zammad_api/api/

knowledge_base.rs

//! Knowledge Base ("FAQ") endpoints.
//!
//! Zammad's Knowledge Base API does not hand back plain records the way the
//! ticket or user endpoints do. Instead it returns an *assets* bundle: a set of
//! id-keyed maps (`KnowledgeBaseAnswer`, `KnowledgeBaseAnswerTranslation`,
//! `KnowledgeBaseAnswerTranslationContent`, `KnowledgeBaseCategory`, ...) that
//! the caller is expected to stitch together. This module hides that stitching
//! and exposes flat [`KbAnswer`] / [`KbSearchHit`] values.
//!
//! The following operations are provided:
//!
//! - [`KnowledgeBaseApi::list`] — every answer with its title and category
//!   (no body).
//! - [`KnowledgeBaseApi::search`] — full-text search, returning highlighted
//!   title/body snippets.
//! - [`KnowledgeBaseApi::get`] — a single answer including its full body.
//! - [`KnowledgeBaseApi::create_answer`] /
//!   [`KnowledgeBaseApi::update_answer`] /
//!   [`KnowledgeBaseApi::delete_answer`] — answer writes, including the
//!   publishing state machine.
//! - [`KnowledgeBaseApi::list_knowledge_bases`] /
//!   [`KnowledgeBaseApi::list_categories`] /
//!   [`KnowledgeBaseApi::get_category`] — the structure, read from the
//!   `init` bundle.
//! - [`KnowledgeBaseApi::create_category`] /
//!   [`KnowledgeBaseApi::update_category`] /
//!   [`KnowledgeBaseApi::delete_category`] — category CRUD.
//!
//! The answer body is not part of the default `init` payload; it is fetched in
//! a second `init` call that names the wanted
//! `answer_translation_content_ids`.

use std::collections::BTreeMap;

use reqwest::Method;
use serde::Deserialize;

use crate::client::Client;
use crate::error::{Error, Result};

const INIT_PATH: &str = "api/v1/knowledge_bases/init";
const SEARCH_PATH: &str = "api/v1/knowledge_bases/search";

/// Icon used when [`NewKbCategory::icon`] is `None`; Zammad requires an
/// icon on category create.
const DEFAULT_CATEGORY_ICON: &str = "f115";

/// Knowledge Base (FAQ) endpoints.
#[derive(Debug)]
pub struct KnowledgeBaseApi<'a> {
    client: &'a Client,
}

impl<'a> KnowledgeBaseApi<'a> {
    pub(crate) fn new(client: &'a Client) -> Self {
        Self { client }
    }

    /// List every answer known to the instance, flattened to
    /// [`KbAnswer`]s (title + category, no body).
    ///
    /// `POST /api/v1/knowledge_bases/init`.
    pub async fn list(&self) -> Result<Vec<KbAnswer>> {
        let assets = self.init(&[]).await?;
        let mut answers: Vec<KbAnswer> = assets
            .answers
            .iter()
            .map(|(&id, raw)| assets.to_answer(id, raw, None))
            .collect();
        answers.sort_by_key(|a| a.id);
        Ok(answers)
    }

    /// Fetch a single answer by its numeric id, including its full body.
    ///
    /// Returns [`Error::NotFound`] when no answer with that id exists.
    ///
    /// Issues two `POST /api/v1/knowledge_bases/init` calls: one for the
    /// structure and one that requests the answer's translation content.
    pub async fn get(&self, answer_id: u64) -> Result<KbAnswer> {
        let assets = self.init(&[]).await?;
        let raw = assets.answers.get(&answer_id).ok_or(Error::NotFound)?;

        // The body lives on the translation's content record, addressed by
        // `content_id`. Ask a second `init` to include it.
        let content_id = assets.primary_translation(raw).and_then(|t| t.content_id);
        let body = self.body_of(content_id).await?;

        Ok(assets.to_answer(answer_id, raw, Some(body)))
    }

    /// Every knowledge base on the instance (from the `init` bundle).
    ///
    /// `POST /api/v1/knowledge_bases/init`.
    pub async fn list_knowledge_bases(&self) -> Result<Vec<KbInfo>> {
        let assets = self.init(&[]).await?;
        let mut kbs: Vec<KbInfo> = assets
            .kbs
            .iter()
            .map(|(&id, raw)| assets.to_kb_info(id, raw))
            .collect();
        kbs.sort_by_key(|k| k.id);
        Ok(kbs)
    }

