output>> {
//!         let dependency = container.resolve::<dyn Dependency>("dependency")?;
//!         Ok(Arc::new(Impl1::new(dependency)) as Arc<dyn Trait1>)
//!     }
//! }
//! ```
//!
//! The `"dependency"` above of course needs to be registered in order for the call
//! to `resolve` to not error out:
//!
//! ```rust
//! # use coi::{container, Container, Inject, Provide};
//! # use std::sync::Arc;
//! # trait Trait1: Inject {}
//! # trait Dependency: Inject {}
//! #
//! # struct Impl1 {
//! #     dependency: Arc<dyn Dependency>,
//! # }
//! # impl Impl1 {
//! #     fn new(dependency: Arc<dyn Dependency>) -> Self {
//! #         Self { dependency }
//! #     }
//! # }
//! # impl Inject for Impl1 {}
//! # impl Trait1 for Impl1 {}
//! #
//! # struct Trait1Provider;
//! #
//! # impl Provide for Trait1Provider {
//! #     type Output = dyn Trait1;
//! #     fn provide(&self, container: &Container) -> coi::Result<Arc<Self::Output>> {
//! #         let dependency = container.resolve::<dyn Dependency>("dependency")?;
//! #         Ok(Arc::new(Impl1::new(dependency)) as Arc<dyn Trait1>)
//! #     }
//! # }
//! struct DepImpl;
//!
//! impl Dependency for DepImpl {}
//!
//! impl Inject for DepImpl {}
//!
//! struct DependencyProvider;
//!
//! impl Provide for DependencyProvider {
//!     type Output = dyn Dependency;
//!
//!     fn provide(&self, _: &Container) -> coi::Result<Arc<Self::Output>> {
//!         Ok(Arc::new(DepImpl) as Arc<dyn Dependency>)
//!     }
//! }
//!
//! let mut container = container! {
//!     trait1 => Trait1Provider,
//!     dependency => DependencyProvider,
//! };
//! let trait1 = container.resolve::<dyn Trait1>("trait1");
//! ```
//!
//! In general, you usually won't want to write all of that. You would instead want to use the
//! procedural macro (see example above).
//! The detailed docs for that are at [`coi::Inject` (derive)]
//!
//! # Debugging
//!
//! To turn on debugging features, enable the `debug` feature (see below), then you'll have access
//! to the following changes:
//!
//! *  Formatting a container with `{:?}` will also list the dependencies (in A: Vec&lt;B&gt; style)
//! *  `Container` will get an [`analyze`] fn, which will return an error if any misconfiguration is
//! detected. See the docs for [`analyze`] for more details.
//! *  `Container` will get a [`dot_graph`] fn, which will return a string that can be passed to
//! [graphviz]'s dot command to generate a graph. The image below was generated with the sample
//! project that's in this crate's repository (output saved to `deps.dot` then ran
//! `dot -Tsvg deps.dot -o deps.svg `):
//!
//! <div>
//! <svg width="168pt" height="188pt"
//! viewBox="0.00 0.00 167.89 188.00" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
//! <g id="graph0" class="graph" transform="scale(1 1) rotate(0) translate(4 184)">
//! <title>%3</title>
//! <polygon fill="#ffffff" stroke="transparent" points="-4,4 -4,-184 163.8858,-184 163.8858,4 -4,4"/>
//! <!-- 0 -->
//! <g id="node1" class="node">
//! <title>0</title>
//! <ellipse fill="none" stroke="#000000" cx="79.9429" cy="-18" rx="67.6881" ry="18"/>
//! <text text-anchor="middle" x="79.9429" y="-14.3" font-family="Times,serif" font-size="14.00" fill="#000000">Singleton &#45; pool</text>
//! </g>
//! <!-- 1 -->
//! <g id="node2" class="node">
//! <title>1</title>
//! <ellipse fill="none" stroke="#000000" cx="79.9429" cy="-90" rx="79.8859" ry="18"/>
//! <text text-anchor="middle" x="79.9429" y="-86.3" font-family="Times,serif" font-size="14.00" fill="#000000">Scoped &#45; repository</text>
//! </g>
//! <!-- 1&#45;&gt;0 -->
