//! Processing a `ConfigurationTree` into a validated configuration

//!

//! This module, and particularly [`resolve`], takes care of:

//!

//!   * Deserializing a [`ConfigurationTree`] into various `FooConfigBuilder`

//!   * Calling the `build()` methods to get various `FooConfig`.

//!   * Reporting unrecognised configuration keys

//!     (eg to help the user detect misspellings).

//!

//! This is step 3 of the overall config processing,

//! as described in the [crate-level documentation](crate).

//!

//! # Starting points

//!

//! To use this, you will need to:

//!

//!   * `#[derive(Builder)]` and use [`impl_standard_builder!`](crate::impl_standard_builder)

//!     for all of your configuration structures,

//!     using `#[sub_builder]` etc. sa appropriate,

//!     and making your builders [`Deserialize`](serde::Deserialize).

//!

//!   * [`impl TopLevel`](TopLevel) for your *top level* structures (only).

//!

//!   * Call [`resolve`] (or one of its variants) with a `ConfigurationTree`,

//!     to obtain your top-level configuration(s).

//!

//! # Example

//!

//! In this example the developers are embedding `arti`, `arti_client`, etc.,

//! into a program of their own.  The example code shown:

//!

//!  * Defines a configuration structure `EmbedderConfig`,

//!    for additional configuration settings for the added features.

//!  * Establishes some configuration sources

//!    (the trivial empty `ConfigSources`, to avoid clutter in the example)

//!  * Reads those sources into a single configuration taxonomy [`ConfigurationTree`].

//!  * Processes that configuration into a 3-tuple of configuration

//!    structs for the three components, namely:

//!      - `TorClientConfig`, the configuration for the `arti_client` crate's `TorClient`

//!      - `ArtiConfig`, for behaviours in the `arti` command line utility

//!      - `EmbedderConfig`.

//!  * Will report a warning to the user about config settings found in the config files,

//!    but not recognized by *any* of the three config consumers,

//!

//! ```

//! # fn main() -> Result<(), tor_config::load::ConfigResolveError> {

//! use derive_builder::Builder;

//! use tor_config::{impl_standard_builder, resolve, ConfigBuildError, ConfigurationSources};

//! use tor_config::load::TopLevel;

//! use serde::{Deserialize, Serialize};

//!

//! #[derive(Debug, Clone, Builder, Eq, PartialEq)]

//! #[builder(build_fn(error = "ConfigBuildError"))]

//! #[builder(derive(Debug, Serialize, Deserialize))]

//! struct EmbedderConfig {

//!     // ....

//! }

//! impl_standard_builder! { EmbedderConfig }

//! impl TopLevel for EmbedderConfig {

//!     type Builder = EmbedderConfigBuilder;

//! }

//! #

//! # #[derive(Debug, Clone, Builder, Eq, PartialEq)]

//! # #[builder(build_fn(error = "ConfigBuildError"))]

//! # #[builder(derive(Debug, Serialize, Deserialize))]

//! # struct TorClientConfig { }

//! # impl_standard_builder! { TorClientConfig }

//! # impl TopLevel for TorClientConfig { type Builder = TorClientConfigBuilder; }

//! #

//! # #[derive(Debug, Clone, Builder, Eq, PartialEq)]

//! # #[builder(build_fn(error = "ConfigBuildError"))]

//! # #[builder(derive(Debug, Serialize, Deserialize))]

//! # struct ArtiConfig { }

//! # impl_standard_builder! { ArtiConfig }

//! # impl TopLevel for ArtiConfig { type Builder = ArtiConfigBuilder; }

//!

//! let cfg_sources = ConfigurationSources::new_empty(); // In real program, use from_cmdline

//! let cfg = cfg_sources.load()?;

//!

//! let (tcc, arti_config, embedder_config) =

//!      tor_config::resolve::<(TorClientConfig, ArtiConfig, EmbedderConfig)>(cfg)?;

//!

//! let _: EmbedderConfig = embedder_config; // etc.

//!

