ehds-logging 0.1.1

// SPDX-FileCopyrightText: Cadasto B.V.
// SPDX-License-Identifier: BUSL-1.1

//! The categories of one access, classified with the deployment's
//! [`CategoryMap`] from the model ids of what the access delivered, read or
//! wrote (Regulation (EU) 2025/327 Annex II 3.2(c)).
//!
//! The data an access reaches are its root objects, each named by its
//! template id and its archetype id: the template key wins, then the
//! archetype key. Where the access delivered a value that is no root object
//! (a leaf value or an aggregate), or nothing at all, the ids the request
//! constrains its data to classify it too, its templates first. A category
//! is a set, since one access reaches data of several, and `none` never
//! removes one. A key matches only exactly: an id that differs by case,
//! space or a specialisation is unmapped. Whatever is uncertain marks the
//! access [`Classification::unclassified`] with its ids as evidence, and the
//! access is never refused for it. No specification governs the
//! classification: our own design.

use std::collections::{BTreeMap, BTreeSet};
use std::fmt;

use crate::category::Category;
use crate::map::{CategoryMap, Mapping, Table};

/// What a category of an access was read from.
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
#[non_exhaustive]
pub enum Basis {
    /// A root object the access delivered or read.
    Returned,
    /// A root object the access wrote.
    Written,
    /// An id the request constrains its data to, where it carries no root
    /// object.
    Queried,
    /// The kind of request, which serves one category by construction.
    Construction,
}

impl Basis {
    /// The basis as a record writes it.
    #[must_use]
    pub fn code(self) -> &'static str {
        match self {
            Self::Returned => "returned",
            Self::Written => "written",
            Self::Queried => "queried",
            Self::Construction => "construction",
        }
    }
}

/// One root object an access reached, named by its model ids: never a value
/// it holds.
#[derive(Clone, Default, PartialEq, Eq, PartialOrd, Ord)]
pub struct RootObject {
    /// `archetype_details.template_id`, when it names one.
    pub template_id: Option<String>,
    /// `archetype_details.archetype_id`, or the archetype node id of a root.
    pub archetype_id: Option<String>,
    /// The `OBJECT_VERSION_ID` of the version the object is, when known.
    pub version_uid: Option<String>,
}

impl fmt::Debug for RootObject {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("RootObject")
            .field("template_id", &self.template_id.is_some())
            .field("archetype_id", &self.archetype_id.is_some())
            .field("version_uid", &self.version_uid.is_some())
            .finish()
    }
}

/// What an access shows of the data it reached.
#[derive(Clone, Default, PartialEq, Eq)]
pub struct Evidence {
    reached: Option<Basis>,
    objects: Vec<RootObject>,
    queried_templates: BTreeSet<String>,
    queried_archetypes: BTreeSet<String>,
    every_root_bound: bool,
    unrooted: bool,
    no_category: bool,
    unreadable: Option<Unreadable>,
    constructed: BTreeSet<Category>,
}

/// The ids a request constrains its data to, read from its syntax tree.
#[derive(Debug, Clone, Default, PartialEq, Eq)]
pub struct Queried {
    /// The template ids.
    pub templates: BTreeSet<String>,
    /// The archetype ids.
    pub archetypes: BTreeSet<String>,
    /// Whether every class the request reads data from is bound to one of
    /// them; a request the reader could not bind is never of no category.
    pub every_root_bound: bool,
}

impl Evidence {
    /// The evidence of an access that reached `objects` as `basis`
    /// ([`Basis::Returned`] or [`Basis::Written`]).
    #[must_use]
    pub fn reached(basis: Basis, objects: Vec<RootObject>) -> Self {
        Self {
            reached: Some(basis),
            objects,
            ..Self::default()
        }
    }

    /// The evidence of an access to a resource that holds no data of any
    /// category, such as an `EHR` or an `EHR_STATUS`.
    #[must_use]
    pub fn no_category() -> Self {
        Self {
            no_category: true,
            ..Self::default()
        }
    }

    /// The evidence of an access whose data could not be read for their
    /// ids, for the reason `why`.
    #[must_use]
    pub fn unreadable(why: Unreadable) -> Self {
        Self {
            unreadable: Some(why),
            ..Self::default()
        }
    }

    /// This evidence, the request constraining its data as `queried` says.
    #[must_use]
    pub fn queried(mut self, queried: Queried) -> Self {
        self.queried_templates = queried.templates;
        self.queried_archetypes = queried.archetypes;
        self.every_root_bound = queried.every_root_bound;
        self
    }

    /// This evidence, the access having delivered a value that is no root
    /// object, such as a leaf value or an aggregate, whose data the request's
    /// constraints then classify beside the root objects.
    #[must_use]
    pub fn with_unrooted(mut self) -> Self {
        self.unrooted = true;
        self
    }