    /// Every category of every knowledge base (from the `init` bundle),
    /// sorted by id.
    ///
    /// `POST /api/v1/knowledge_bases/init`.
    pub async fn list_categories(&self) -> Result<Vec<KbCategory>> {
        let assets = self.init(&[]).await?;
        let mut categories: Vec<KbCategory> = assets
            .categories
            .iter()
            .filter(|(_, raw)| raw.knowledge_base_id.is_some())
            .map(|(&id, raw)| assets.to_category(id, raw))
            .collect();
        categories.sort_by_key(|c| c.id);
        Ok(categories)
    }

    /// Fetch a single category by its numeric id.
    ///
    /// Returns [`Error::NotFound`] when no category with that id exists.
    ///
    /// `POST /api/v1/knowledge_bases/init`.
    pub async fn get_category(&self, category_id: u64) -> Result<KbCategory> {
        let assets = self.init(&[]).await?;
        let raw = assets.categories.get(&category_id).ok_or(Error::NotFound)?;
        Ok(assets.to_category(category_id, raw))
    }

    /// Create a category in the given knowledge base (primary locale).
    ///
    /// `kb_id` is explicit because a new category cannot be resolved from
    /// `init`. Returns [`Error::NotFound`] when the kb_id is unknown and
    /// [`Error::Config`] when the KB has no locale.
    ///
    /// `POST /api/v1/knowledge_bases/:kb_id/categories`.
    pub async fn create_category(&self, kb_id: u64, category: NewKbCategory) -> Result<KbCategory> {
        let assets = self.init(&[]).await?;
        if !assets.kbs.contains_key(&kb_id) {
            return Err(Error::NotFound);
        }
        let kb_locale_id = assets
            .primary_locale_id(kb_id)
            .ok_or_else(|| Error::Config(format!("no locale found for knowledge base {kb_id}")))?;

        let icon = category.icon.unwrap_or_else(|| DEFAULT_CATEGORY_ICON.to_string());
        let payload = serde_json::json!({
            "category_icon": icon,
            "parent_id": category.parent_id,
            "translations_attributes": [{
                "kb_locale_id": kb_locale_id,
                "title": category.title,
            }],
        });

        let path = format!("api/v1/knowledge_bases/{kb_id}/categories");
        let req = self.client.request(Method::POST, &path).json(&payload);
        let created: CategoryWriteResponse = self.client.send_json(req).await?;
        self.get_category(created.id).await
    }

    /// Partial update; kb_id resolved from the category via `init`.
    ///
    /// An all-`None` patch skips the HTTP call and returns the current
    /// state. Returns [`Error::NotFound`] when no category with that id
    /// exists.
    ///
    /// `PATCH /api/v1/knowledge_bases/:kb_id/categories/:id`.
    pub async fn update_category(&self, category_id: u64, patch: KbCategoryPatch) -> Result<KbCategory> {
        let assets = self.init(&[]).await?;
        let raw = assets.categories.get(&category_id).ok_or(Error::NotFound)?;
        if patch.title.is_none() && patch.icon.is_none() && patch.parent_id.is_none() {
            return Ok(assets.to_category(category_id, raw));
        }
        let kb_id = raw
            .knowledge_base_id
            .ok_or_else(|| Error::Config(format!("no knowledge base found for category {category_id}")))?;

        let mut payload = serde_json::json!({});
        if let Some(icon) = &patch.icon {
            payload["category_icon"] = serde_json::json!(icon);
        }
        if let Some(parent) = patch.parent_id {
            payload["parent_id"] = serde_json::json!(parent);
        }
        if let Some(title) = &patch.title {
            let translation_id = *raw
                .translation_ids
                .first()
                .ok_or_else(|| Error::Config("category has no translation to update".into()))?;
            payload["translations_attributes"] = serde_json::json!([{
                "id": translation_id,
                "title": title,
            }]);
        }

        let path = format!("api/v1/knowledge_bases/{kb_id}/categories/{category_id}");
        let req = self.client.request(Method::PATCH, &path).json(&payload);
        let _: CategoryWriteResponse = self.client.send_json(req).await?;
        self.get_category(category_id).await
    }