//! # Ok(())

//! # }

//! ```

use std::collections::BTreeSet;

use std::fmt::{self, Display};

use std::iter;

use std::mem;

use itertools::{chain, izip, Itertools};

use serde::de::DeserializeOwned;

use thiserror::Error;

use tracing::warn;

use crate::{ConfigBuildError, ConfigurationTree};

/// Error resolving a configuration (during deserialize, or build)

#[derive(Error, Debug)]

#[non_exhaustive]

pub enum ConfigResolveError {

    /// Deserialize failed

    #[error("Config contents not as expected")]

    Deserialize(#[from] crate::ConfigError),

    /// Build failed

    #[error("Config semantically incorrect")]

    Build(#[from] ConfigBuildError),

}

/// A type that can be built from a builder via a build method

pub trait Builder {

    /// The type that this builder constructs

    type Built;

    /// Build into a `Built`

    ///

    /// Often shadows an inherent `build` method

    fn build(&self) -> Result<Self::Built, ConfigBuildError>;

}

/// Collection of configuration settings that can be deserialized and then built

///

/// *Do not implement directly.*

/// Instead, implement [`TopLevel`]: doing so engages the blanket impl

/// for (loosely) `TopLevel + Builder`.

///

/// Each `Resolvable` corresponds to one or more configuration consumers.

///

/// Ultimately, one `Resolvable` for all the configuration consumers in an entire

/// program will be resolved from a single configuration tree (usually parsed from TOML).

///

/// Multiple config collections can be resolved from the same configuration,

/// via the implementation of `Resolvable` on tuples of `Resolvable`s.

/// Use this rather than `#[serde(flatten)]`; the latter prevents useful introspection

/// (necessary for reporting unrecognized configuration keys, and testing).

///

/// (The `resolve` method will be called only from within the `tor_config::load` module.)

pub trait Resolvable: Sized {

    /// Deserialize and build from a configuration

    //

    // Implementations must do the following:

    //

    //  1. Deserializes the input (cloning it to be able to do this)

    //     into the `Builder`.

    //

    //  2. Having used `serde_ignored` to detect unrecognized keys,

    //     intersects those with the unrecognized keys recorded in the context.

    //

    //  3. Calls `build` on the `Builder` to get `Self`.

    //

    // We provide impls for TopLevels, and tuples of Resolvable.

    //

    // Cannot be implemented outside this module (except eg as a wrapper or something),

    // because that would somehow involve creating `Self` from `ResolveContext`

    // but `ResolveContext` is completely opaque outside this module.

    fn resolve(input: &mut ResolveContext) -> Result<Self, ConfigResolveError>;

    /// Return a list of deprecated config keys, as "."-separated strings

    fn enumerate_deprecated_keys<F>(f: &mut F)

    where

        F: FnMut(&'static [&'static str]);

}

/// Top-level configuration struct, made from a deserializable builder

///

/// One configuration consumer's configuration settings.

///

/// Implementing this trait only for top-level configurations,

/// which are to be parsed at the root level of a (TOML) config file taxonomy.

///

/// This trait exists to:

///

///  * Mark the toplevel configuration structures as suitable for use with [`resolve`]

///  * Provide the type of the `Builder` for use by Rust generic code

pub trait TopLevel {

    /// The `Builder` which can be used to make a `Self`

    ///

    /// Should satisfy `&'_ Self::Builder: Builder<Built=Self>`

    type Builder: DeserializeOwned;

    /// Deprecated config keys, as "."-separates strings

    const DEPRECATED_KEYS: &'static [&'static str] = &[];

}

/// `impl Resolvable for (A,B..) where A: Resolvable, B: Resolvable ...`

///

/// The implementation simply calls `Resolvable::resolve` for each output tuple member.