//! <g id="edge1" class="edge">
//! <title>1&#45;&gt;0</title>
//! <path fill="none" stroke="#000000" d="M79.9429,-71.8314C79.9429,-64.131 79.9429,-54.9743 79.9429,-46.4166"/>
//! <polygon fill="#000000" stroke="#000000" points="83.443,-46.4132 79.9429,-36.4133 76.443,-46.4133 83.443,-46.4132"/>
//! </g>
//! <!-- 2 -->
//! <g id="node3" class="node">
//! <title>2</title>
//! <ellipse fill="none" stroke="#000000" cx="79.9429" cy="-162" rx="69.5877" ry="18"/>
//! <text text-anchor="middle" x="79.9429" y="-158.3" font-family="Times,serif" font-size="14.00" fill="#000000">Scoped &#45; service</text>
//! </g>
//! <!-- 2&#45;&gt;1 -->
//! <g id="edge2" class="edge">
//! <title>2&#45;&gt;1</title>
//! <path fill="none" stroke="#000000" d="M79.9429,-143.8314C79.9429,-136.131 79.9429,-126.9743 79.9429,-118.4166"/>
//! <polygon fill="#000000" stroke="#000000" points="83.443,-118.4132 79.9429,-108.4133 76.443,-118.4133 83.443,-118.4132"/>
//! </g>
//! </g>
//! </svg>
//! </div>
//!
//! [`analyze`]: struct.Container.html#method.analyze
//! [`dot_graph`]: struct.Container.html#method.dot_graph
//! [graphviz]: https://www.graphviz.org/
//!
//! # Features
//!
//! Compilation taking too long? Turn off features you're not using.
//!
//! To not use the default:
//! ```toml
//! # Cargo.toml
//! [dependencies]
//! coi = { version = "...", default-features = false }
//! ```
//!
//! Why the #$*%T won't my container work!?
//!
//! To turn on debugging features:
//! ```toml
//! # Cargo.toml
//! [dependencies]
//! coi = { version = "...", default-features = false, features = ["debug"] }
//! ```
//!
//! - default: `derive` - Procedural macros are re-exported.
//! - debug: `Debug` impl
//! - None - Procedural macros are not re-exported.
//!
//! # Help
//!
//! ## External traits
//!
//! Want to inject a trait that's not marked `Inject`? There's a very simple solution!
//! It works even if the intended trait is not part of your crate.
//! ```rust
//! # use coi::Inject;
//! // other.rs
//! pub trait Trait {
//! # /*
//!     ...
//! # */
//! }
//!
//! // your_lib.rs
//! # /*
//! use coi::Inject;
//! use other::Trait;
//! # */
//!
//! // Just inherit the intended trait and `Inject` on a trait in your crate,
//! // and make sure to also impl both traits for the intended provider.
//! pub trait InjectableTrait : Trait + Inject {}
//!
//! #[derive(Inject)]
//! #[coi(provides pub dyn InjectableTrait with Impl{})]
//! struct Impl {
//! # /*
//!     ...
//! # */
//! }
//!
//! impl Trait for Impl {
//! # /*
//!     ...
//! # */
//! }
//!
//! impl InjectableTrait for Impl {}
//! ```
//!
//! ## Where are the factory registrations!?
//!
//! If you're familiar with dependency injection in other languages, you might
//! be used to factory registration where you can provide a method/closure/lambda/etc.
//! during registration. Since the crate works off of the `Provide` trait, you would
//! have to manually implement `Provide` for your factory method. This would also
//! require you to manually retrieve your dependencies from the passed in `Container`
//! as shown in the docs above.
//!
//! ## Why can't I derive `Inject` when my struct contains a reference?
//!
//! In order to store all of the resolved types, we have to use
//! [`std::any::Any`], which, unfortunately, has the restriction `Any: 'static`.
//! This is because it's not yet known if there's a safe way to downcast to a
//! type with a reference (See the comments in this [tracking issue]).
//!
//! [`std::any::Any`]: https://doc.rust-lang.org/std/any/trait.Any.html
//! [tracking issue]: https://github.com/rust-lang/rust/issues/41875