    /// Delete a category.
    ///
    /// Zammad refuses (422) when the category still has answers or child
    /// categories; that surfaces as [`Error::Api`].
    ///
    /// `DELETE /api/v1/knowledge_bases/:kb_id/categories/:id`.
    pub async fn delete_category(&self, category_id: u64) -> Result<()> {
        let assets = self.init(&[]).await?;
        let raw = assets.categories.get(&category_id).ok_or(Error::NotFound)?;
        let kb_id = raw
            .knowledge_base_id
            .ok_or_else(|| Error::Config(format!("no knowledge base found for category {category_id}")))?;
        let path = format!("api/v1/knowledge_bases/{kb_id}/categories/{category_id}");
        let req = self.client.request(Method::DELETE, &path);
        self.client.send_unit(req).await
    }

    /// Create a new answer in a category, in the knowledge base's primary
    /// locale.
    ///
    /// When [`NewKbAnswer::published`] is `true` a second
    /// `POST .../answers/:id/publish` call makes it public right away;
    /// otherwise it is left as a draft. The knowledge base and locale are
    /// resolved from the category.
    ///
    /// `POST /api/v1/knowledge_bases/:kb_id/answers`.
    pub async fn create_answer(&self, answer: NewKbAnswer) -> Result<KbAnswer> {
        let assets = self.init(&[]).await?;
        let kb_id = assets.kb_of_category(answer.category_id).ok_or_else(|| {
            Error::Config(format!(
                "no knowledge base found for category {}",
                answer.category_id
            ))
        })?;
        let kb_locale_id = assets
            .primary_locale_id(kb_id)
            .ok_or_else(|| Error::Config(format!("no locale found for knowledge base {kb_id}")))?;

        let payload = serde_json::json!({
            "category_id": answer.category_id,
            "translations_attributes": [{
                "title": answer.title,
                "kb_locale_id": kb_locale_id,
                "content_attributes": { "body": answer.body },
            }],
        });

        let path = format!("api/v1/knowledge_bases/{kb_id}/answers");
        let req = self.client.request(Method::POST, &path).json(&payload);
        let created: AnswerWriteResponse = self.client.send_json(req).await?;
        if answer.published {
            self.set_published(created.id, kb_id, true).await?;
        }
        self.get(created.id).await
    }

    /// Update an existing answer's title, body, and/or published state. Fields
    /// left as `None` in the [`KbAnswerPatch`] are preserved.
    ///
    /// Returns [`Error::NotFound`] when no answer with that id exists.
    ///
    /// `PATCH /api/v1/knowledge_bases/:kb_id/answers/:id`.
    pub async fn update_answer(&self, answer_id: u64, patch: KbAnswerPatch) -> Result<KbAnswer> {
        let assets = self.init(&[]).await?;
        let raw = assets.answers.get(&answer_id).ok_or(Error::NotFound)?;
        let category_id = raw
            .category_id
            .ok_or_else(|| Error::Config("answer has no category".into()))?;
        let kb_id = assets.kb_of_category(category_id).ok_or_else(|| {
            Error::Config(format!(
                "no knowledge base found for category {category_id}"
            ))
        })?;
        let kb_locale_id = assets
            .primary_locale_id(kb_id)
            .ok_or_else(|| Error::Config(format!("no locale found for knowledge base {kb_id}")))?;

        let translation_id = *raw
            .translation_ids
            .first()
            .ok_or_else(|| Error::Config("answer has no translation to update".into()))?;
        let translation = assets
            .translations
            .get(&translation_id)
            .ok_or_else(|| Error::Config("answer translation missing from payload".into()))?;
        let content_id = translation.content_id;

        // Merge: keep the current title/body for whichever field the caller
        // left unset, so a partial update never blanks the other.
        let title = match patch.title {
            Some(t) => t,
            None => translation.title.clone().unwrap_or_default(),
        };
        let body = match patch.body {
            Some(b) => b,
            None => self.body_of(content_id).await?.unwrap_or_default(),
        };