///

/// `define_for_tuples!{ A B - C D.. }`

///

/// expands to

///  1. `define_for_tuples!{ A B - }`: defines for tuple `(A,B,)`

///  2. `define_for_tuples!{ A B C - D.. }`: recurses to generate longer tuples

macro_rules! define_for_tuples {

    { $( $A:ident )* - $B:ident $( $C:ident )* } => {

        define_for_tuples!{ $($A)* - }

        define_for_tuples!{ $($A)* $B - $($C)* }

    };

    { $( $A:ident )* - } => {

        impl < $($A,)* > Resolvable for ( $($A,)* )

        where $( $A: Resolvable, )*

        {

        }

    };

}

// We could avoid recursion by writing out A B C... several times (in a "triangle") but this

// would make it tiresome and error-prone to extend the impl to longer tuples.

define_for_tuples! { A - B C D E }

/// Config resolution context, not used outside `tor_config::load`

///

/// This is public only because it appears in the [`Resolvable`] trait.

/// You don't want to try to obtain one.

pub struct ResolveContext {

    /// The input

    input: ConfigurationTree,

    /// Paths unrecognized by all deserializations

    ///

    /// None means we haven't deserialized anything yet, ie means the universal set.

    ///

    /// Empty is used to disable this feature.

    unrecognized: UnrecognizedKeys,

}

/// Keys we have *not* recognized so far

///

/// Initially `AllKeys`, since we haven't recognized any.

#[derive(Debug, Clone, Hash, Eq, PartialEq, Ord, PartialOrd)]

enum UnrecognizedKeys {

    /// No keys have yet been recognized, so everything in the config is unrecognized

    AllKeys,

    /// The keys which remain unrecognized by any consumer

    ///

    /// If this is empty, we do not (need to) do any further tracking.

    These(BTreeSet<DisfavouredKey>),

}

use UnrecognizedKeys as UK;

impl UnrecognizedKeys {

    /// Does it represent the empty set

        }

    /// Update in place, intersecting with `other`

        }

    /// Remove every element of this set.

}

/// Key in config file(s) which is disfavoured (unrecognized or deprecated)

///

/// [`Display`]s in an approximation to TOML format.

/// You can use the [`to_string()`](ToString::to_string) method to obtain

/// a string containing a TOML key path.

#[derive(Debug, Clone, Hash, Eq, PartialEq, Ord, PartialOrd)]

pub struct DisfavouredKey {

    /// Can be empty only before returned from this module

    path: Vec<PathEntry>,

}

/// Element of an DisfavouredKey

#[derive(Debug, Clone, Hash, Eq, PartialEq, Ord, PartialOrd)]

enum PathEntry {

    /// Array index

    ///

    ArrayIndex(usize),

    /// Map entry

    ///

    /// string value is unquoted, needs quoting for display

    MapEntry(String),

}

/// Deserialize and build overall configuration from config sources

///

/// Inner function used by all the `resolve_*` family

                }

            }

        } else {

        },

    };

/// Deserialize and build overall configuration from config sources

///

/// Unrecognized config keys are reported as log warning messages.

///

/// Resolve the whole configuration in one go, using the `Resolvable` impl on `(A,B)`

/// if necessary, so that unrecognized config key processing works correctly.

///

/// This performs step 3 of the overall config processing,

/// as described in the [`tor_config` crate-level documentation](crate).

///

/// For an example, see the

/// [`tor_config::load` module-level documentation](self).

    let ResolutionResults {

    }

    }

/// Deserialize and build overall configuration, reporting unrecognized keys in the return value

/// Results of a successful `resolve_return_disfavoured`

#[derive(Debug, Clone)]

#[non_exhaustive]

pub struct ResolutionResults<T> {

    /// The configuration, successfully parsed

    pub value: T,

    /// Any config keys which were found in the input, but not recognized (and so, ignored)

    pub unrecognized: Vec<DisfavouredKey>,

    /// Any config keys which were found, but have been declared deprecated

    pub deprecated: Vec<DisfavouredKey>,

}

/// Deserialize and build overall configuration, silently ignoring unrecognized config keys

/// Wrapper around T that collects ignored keys as we deserialize it.