use std::any::Any;
use rustc_hash::FxHashMap as HashMap;
use std::sync::{Arc, Mutex};

#[cfg(any(feature = "derive", feature = "debug"))]
pub use coi_derive::*;
#[cfg(feature = "debug")]
use petgraph::{
    algo::toposort,
    graph::{DiGraph, NodeIndex},
};
#[cfg(feature = "debug")]
use std::fmt::{self, Debug};

/// Errors produced by this crate
#[derive(Debug, thiserror::Error)]
pub enum Error {
    /// This key was not found in the container. Either the requested resource was never registered
    /// with this container, or there is a typo in the register or resolve calls.
    #[error("Key not found: {0}")]
    KeyNotFound(String),
    /// The requested key was found in the container, but its type did not match the requested type.
    #[error("Type mismatch for key: {0}")]
    TypeMismatch(String),
    /// Wrapper around errors produced by `Provider`s.
    #[error("Inner error: {0}")]
    Inner(#[from] Box<dyn std::error::Error + Send + Sync + 'static>),
}

/// Type alias to `Result<T, coi::Error>`.
pub type Result<T> = std::result::Result<T, Error>;

/// A marker trait for injectable traits and structs.
pub trait Inject: Send + Sync + 'static {}

impl<T: Inject + ?Sized> Inject for Arc<T> {}

/// Control when `Container` will call `Provide::provide`.
#[derive(Copy, Clone, Debug)]
pub enum RegistrationKind {
    /// `Container` will construct a new instance of `T` for every invocation
    /// of `Container::resolve`.
    ///
    /// # Example
    /// ```rust
    /// # use coi::{container, Inject, Result};
    /// # use std::ops::Deref;
    /// # trait Trait: Inject {}
    /// # #[derive(Inject)]
    /// # #[coi(provides dyn Trait with Impl)]
    /// # struct Impl;
    /// # impl Trait for Impl {}
    /// # fn the_test() -> Result<()> {
    /// let mut container = container! {
    ///     // same as trait => ImplProvider.transient
    ///     trait => ImplProvider
    /// };
    ///
    /// let instance_1 = container.resolve::<dyn Trait>("trait")?;
    /// let instance_2 = container.resolve::<dyn Trait>("trait")?;
    ///
    /// // Every instance resolved from the container will be a distinct instance.
    /// assert_ne!(
    ///     instance_1.deref() as &dyn Trait as *const _,
    ///     instance_2.deref() as &dyn Trait as *const _
    /// );
    /// # Ok(())
    /// # }
    /// # the_test().unwrap()
    /// ```
    Transient,
    /// `Container` will construct a new instance of `T` for each scope
    /// container created through `Container::scoped`.
    ///
    /// # Example
    /// ```rust
    /// # use coi::{container, Inject, Result};
    /// # use std::{ops::Deref, sync::{Arc, Mutex}};
    /// # trait Trait: Inject {}
    /// # #[derive(Inject)]
    /// # #[coi(provides dyn Trait with Impl)]
    /// # struct Impl;
    /// # impl Trait for Impl {}
    /// # fn the_test() -> Result<()> {
    /// let container = container! {
    ///     trait => ImplProvider.scoped
    /// };
    ///
    /// // Every instance resolved within the same scope will be the same instance.
    /// let instance_1 = container.resolve::<dyn Trait>("trait")?;
    /// let instance_2 = container.resolve::<dyn Trait>("trait")?;
    /// assert_eq!(
    ///     instance_1.deref() as &dyn Trait as *const _,
    ///     instance_2.deref() as &dyn Trait as *const _
    /// );
    /// {
    ///     let scoped = container.scoped();
    ///     let instance_3 = scoped.resolve::<dyn Trait>("trait")?;
    ///
    ///     // Since these two were resolved in different scopes, they will never be the
    ///     // same instance.
    ///     assert_ne!(
    ///         instance_1.deref() as &dyn Trait as *const _,
    ///         instance_3.deref() as &dyn Trait as *const _
    ///     );
    /// }
    /// # Ok(())
    /// # }
    /// # the_test().unwrap()
    /// ```
    Scoped,
    /// The container will construct a single instance of `T` and reuse it
    /// throughout all scopes.
    ///
    /// # Example
    /// ```rust
    /// # use coi::{container, Inject, Result};
    /// # use std::{ops::Deref, sync::{Arc, Mutex}};
    /// # trait Trait: Inject {}
    /// # #[derive(Inject)]
    /// # #[coi(provides dyn Trait with Impl)]
    /// # struct Impl;
    /// # impl Trait for Impl {}
    /// # fn the_test() -> Result<()> {
    /// let container = container! {
    ///     trait => ImplProvider.singleton
    /// };
    ///
    /// let instance_1 = container.resolve::<dyn Trait>("trait")?;
    /// let instance_2 = container.resolve::<dyn Trait>("trait")?;
    ///
    /// assert_eq!(
    ///     instance_1.deref() as &dyn Trait as *const _,
    ///     instance_2.deref() as &dyn Trait as *const _
    /// );
    /// {
    ///     let scoped = container.scoped();
    ///     let instance_3 = scoped.resolve::<dyn Trait>("trait")?;
    ///
    ///     // Regardless of what scope the instance was resolved it, it will always
    ///     // be the same instance.
    ///     assert_eq!(
    ///         instance_1.deref() as &dyn Trait as *const _,
    ///         instance_3.deref() as &dyn Trait as *const _
    ///     );
    /// }
    /// # Ok(())
    /// # }
    /// # the_test().unwrap()
    /// ```
    Singleton,
}