        // `content_attributes` is addressed by the translation's `id`;
        // Zammad updates the existing content in place.
        let payload = serde_json::json!({
            "category_id": category_id,
            "translations_attributes": [{
                "id": translation_id,
                "kb_locale_id": kb_locale_id,
                "title": title,
                "content_attributes": { "body": body },
            }],
        });

        let path = format!("api/v1/knowledge_bases/{kb_id}/answers/{answer_id}");
        let req = self.client.request(Method::PATCH, &path).json(&payload);
        let _: AnswerWriteResponse = self.client.send_json(req).await?;
        if let Some(published) = patch.published {
            self.set_published(answer_id, kb_id, published).await?;
        }
        self.get(answer_id).await
    }

    /// Delete an answer.
    ///
    /// The knowledge base is resolved answer → category → kb.
    ///
    /// `DELETE /api/v1/knowledge_bases/:kb_id/answers/:id`.
    pub async fn delete_answer(&self, answer_id: u64) -> Result<()> {
        let assets = self.init(&[]).await?;
        let raw = assets.answers.get(&answer_id).ok_or(Error::NotFound)?;
        let category_id = raw
            .category_id
            .ok_or_else(|| Error::Config("answer has no category".into()))?;
        let kb_id = assets.kb_of_category(category_id).ok_or_else(|| {
            Error::Config(format!(
                "no knowledge base found for category {category_id}"
            ))
        })?;
        let path = format!("api/v1/knowledge_bases/{kb_id}/answers/{answer_id}");
        let req = self.client.request(Method::DELETE, &path);
        self.client.send_unit(req).await
    }

    /// Fetch the body for a translation content id, if any.
    async fn body_of(&self, content_id: Option<u64>) -> Result<Option<String>> {
        let Some(cid) = content_id else {
            return Ok(None);
        };
        let assets = self.init(&[cid]).await?;
        Ok(assets.contents.get(&cid).and_then(|c| c.body.clone()))
    }

    /// Move an answer in the publishing state machine: `publish` makes it
    /// public, `has_publishing_update` (with all state timestamps cleared)
    /// reverts it to a draft.
    async fn set_published(&self, answer_id: u64, kb_id: u64, published: bool) -> Result<()> {
        if published {
            let path = format!("api/v1/knowledge_bases/{kb_id}/answers/{answer_id}/publish");
            let req = self.client.request(Method::POST, &path);
            self.client.send_unit(req).await
        } else {
            let path = format!(
                "api/v1/knowledge_bases/{kb_id}/answers/{answer_id}/has_publishing_update"
            );
            let body = serde_json::json!({
                "published_at": null,
                "internal_at": null,
                "archived_at": null,
            });
            let req = self.client.request(Method::POST, &path).json(&body);
            self.client.send_unit(req).await
        }
    }

    /// Full-text search across the Knowledge Base.
    ///
    /// Returns a builder; call [`SearchKnowledgeBase::send`] to run it.
    pub fn search(&self, query: impl Into<String>) -> SearchKnowledgeBase<'a> {
        SearchKnowledgeBase {
            client: self.client,
            query: query.into(),
            flavor: "public".to_string(),
            per_page: 50,
        }
    }

    /// `POST /api/v1/knowledge_bases/init`, optionally requesting the body
    /// content for the given answer-translation content ids.
    async fn init(&self, content_ids: &[u64]) -> Result<KbAssets> {
        let body = serde_json::json!({ "answer_translation_content_ids": content_ids });
        let req = self.client.request(Method::POST, INIT_PATH).json(&body);
        self.client.send_json(req).await
    }
}

/// Builder for `POST /api/v1/knowledge_bases/search`.
#[derive(Debug)]
pub struct SearchKnowledgeBase<'a> {
    client: &'a Client,
    query: String,
    flavor: String,
    per_page: u32,
}

impl SearchKnowledgeBase<'_> {
    /// Result flavor. `"public"` (the default) searches published,
    /// publicly-visible answers; `"agent"` also covers answers only visible
    /// to signed-in agents.
    pub fn flavor(mut self, flavor: impl Into<String>) -> Self {
        self.flavor = flavor.into();
        self
    }

    /// Maximum number of hits to return (default 50).
    pub fn per_page(mut self, n: u32) -> Self {
        self.per_page = n;
        self
    }

    /// Run the search.
    pub async fn send(self) -> Result<Vec<KbSearchHit>> {
        let body = serde_json::json!({
            "query": self.query,
            "flavor": self.flavor,
            "per_page": self.per_page,
            "include_subtitle": true,
        });
        let req = self.client.request(Method::POST, SEARCH_PATH).json(&body);
        let resp: SearchResponse = self.client.send_json(req).await?;