///

/// (We need a helper type here since figment does not expose a `Deserializer`

/// implementation directly.)

struct Des<T> {

    /// A set of the ignored keys that we found

    nign: BTreeSet<DisfavouredKey>,

    /// The underlying value we're deserializing.

    value: T,

}

impl<'de, T> serde::Deserialize<'de> for Des<T>

where

    T: serde::Deserialize<'de>,

{

}

impl<T> Resolvable for T

where

    T: TopLevel,

    T::Builder: Builder<Built = Self>,

{

            // If input.unrecognized.is_empty() then we don't bother tracking the

            // unrecognized keys since we would intersect with the empty set.

            // That is how this tracking is disabled when we want it to be.

            } else {

                    }

                    }

                }

            }

        };

}

/// Turns a [`serde_ignored::Path`] (which is borrowed) into an owned `DisfavouredKey`

    use serde_ignored::Path as SiP;

    use PathEntry as PE;

    loop {

        };

    }

/// Computes the intersection, resolving ignorances at different depths

///

/// Eg if `a` contains `application.wombat` and `b` contains `application`,

/// we need to return `application.wombat`.

///

/// # Formally

///

/// A configuration key (henceforth "key") is a sequence of `PathEntry`,

/// interpreted as denoting a place in a tree-like hierarchy.

///

/// Each input `BTreeSet` denotes a subset of the configuration key space.

/// Any key in the set denotes itself, but also all possible keys which have it as a prefix.

/// We say a s set is "minimal" if it doesn't have entries made redundant by this rule.

///

/// This function computes a minimal intersection of two minimal inputs.

/// If the inputs are not minimal, the output may not be either

/// (although `serde_ignored` gives us minimal sets, so that case is not important).

    // The BTreeSets produce items in sort order.

    //

    // We maintain the following invariants (valid at the top of the loop):

    //

    //   For every possible key *strictly earlier* than those remaining in either input,

    //   the output contains the key iff it was in the intersection.

    //

    //   No other keys appear in the output.

    //

    // We peek at the next two items.  The possible cases are:

    //

    //   0. One or both inputs is used up.  In that case none of any remaining input

    //      can be in the intersection and we are done.

    //

    //   1. The two inputs have the same next item.  In that case the item is in the

    //      intersection.  If the inputs are minimal, no children of that item can appear

    //      in either input, so we can make our own output minimal without thinking any

    //      more about this item from the point of view of either list.

    //

    //   2. One of the inputs is a prefix of the other.  In this case the longer item is

    //      in the intersection - as are all subsequent items from the same input which

    //      also share that prefix.  Then, we must discard the shorter item (which denotes

    //      the whole subspace of which only part is in the intersection).

    //

    //   3. Otherwise, the earlier item is definitely not in the intersection and

    //      we can munch it.

    // Peek one from each, while we can.

            // Case 0. above.

            //

            // Take the identical items off the front of both iters,

            // and put one into the output (the last will do nicely).

            //dbg!(items);

        {

            // Case 2.  One is a prefix of the other.   earlier_i is the shorter one.

            // Keep copying items from the side with the longer entries,

            // so long as they fall within (have the prefix of) the shorter entry.

            //dbg!(items, shorter_item, &prefix);

            }

            // We've "used up" the shorter item.

    }

    // Case 0.  At least one of the lists is empty, giving Err() from the array

    //for oi in &ol { eprintln!("O: {}", oi); }

impl Display for DisfavouredKey {

        use PathEntry as PE;

            // shouldn't happen with calls outside this module, and shouldn't be used inside

            // but handle it anyway

        } else {

                        } else {

                        }

                    }

                }

            }

        }

}

/// Would `s` be OK to use unquoted as a key in a TOML file?

    } else {

    }

#[cfg(test)]

#[allow(unreachable_pub)] // impl_standard_builder wants to make pub fns

mod test {

    // @@ begin test lint list maintained by maint/add_warning @@

    #![allow(clippy::bool_assert_comparison)]

    #![allow(clippy::clone_on_copy)]

    #![allow(clippy::dbg_macro)]

    #![allow(clippy::mixed_attributes_style)]

    #![allow(clippy::print_stderr)]

    #![allow(clippy::print_stdout)]

    #![allow(clippy::single_char_pattern)]

    #![allow(clippy::unwrap_used)]

    #![allow(clippy::unchecked_duration_subtraction)]

    #![allow(clippy::useless_vec)]

    #![allow(clippy::needless_pass_by_value)]

    //! <!-- @@ end test lint list maintained by maint/add_warning @@ -->

    use super::*;

    use crate::*;

    use derive_builder::Builder;

    use serde::{Deserialize, Serialize};

    fn parse_test_set(l: &[&str]) -> BTreeSet<DisfavouredKey> {

        l.iter()

            .map(|s| DisfavouredKey {

                path: s

                    .split('.')