/// A struct used to provide a registration to a container. It wraps a registration kind and
/// a provider.
#[derive(Clone, Debug)]
pub struct Registration<T> {
    kind: RegistrationKind,
    provider: T,
}

impl<T> Registration<T> {
    /// Constructor for `Registration`. For it to be useful, `T` should impl `Provide`.
    pub fn new(kind: RegistrationKind, provider: T) -> Self {
        Self { kind, provider }
    }
}

#[derive(Clone, Debug)]
struct InnerContainer {
    provider_map: HashMap<&'static str, Registration<Arc<dyn Any + Send + Sync>>>,
    resolved_map: HashMap<&'static str, Arc<dyn Any + Send + Sync>>,
    parent: Option<Container>,
    #[cfg(feature = "debug")]
    dependency_map: HashMap<&'static str, &'static [&'static str]>,
}

impl InnerContainer {
    fn check_resolved<T>(&self, key: &'static str) -> Option<Result<Arc<T>>>
    where
        T: Inject + ?Sized,
    {
        self.resolved_map.get(key).map(|v| {
            v.downcast_ref::<Arc<T>>()
                .map(Arc::clone)
                .ok_or_else(|| Error::TypeMismatch(key.to_owned()))
        })
    }
}

/// A struct that manages all injected types.
#[derive(Clone, Debug)]
pub struct Container(Arc<Mutex<InnerContainer>>);

/// Possible errors generated when running [`Container::analyze`].
///
/// [`Container::analyze`]: struct.Container.html#method.analyze
#[cfg(feature = "debug")]
#[derive(Debug, thiserror::Error)]
pub enum AnalysisError {
    // FIXME(pfaria), it would be better if we could trace the
    // entire cycle and store a Vec<String> here. Might require
    // manually calling petgraph::visit::depth_first_search
    /// There is a cyclic dependency within the container
    #[error("Cycle detected at node `{0}`")]
    Cycle(&'static str),
    /// There is a missing dependency. Param 0 depends on Param 1, and Param 1 is missing.
    #[error("Node `{0}` depends on `{1}`, the latter of which is not registered")]
    Missing(&'static str, &'static str),
}