    /// This evidence, the request serving `category` by construction, such
    /// as a request for a patient summary, whatever its data show: the
    /// classification holds `category` on the basis [`Basis::Construction`]
    /// beside every category the data show.
    #[must_use]
    pub fn constructed(mut self, category: Category) -> Self {
        self.constructed.insert(category);
        self
    }

    /// The root objects the access reached.
    #[must_use]
    pub fn objects(&self) -> &[RootObject] {
        &self.objects
    }
}

impl fmt::Debug for Evidence {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Evidence")
            .field("reached", &self.reached)
            .field("objects", &self.objects.len())
            .field("queried_templates", &self.queried_templates.len())
            .field("queried_archetypes", &self.queried_archetypes.len())
            .field("every_root_bound", &self.every_root_bound)
            .field("unrooted", &self.unrooted)
            .field("no_category", &self.no_category)
            .field("unreadable", &self.unreadable.is_some())
            .field("constructed", &self.constructed)
            .finish()
    }
}

/// Why an access is unclassified.
#[derive(Debug, Clone, PartialEq, Eq)]
#[non_exhaustive]
pub enum Unclassified {
    /// A root object, or every id the request names, maps to no key.
    Unmapped,
    /// The access carries no root object and the request names no id.
    NamedNothing,
    /// The request reads a class bound to no id, so what it read is not
    /// known.
    Unbound,
    /// The data could not be read for their ids, for the reason given.
    Unreadable(Unreadable),
}

impl Unclassified {
    /// The reason as a record writes it: `unmapped`, `named-nothing`,
    /// `unbound`, or the code of the [`Unreadable`] reason.
    #[must_use]
    pub fn code(&self) -> &'static str {
        match self {
            Self::Unmapped => "unmapped",
            Self::NamedNothing => "named-nothing",
            Self::Unbound => "unbound",
            Self::Unreadable(why) => why.code(),
        }
    }
}

/// Why the data of an access could not be read for their ids.
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
#[non_exhaustive]
pub enum Unreadable {
    /// The recording system does not read the data of this kind of
    /// operation: `operation-not-read`.
    Operation,
    /// The body is in a format the recording system does not read:
    /// `format-not-read`.
    Format,
    /// The body is in a format the recording system reads, but holds no
    /// root object it can name: `body-not-read`.
    Body,
    /// The access returned no object: `no-object-returned`.
    NoObject,
}

impl Unreadable {
    /// The reason as a record writes it.
    #[must_use]
    pub fn code(self) -> &'static str {
        match self {
            Self::Operation => "operation-not-read",
            Self::Format => "format-not-read",
            Self::Body => "body-not-read",
            Self::NoObject => "no-object-returned",
        }
    }
}

/// The categories of one access, their bases, and the evidence.
///
/// Only [`CategoryMap::classify`] makes one, and every one it makes holds a
/// category, is of no category by an exact `none` or a resource kind, or is
/// [`unclassified`](Classification::unclassified) with its reason: it has no
/// `Default`, so no empty classification can stand in for a missing one.
///
/// `Debug` shows the categories and the marks, never an id: a template id
/// tied to a patient says what kind of care they had.
#[derive(Clone, PartialEq, Eq)]
pub struct Classification {
    categories: BTreeMap<Category, BTreeSet<Basis>>,
    no_category: bool,
    unclassified: Option<Unclassified>,
    templates: BTreeSet<String>,
    archetypes: BTreeSet<String>,
    versions: BTreeSet<String>,
    unmapped: BTreeSet<String>,
    digest: Option<String>,
}

impl fmt::Debug for Classification {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Classification")
            .field("categories", &self.categories)
            .field("no_category", &self.no_category)
            .field("unclassified", &self.unclassified.as_ref().map(|_| "set"))
            .field("templates", &self.templates.len())
            .field("archetypes", &self.archetypes.len())
            .field("versions", &self.versions.len())
            .field("unmapped", &self.unmapped.len())
            .finish_non_exhaustive()
    }
}

impl Classification {
    /// The categories, each with what it was read from.
    #[must_use]
    pub fn categories(&self) -> &BTreeMap<Category, BTreeSet<Basis>> {
        &self.categories
    }

    /// Whether the access reached a resource of no category, or only data
    /// the map declares `none`, and nothing unclassified.
    #[must_use]
    pub fn is_no_category(&self) -> bool {
        self.no_category && self.categories.is_empty() && self.unclassified.is_none()
    }

    /// Why the access, or a part of it, is unclassified; `None` when the
    /// map classified all of it.
    #[must_use]
    pub fn unclassified(&self) -> Option<&Unclassified> {
        self.unclassified.as_ref()
    }

    /// The template ids of the evidence.
    #[must_use]
    pub fn templates(&self) -> &BTreeSet<String> {
        &self.templates
    }

    /// The archetype ids of the evidence.
    #[must_use]
    pub fn archetypes(&self) -> &BTreeSet<String> {
        &self.archetypes
    }

    /// The version uids of the root objects the access reached.
    #[must_use]
    pub fn versions(&self) -> &BTreeSet<String> {
        &self.versions
    }