                    .map(|s| PathEntry::MapEntry(s.into()))

                    .collect_vec(),

            })

            .collect()

    }

    #[test]

    #[rustfmt::skip] // preserve the layout so we can match vertically by eye

    fn test_intersect_unrecognized_list() {

        let chk = |a, b, exp| {

            let got = intersect_unrecognized_lists(parse_test_set(a), parse_test_set(b));

            let exp = parse_test_set(exp);

            assert_eq! { got, exp };

            let got = intersect_unrecognized_lists(parse_test_set(b), parse_test_set(a));

            assert_eq! { got, exp };

        };

        chk(&[ "a", "b",     ],

            &[ "a",      "c" ],

            &[ "a" ]);

        chk(&[ "a", "b",      "d" ],

            &[ "a",      "c", "d" ],

            &[ "a",           "d" ]);

        chk(&[ "x.a", "x.b",     ],

            &[ "x.a",      "x.c" ],

            &[ "x.a" ]);

        chk(&[ "t", "u", "v",          "w"     ],

            &[ "t",      "v.a", "v.b",     "x" ],

            &[ "t",      "v.a", "v.b",         ]);

        chk(&[ "t",      "v",              "x" ],

            &[ "t", "u", "v.a", "v.b", "w"     ],

            &[ "t",      "v.a", "v.b",         ]);

    }

    #[test]

    #[allow(clippy::bool_assert_comparison)] // much clearer this way IMO

    fn test_ok_unquoted() {

        assert_eq! { false, ok_unquoted("") };

        assert_eq! { false, ok_unquoted("_") };

        assert_eq! { false, ok_unquoted(".") };

        assert_eq! { false, ok_unquoted("-") };

        assert_eq! { false, ok_unquoted("_a") };

        assert_eq! { false, ok_unquoted(".a") };

        assert_eq! { false, ok_unquoted("-a") };

        assert_eq! { false, ok_unquoted("a.") };

        assert_eq! { true, ok_unquoted("a") };

        assert_eq! { true, ok_unquoted("1") };

        assert_eq! { true, ok_unquoted("z") };

        assert_eq! { true, ok_unquoted("aa09_-") };

    }

    #[test]

    fn test_display_key() {

        let chk = |exp, path: &[PathEntry]| {

            assert_eq! { DisfavouredKey { path: path.into() }.to_string(), exp };

        };

        let me = |s: &str| PathEntry::MapEntry(s.into());

        use PathEntry::ArrayIndex as AI;

        chk(r#""""#, &[]);

        chk(r#""@""#, &[me("@")]);

        chk(r#""\\""#, &[me(r#"\"#)]);

        chk(r#"foo"#, &[me("foo")]);

        chk(r#"foo.bar"#, &[me("foo"), me("bar")]);

        chk(r#"foo[10]"#, &[me("foo"), AI(10)]);

        chk(r#"[10].bar"#, &[AI(10), me("bar")]); // weird

    }

    #[derive(Debug, Clone, Builder, Eq, PartialEq)]

    #[builder(build_fn(error = "ConfigBuildError"))]

    #[builder(derive(Debug, Serialize, Deserialize))]

    struct TestConfigA {

        #[builder(default)]

        a: String,

    }

    impl_standard_builder! { TestConfigA }

    impl TopLevel for TestConfigA {

        type Builder = TestConfigABuilder;

    }

    #[derive(Debug, Clone, Builder, Eq, PartialEq)]

    #[builder(build_fn(error = "ConfigBuildError"))]