#[cfg(feature = "debug")]
#[derive(Clone, Default)]
struct AnalysisNode {
    registration: Option<RegistrationKind>,
    id: &'static str,
}

#[cfg(feature = "debug")]
impl fmt::Display for AnalysisNode {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self.registration {
            Some(reg) => match reg {
                RegistrationKind::Transient => write!(f, "Transient - {}", self.id),
                RegistrationKind::Singleton => write!(f, "Singleton - {}", self.id),
                RegistrationKind::Scoped => write!(f, "Scoped - {}", self.id),
            },
            None => write!(f, "MISSING - {}", self.id),
        }
    }
}

impl Container {
    fn new(container: InnerContainer) -> Self {
        Self(Arc::new(Mutex::new(container)))
    }

    /// Resolve an `Arc<T>` whose provider was previously registered with `key`.
    pub fn resolve<T>(&self, key: &'static str) -> Result<Arc<T>>
    where
        T: Inject + ?Sized,
    {
        let (kind, provider) = {
            let container = self.0.lock().unwrap();
            // If we already have a resolved version, return it.
            if let Some(resolved) = container.check_resolved::<T>(key) {
                return resolved;
            }

            // Try to find the provider
            let registration = match container.provider_map.get(key) {
                Some(provider) => provider,
                None => {
                    // If the key is not found, then we might be a child container. If we have a
                    // parent, then search it for a possibly valid provider.
                    return match &container.parent {
                        Some(parent) => {
                            let parent = parent.clone();
                            // Release the lock so we don't deadlock, this container isn't
                            // needed anymore
                            parent.resolve::<T>(key)
                        }
                        None => Err(Error::KeyNotFound(key.to_owned())),
                    };
                }
            };

            (
                registration.kind,
                registration
                    .provider
                    .downcast_ref::<Arc<dyn Provide<Output = T> + Send + Sync + 'static>>()
                    .map(Arc::clone)
                    .ok_or_else(|| Error::TypeMismatch(key.to_owned()))?,
            )
        };
        let provided = provider.provide(self);

        match kind {
            RegistrationKind::Transient => provided,
            RegistrationKind::Scoped | RegistrationKind::Singleton => {
                let mut container = self.0.lock().unwrap();
                // Since there's a possibility for a deadlock right now, we want to make sure
                // no one else already inserted into the resolved map (hence the call to entry).
                Ok(container
                    .resolved_map
                    .entry(key)
                    .or_insert(Arc::new(provided?))
                    .downcast_ref::<Arc<T>>()
                    .map(Arc::clone)
                    .unwrap())
            }
        }
    }

    /// Produce a child container that only contains providers for scoped registrations
    /// Any calls to resolve from the returned container can still use the `self` container
    /// to resolve any other kinds of registrations.
    pub fn scoped(&self) -> Container {
        let container: &InnerContainer = &self.0.lock().unwrap();
        Container::new(InnerContainer {
            provider_map: container
                .provider_map
                .iter()
                .filter_map(|(k, v)| match v.kind {
                    kind @ RegistrationKind::Scoped | kind @ RegistrationKind::Transient => Some((
                        *k,
                        Registration {
                            kind,
                            provider: Arc::clone(&v.provider),
                        },
                    )),
                    _ => None,
                })
                .collect(),
            resolved_map: HashMap::default(),
            // FIXME(pfaria) no clone here
            #[cfg(feature = "debug")]
            dependency_map: container.dependency_map.clone(),
            parent: Some(self.clone()),
        })
    }