        // `details` carries the presentable fields (title, body snippet,
        // category subtitle, url); `id` there is the answer *translation* id.
        // Resolve each to its stable answer id via `init` so callers can hand
        // the id straight to [`KnowledgeBaseApi::get`].
        let hits = resp.details;
        if hits.is_empty() {
            return Ok(Vec::new());
        }

        let assets = KnowledgeBaseApi::new(self.client).init(&[]).await?;
        Ok(hits
            .into_iter()
            .map(|d| KbSearchHit {
                answer_id: assets.translations.get(&d.id).map(|t| t.answer_id),
                translation_id: d.id,
                title: strip_highlight(d.title),
                category: d.subtitle,
                snippet: strip_highlight(d.body),
                url: d.url,
            })
            .collect())
    }
}

/// A single Knowledge Base answer, flattened from Zammad's assets bundle.
#[derive(Debug, Clone)]
pub struct KbAnswer {
    /// Numeric answer id (stable; accepted by [`KnowledgeBaseApi::get`]).
    pub id: u64,
    /// Answer title, in the Knowledge Base's primary locale.
    pub title: Option<String>,
    /// Id of the category the answer belongs to.
    pub category_id: Option<u64>,
    /// Title of that category, in the primary locale.
    pub category: Option<String>,
    /// Whether the answer has been published.
    pub published: bool,
    /// The answer body (HTML). Only populated by [`KnowledgeBaseApi::get`];
    /// always `None` for [`KnowledgeBaseApi::list`].
    pub body: Option<String>,
}

/// Fields for creating a Knowledge Base answer via
/// [`KnowledgeBaseApi::create_answer`].
#[derive(Debug, Clone)]
pub struct NewKbAnswer {
    /// Category the answer belongs to. The knowledge base and locale are
    /// resolved from it.
    pub category_id: u64,
    /// Answer title.
    pub title: String,
    /// Answer body (HTML or plain text).
    pub body: String,
    /// Publish the answer immediately (`true`) or leave it a draft (`false`).
    pub published: bool,
}

/// A partial update for [`KnowledgeBaseApi::update_answer`]. Every field is
/// optional; `None` leaves the current value untouched.
#[derive(Debug, Clone, Default)]
pub struct KbAnswerPatch {
    /// New title.
    pub title: Option<String>,
    /// New body (HTML or plain text).
    pub body: Option<String>,
    /// `Some(true)` publishes, `Some(false)` reverts to a draft, `None` leaves
    /// the published state unchanged.
    pub published: Option<bool>,
}

/// A single full-text search hit.
#[derive(Debug, Clone)]
pub struct KbSearchHit {
    /// Stable answer id, resolved from the matched translation. `None` only if
    /// the translation could not be found in the structure payload.
    pub answer_id: Option<u64>,
    /// Id of the answer *translation* that matched.
    pub translation_id: u64,
    /// Answer title (search highlight markers stripped).
    pub title: Option<String>,
    /// Category the answer sits under.
    pub category: Option<String>,
    /// A snippet of the body around the match (highlight markers stripped).
    pub snippet: Option<String>,
    /// Relative help-center URL of the answer.
    pub url: Option<String>,
}

/// A knowledge base, as listed by
/// [`KnowledgeBaseApi::list_knowledge_bases`].
#[derive(Debug, Clone)]
pub struct KbInfo {
    /// Numeric knowledge base id.
    pub id: u64,
    /// Title in the KB's primary locale (from `KnowledgeBaseTranslation`),
    /// else first.
    pub title: Option<String>,
    /// Whether the knowledge base is active.
    pub active: bool,
}

/// A Knowledge Base category, flattened from Zammad's assets bundle.
#[derive(Debug, Clone)]
pub struct KbCategory {
    /// Numeric category id (stable; accepted by the category methods).
    pub id: u64,
    /// Id of the knowledge base the category belongs to.
    pub knowledge_base_id: u64,
    /// Id of the parent category, or `None` for a top-level category.
    pub parent_id: Option<u64>,
    /// FontAwesome icon code (e.g. `"f115"`).
    pub icon: Option<String>,
    /// Sort position within its parent.
    pub position: Option<u64>,
    /// Title in the KB's primary locale (first listed translation).
    pub title: Option<String>,
    /// Ids of the answers in this category.
    pub answer_ids: Vec<u64>,
    /// Ids of the direct child categories.
    pub child_ids: Vec<u64>,
    /// Creation timestamp (ISO 8601).
    pub created_at: Option<String>,
    /// Last-update timestamp (ISO 8601).
    pub updated_at: Option<String>,
}