    #[builder(derive(Debug, Serialize, Deserialize))]

    struct TestConfigB {

        #[builder(default)]

        b: String,

        #[builder(default)]

        old: bool,

    }

    impl_standard_builder! { TestConfigB }

    impl TopLevel for TestConfigB {

        type Builder = TestConfigBBuilder;

        const DEPRECATED_KEYS: &'static [&'static str] = &["old"];

    }

    #[test]

    fn test_resolve() {

        let test_data = r#"

            wombat = 42

            a = "hi"

            old = true

        "#;

        let cfg = {

            let mut sources = crate::ConfigurationSources::new_empty();

            sources.push_source(

                crate::ConfigurationSource::from_verbatim(test_data.to_string()),

                crate::sources::MustRead::MustRead,

            );

            sources.load().unwrap()

        };

        let _: (TestConfigA, TestConfigB) = resolve_ignore_warnings(cfg.clone()).unwrap();

        let resolved: ResolutionResults<(TestConfigA, TestConfigB)> =

            resolve_return_results(cfg).unwrap();

        let (a, b) = resolved.value;

        let mk_strings =

            |l: Vec<DisfavouredKey>| l.into_iter().map(|ik| ik.to_string()).collect_vec();

        let ign = mk_strings(resolved.unrecognized);

        let depr = mk_strings(resolved.deprecated);

        assert_eq! { &a, &TestConfigA { a: "hi".into() } };

        assert_eq! { &b, &TestConfigB { b: "".into(), old: true } };

        assert_eq! { ign, &["wombat"] };

        assert_eq! { depr, &["old"] };

        let _ = TestConfigA::builder();

        let _ = TestConfigB::builder();

    }

    #[derive(Debug, Clone, Builder, Eq, PartialEq)]

    #[builder(build_fn(error = "ConfigBuildError"))]

    #[builder(derive(Debug, Serialize, Deserialize))]

    struct TestConfigC {

        #[builder(default)]

        c: u32,

    }

    impl_standard_builder! { TestConfigC }

    impl TopLevel for TestConfigC {

        type Builder = TestConfigCBuilder;

    }

    #[test]

    fn build_error() {

        // Make sure that errors are propagated correctly.

        let test_data = r#"

            # wombat is not a number.

            c = "wombat"

            # this _would_ be unrecognized, but for the errors.

            persimmons = "sweet"

        "#;

        // suppress a dead-code warning.

        let _b = TestConfigC::builder();

        let cfg = {

            let mut sources = crate::ConfigurationSources::new_empty();

            sources.push_source(

                crate::ConfigurationSource::from_verbatim(test_data.to_string()),

                crate::sources::MustRead::MustRead,

            );

            sources.load().unwrap()

        };

        {

            // First try "A", then "C".

            let res1: Result<ResolutionResults<(TestConfigA, TestConfigC)>, _> =

                resolve_return_results(cfg.clone());

            assert!(res1.is_err());

            assert!(matches!(res1, Err(ConfigResolveError::Deserialize(_))));

        }

        {

            // Now the other order: first try "C", then "A".

            let res2: Result<ResolutionResults<(TestConfigC, TestConfigA)>, _> =

                resolve_return_results(cfg.clone());

            assert!(res2.is_err());

            assert!(matches!(res2, Err(ConfigResolveError::Deserialize(_))));

        }

        // Try manually, to make sure unrecognized fields are removed.

        let mut ctx = ResolveContext {

            input: cfg,

            unrecognized: UnrecognizedKeys::AllKeys,

        };

        let _res3 = TestConfigA::resolve(&mut ctx);

        // After resolving A, some fields are unrecognized.

        assert!(matches!(&ctx.unrecognized, UnrecognizedKeys::These(k) if !k.is_empty()));

        {

            let res4 = TestConfigC::resolve(&mut ctx);

            assert!(matches!(res4, Err(ConfigResolveError::Deserialize(_))));

        }

        {

            // After resolving C with an error, the unrecognized-field list is cleared.

            assert!(matches!(&ctx.unrecognized, UnrecognizedKeys::These(k) if k.is_empty()));

        }

    }

}