    #[cfg(feature = "debug")]
    fn dependency_graph(&self) -> DiGraph<AnalysisNode, AnalysisNode> {
        let container = self.0.lock().unwrap();
        let mut graph = DiGraph::<AnalysisNode, AnalysisNode>::new();
        let mut key_to_node = container
            .dependency_map
            .iter()
            .map(|(k, _)| -> (&'static str, NodeIndex) {
                let kind = container.provider_map[k].kind;
                let n = graph.add_node(AnalysisNode {
                    registration: Some(kind),
                    id: k,
                });
                (k, n)
            })
            .collect::<HashMap<&str, _>>();
        for (k, deps) in &container.dependency_map {
            let kn = key_to_node[k as &str];
            let edges = deps
                .iter()
                .map(|dep| {
                    let vn = match key_to_node.get(dep) {
                        Some(vn) => *vn,
                        None => {
                            let vn = graph.add_node(AnalysisNode {
                                registration: None,
                                id: dep,
                            });
                            key_to_node.insert(dep, vn);
                            key_to_node[dep]
                        }
                    };
                    (kn, vn)
                })
                .collect::<Vec<_>>();
            graph.extend_with_edges(&edges[..]);
        }

        graph
    }

    // FIXME(pfaria): Add analysis on singleton registrations that depend on
    // non-singleton registration.
    /// Run an analysis on a container and return any issues detected.
    /// Current analysis performed:
    /// - Missing dependencies
    /// - Cyclic dependencies
    #[cfg(feature = "debug")]
    pub fn analyze(&self) -> std::result::Result<(), Vec<AnalysisError>> {
        use petgraph::Direction;
        let graph = self.dependency_graph();
        let mut errors = graph
            .node_indices()
            .filter(|i| graph[*i].registration.is_none())
            .map(|i| {
                let to = &graph[i].id;
                graph
                    .neighbors_directed(i, Direction::Incoming)
                    .map(|from| AnalysisError::Missing(graph[from].id, to))
                    .collect::<Vec<_>>()
            })
            .flatten()
            .collect::<Vec<_>>();

        // Do any cycles exist?
        if let Err(cycle) = toposort(&graph, None) {
            errors.push(AnalysisError::Cycle(graph[cycle.node_id()].id));
        }

        if errors.len() > 0 {
            Err(errors)
        } else {
            Ok(())
        }
    }

    /// Produces a dot format output that can be processed by the [graphviz] [`dot` (pdf)]
    /// program to generate a graphical representation of the dependency graph.
    ///
    /// [graphviz]: http://graphviz.org/
    /// [`dot` (pdf)]: https://graphviz.gitlab.io/_pages/pdf/dotguide.pdf
    #[cfg(feature = "debug")]
    pub fn dot_graph(&self) -> String {
        use petgraph::dot::{Config, Dot};
        let graph = self.dependency_graph();
        format!("{}", Dot::with_config(&graph, &[Config::EdgeNoLabel]))
    }
}

/// A builder used to construct a `Container`.
#[derive(Clone, Default)]
pub struct ContainerBuilder {
    provider_map: HashMap<&'static str, Registration<Arc<dyn Any + Send + Sync>>>,
    #[cfg(feature = "debug")]
    dependency_map: HashMap<&'static str, &'static [&'static str]>,
}

impl ContainerBuilder {
    /// Constructor for `ContainerBuilder`.
    pub fn new() -> Self {
        Self {
            provider_map: HashMap::default(),
            #[cfg(feature = "debug")]
            dependency_map: HashMap::default(),
        }
    }

    /// Register a `Provider` for `T` with identifier `key`.
    #[inline]
    pub fn register<P, T>(self, key: &'static str, provider: P) -> Self
    where
        T: Inject + ?Sized,
        P: Provide<Output = T> + Send + Sync + 'static,
    {
        self.register_as(
            key,
            Registration::new(RegistrationKind::Transient, provider),
        )
    }

    fn get_arc<P, T>(provider: P) -> Arc<dyn Provide<Output = T> + Send + Sync>
    where
        T: Inject + ?Sized,
        P: Provide<Output = T> + Send + Sync + 'static,
    {
        Arc::new(provider)
    }