    /// The ids the map holds no key for.
    #[must_use]
    pub fn unmapped(&self) -> &BTreeSet<String> {
        &self.unmapped
    }

    /// The digest of the map the access was classified under.
    #[must_use]
    pub fn digest(&self) -> Option<&str> {
        self.digest.as_deref()
    }

    fn add(&mut self, mapping: &Mapping, basis: Basis) {
        match mapping {
            Mapping::NoCategory => self.no_category = true,
            Mapping::Categories(categories) => {
                for category in categories {
                    self.categories
                        .entry(category.clone())
                        .or_default()
                        .insert(basis);
                }
            }
        }
    }
}

impl CategoryMap {
    /// The categories of an access that showed `evidence`.
    ///
    /// The categories of every root object and every queried id are joined,
    /// and `none` never removes one. The access is of no category only when
    /// its resource kind holds none, or when the map declares `none` by an
    /// exact key for everything it reached and nothing is uncertain; it is
    /// unclassified otherwise.
    #[must_use]
    pub fn classify(&self, evidence: &Evidence) -> Classification {
        let mut classified = Classification {
            categories: BTreeMap::new(),
            no_category: evidence.no_category,
            unclassified: None,
            templates: BTreeSet::new(),
            archetypes: BTreeSet::new(),
            versions: BTreeSet::new(),
            unmapped: BTreeSet::new(),
            digest: self.digest().map(str::to_owned),
        };
        if evidence.no_category {
            return classified;
        }
        if let Some(why) = evidence.unreadable {
            classified.unclassify(Unclassified::Unreadable(why));
        }
        if let Some(basis) = evidence.reached {
            for object in &evidence.objects {
                self.object(object, basis, &mut classified);
            }
        }
        for category in &evidence.constructed {
            classified
                .categories
                .entry(category.clone())
                .or_default()
                .insert(Basis::Construction);
        }
        if evidence.objects.is_empty() || evidence.unrooted {
            self.queried(evidence, &mut classified);
        }
        // NOTE: no specification governs this: our own design; a result with no category,
        // no exact `none` and no reason is a path the classifier missed, so it fails closed.
        if classified.categories.is_empty() && !classified.no_category {
            classified.unclassify(Unclassified::NamedNothing);
        }
        classified
    }

    /// Classifies one root object into `classified`: its template key, else
    /// its archetype key, else it is unmapped. An archetype's `none` does not
    /// stand for a template the map does not hold.
    fn object(&self, object: &RootObject, basis: Basis, classified: &mut Classification) {
        classified.templates.extend(object.template_id.clone());
        classified.archetypes.extend(object.archetype_id.clone());
        classified.versions.extend(object.version_uid.clone());
        let template = object
            .template_id
            .as_deref()
            .map(|template| self.template(template));
        let archetype = object
            .archetype_id
            .as_deref()
            .and_then(|archetype| self.archetype(archetype));
        let mapping = match (template, archetype) {
            (Some(Some(mapping)), _) | (None | Some(None), Some(mapping))
                if !matches!((template, mapping), (Some(None), Mapping::NoCategory)) =>
            {
                Some(mapping)
            }
            _ => None,
        };
        if let Some(mapping) = mapping {
            classified.add(mapping, basis);
            return;
        }
        classified.unmapped.extend(
            object
                .template_id
                .iter()
                .chain(&object.archetype_id)
                .cloned(),
        );
        classified.unclassify(Unclassified::Unmapped);
    }

    /// Classifies the ids the request constrains its data to: its template
    /// ids when it names any, else its archetype ids. Every one must map, and
    /// every class the request reads must be bound, or the access is
    /// unclassified beside what did map.
    fn queried(&self, evidence: &Evidence, classified: &mut Classification) {
        classified
            .templates
            .extend(evidence.queried_templates.iter().cloned());
        classified
            .archetypes
            .extend(evidence.queried_archetypes.iter().cloned());
        let (ids, table) = if evidence.queried_templates.is_empty() {
            (&evidence.queried_archetypes, Table::Archetypes)
        } else {
            (&evidence.queried_templates, Table::Templates)
        };
        if ids.is_empty() {
            classified.unclassify(Unclassified::NamedNothing);
            return;
        }
        for id in ids {
            let found = match table {
                Table::Templates => self.template(id),
                Table::Archetypes => self.archetype(id),
            };
            if let Some(mapping) = found {
                classified.add(mapping, Basis::Queried);
            } else {
                classified.unmapped.insert(id.clone());
                classified.unclassify(Unclassified::Unmapped);
            }
        }
        if !evidence.every_root_bound {
            classified.unclassify(Unclassified::Unbound);
        }
    }
}

impl Classification {
    /// Marks the access unclassified for `why`, unless a reason is held.
    fn unclassify(&mut self, why: Unclassified) {
        if self.unclassified.is_none() {
            self.unclassified = Some(why);
        }
    }
}