    /// Register a `Provider` for `T` with identifier `key`, while also specifying the resolution
    /// behavior.
    pub fn register_as<P, T>(mut self, key: &'static str, registration: Registration<P>) -> Self
    where
        T: Inject + ?Sized,
        P: Provide<Output = T> + Send + Sync + 'static,
    {
        #[cfg(feature = "debug")]
        let deps = registration.provider.dependencies();
        self.provider_map.insert(
            #[cfg(feature = "debug")]
            {
                key.clone()
            },
            #[cfg(not(feature = "debug"))]
            {
                key
            },
            Registration {
                kind: registration.kind,
                provider: Arc::new(Self::get_arc(registration.provider))
                    as Arc<dyn Any + Send + Sync>,
            },
        );
        #[cfg(feature = "debug")]
        self.dependency_map.insert(key, deps);
        self
    }

    /// Consume this builder to produce a `Container`.
    pub fn build(self) -> Container {
        Container::new(InnerContainer {
            provider_map: self.provider_map,
            resolved_map: HashMap::default(),
            parent: None,
            #[cfg(feature = "debug")]
            dependency_map: self.dependency_map,
        })
    }
}

/// A trait to manage the construction of an injectable trait or struct.
pub trait Provide {
    /// The type that this provider will produce when resolved from a [`Container`].
    ///
    /// [`Container`]: struct.Container.html
    type Output: Inject + ?Sized;

    /// Only intended to be used internally
    fn provide(&self, container: &Container) -> Result<Arc<Self::Output>>;

    /// Return list of dependencies
    #[cfg(feature = "debug")]
    fn dependencies(&self) -> &'static [&'static str];
}

#[cfg(not(feature = "debug"))]
impl<T, F> Provide for F
where
    F: Fn(&Container) -> Result<Arc<T>>,
    T: Inject + ?Sized,
{
    type Output = T;

    fn provide(&self, container: &Container) -> Result<Arc<Self::Output>> {
        self(container)
    }
}

#[cfg(not(feature = "debug"))]
impl<T> Provide for dyn Fn(&Container) -> Result<Arc<T>>
where
    T: Inject + ?Sized,
{
    type Output = T;

    fn provide(&self, container: &Container) -> Result<Arc<Self::Output>> {
        self(container)
    }
}

#[cfg(featuer = "debug")]
impl<T, F> Provide for (&'static [&'static str], F)
where
    F: Fn(&Container) -> Result<Arc<T>>,
    T: Inject + ?Sized,
{
    type Output = T;

    fn provide(&self, container: &Container) -> Result<Arc<Self::Output>> {
        (self.1)(container)
    }

    fn dependencies(&self) -> &'static [&'static str] {
        self.0
    }
}

#[cfg(feature = "debug")]
impl<T> Provide
    for (
        &'static [&'static str],
        dyn Fn(&Container) -> Result<Arc<T>>,
    )
where
    T: Inject + ?Sized,
{
    type Output = T;

    fn provide(&self, container: &Container) -> Result<Arc<Self::Output>> {
        (self.1)(container)
    }

    fn dependencies(&self) -> &'static [&'static str] {
        self.0
    }
}

/// A macro to simplify building of `Container`s.
///
/// It takes a list of key-value pairs, where the keys are converted to string
/// keys, and the values are converted into registrations. Transient, singleton
/// and scoped registrations are possible, with transient being the default:
/// ```rust
/// use coi::{container, Inject};
///
/// trait Dep: Inject {}
///
/// #[derive(Inject)]
/// #[coi(provides dyn Dep with Impl)]
/// struct Impl;
///
/// impl Dep for Impl {}
///
/// let mut container = container! {
///     dep => ImplProvider,
///     transient_dep => ImplProvider; transient,
///     singleton_dep => ImplProvider; singleton,
///     scoped_dep => ImplProvider; scoped
/// };
/// ```
///
/// For details on how each registration works, see [`coi::Registration`]
///
/// [`coi::Registration`]: enum.Registration.html
#[macro_export]
macro_rules! container {
    (@registration $provider:expr; scoped) => {
        $crate::Registration::new(
            $crate::RegistrationKind::Scoped,
            $provider
        )
    };
    (@registration $provider:expr; singleton) => {
        $crate::Registration::new(
            $crate::RegistrationKind::Singleton,
            $provider
        )
    };
    (@registration $provider:expr; transient) => {
        $crate::Registration::new(
            $crate::RegistrationKind::Transient,
            $provider
        )
    };
    (@registration $provider:expr) => {
        $crate::Registration::new(
            $crate::RegistrationKind::Transient,
            $provider
        )
    };
    (@line $builder:ident $key:ident $provider:expr $(; $call:ident)?) => {
        $builder = $builder.register_as(stringify!($key), container!(@registration $provider $(; $call)?));
    };
    ($($key:ident => $provider:expr $(; $call:ident)?),+) => {
        container!{ $( $key => $provider $(; $call)?, )+ }
    };
    ($($key:ident => $provider:expr $(; $call:ident)?,)+) => {
        {
            let mut builder = ::coi::ContainerBuilder::new();
            $(container!(@line builder $key $provider $(; $call)?);)+
            builder.build()
        }
    }
}

/// Helper macro to ease use of "debug" feature when providing closures
#[macro_export]
macro_rules! provide_closure {
    // Support any comma format
    ($($move:ident)? |$($arg:ident: Arc<$ty:ty>),*| $(-> $res:ty)? $block:block) => {
        provide_closure!($($move)? |$($arg: Arc<$ty>,)*| $(-> $res)? $block)
    };
    // actual macro
    ($($move:ident)? |$($arg:ident: Arc<$ty:ty>,)*| $(-> $res:ty)? $block:block) => {
        {
            use $crate::__provide_closure_impl;
            __provide_closure_impl!($($move)? |$($arg: $ty,)*| $(-> $res)? $block)
        }
    };
    // handle case of missing argument types
    ($($move:ident)? |$($arg:ident),*| $(-> $res:ty)? $block:block) => {
        compile_error!("this macro requires closure arguments to have explicitly defined parameter types")
    };
}

#[doc(hidden)]
#[macro_export]
#[cfg(not(feature = "debug"))]
macro_rules! __provide_closure_impl {
    ($($move:ident)? |$($arg:ident: $ty:ty,)*| $(-> $res:ty)? $block:block) => {
        $($move)? |_container: &$crate::Container| $(-> $res)? {
            $(let $arg = _container.resolve::<$ty>(stringify!($arg))?;)*
            $block
        }
    };
}

#[doc(hidden)]
#[macro_export]
#[cfg(feature = "debug")]
macro_rules! __provide_closure_impl {
    ($($move:ident)? |$($arg:ident: $ty:ty,)*| $(-> $res:ty)? $block:block) => {
        (
            &[$(stringify!($arg),)*],
            $($move)? |_container: &$crate::Container| $(-> $res)? {
                $(let $arg = _container.resolve::<$ty>(stringify!($arg))?;)*
                $block
            }
        )
    };
}

#[cfg(test)]
mod test {
    use super::*;

    #[test]
    fn ensure_display() {
        use std::io;

        let error = Error::KeyNotFound("S".to_owned());
        let displayed = format!("{}", error);
        assert_eq!(displayed, "Key not found: S");

        let error = Error::TypeMismatch("S2".to_owned());
        let displayed = format!("{}", error);
        assert_eq!(displayed, "Type mismatch for key: S2");

        let error = Error::Inner(Box::new(io::Error::new(io::ErrorKind::NotFound, "oh no!")));
        let displayed = format!("{}", error);
        assert_eq!(displayed, "Inner error: oh no!");
    }

    #[test]
    fn ensure_debug() {
        let error = Error::KeyNotFound("S".to_owned());
        let debugged = format!("{:?}", error);
        assert_eq!(debugged, "KeyNotFound(\"S\")");

        let error = Error::TypeMismatch("S2".to_owned());
        let debugged = format!("{:?}", error);
        assert_eq!(debugged, "TypeMismatch(\"S2\")");
    }

    #[test]
    fn conainer_builder_is_clonable() {
        let builder = ContainerBuilder::new();
        for _ in 0..2 {
            let builder = builder.clone();
            let _container = builder.build();
        }
    }

    #[test]
    fn container_is_clonable() {
        let container = ContainerBuilder::new().build();
        let _container = container.clone();
    }
}