/// Fields for creating a Knowledge Base category via
/// [`KnowledgeBaseApi::create_category`].
///
/// `icon: None` → `"f115"` (the docs' example icon; Zammad requires an
/// icon). `parent_id: None` → top-level category.
#[derive(Debug, Clone)]
pub struct NewKbCategory {
    /// Category title (primary locale).
    pub title: String,
    /// FontAwesome icon code; `None` falls back to `"f115"`.
    pub icon: Option<String>,
    /// Parent category id; `None` creates a top-level category.
    pub parent_id: Option<u64>,
}

/// A partial update for [`KnowledgeBaseApi::update_category`]. Every field is
/// optional; `None` leaves the current value untouched.
#[derive(Debug, Clone, Default)]
pub struct KbCategoryPatch {
    /// New title.
    pub title: Option<String>,
    /// New FontAwesome icon code.
    pub icon: Option<String>,
    /// Tri-state `parent_id`: `None` = unchanged, `Some(None)` = clear
    /// parent, `Some(Some(id))` = set parent.
    pub parent_id: Option<Option<u64>>,
}

// --- wire types -------------------------------------------------------------

/// The `init` assets bundle, with only the maps this module joins on.
#[derive(Debug, Default, Deserialize)]
struct KbAssets {
    #[serde(rename = "KnowledgeBaseAnswer", default)]
    answers: BTreeMap<u64, RawAnswer>,
    #[serde(rename = "KnowledgeBaseAnswerTranslation", default)]
    translations: BTreeMap<u64, RawTranslation>,
    #[serde(rename = "KnowledgeBaseAnswerTranslationContent", default)]
    contents: BTreeMap<u64, RawContent>,
    #[serde(rename = "KnowledgeBaseCategory", default)]
    categories: BTreeMap<u64, RawCategory>,
    #[serde(rename = "KnowledgeBaseCategoryTranslation", default)]
    category_translations: BTreeMap<u64, RawCategoryTranslation>,
    #[serde(rename = "KnowledgeBaseLocale", default)]
    locales: BTreeMap<u64, RawLocale>,
    #[serde(rename = "KnowledgeBase", default)]
    kbs: BTreeMap<u64, RawKb>,
    #[serde(rename = "KnowledgeBaseTranslation", default)]
    kb_translations: BTreeMap<u64, RawKbTranslation>,
}

impl KbAssets {
    /// The primary-locale translation for an answer (the first listed).
    fn primary_translation(&self, raw: &RawAnswer) -> Option<&RawTranslation> {
        raw.translation_ids
            .first()
            .and_then(|tid| self.translations.get(tid))
    }

    /// The knowledge base a category belongs to.
    fn kb_of_category(&self, category_id: u64) -> Option<u64> {
        self.categories
            .get(&category_id)
            .and_then(|c| c.knowledge_base_id)
    }

    /// The primary `kb_locale_id` of a knowledge base (needed to address a
    /// translation on write). Falls back to that KB's first locale.
    fn primary_locale_id(&self, kb_id: u64) -> Option<u64> {
        let mut first = None;
        for (&id, loc) in &self.locales {
            if loc.knowledge_base_id != kb_id {
                continue;
            }
            if loc.primary {
                return Some(id);
            }
            first.get_or_insert(id);
        }
        first
    }

    /// Build a [`KbAnswer`]. `body` is `Some(...)` for a fetched answer (the
    /// inner `Option` being whether a body actually exists), `None` for a
    /// listing where the body was never requested.
    fn to_answer(&self, id: u64, raw: &RawAnswer, body: Option<Option<String>>) -> KbAnswer {
        let title = self.primary_translation(raw).and_then(|t| t.title.clone());
        let category = raw
            .category_id
            .and_then(|cid| self.categories.get(&cid))
            .and_then(|c| c.translation_ids.first())
            .and_then(|ctid| self.category_translations.get(ctid))
            .and_then(|ct| ct.title.clone());
        KbAnswer {
            id,
            title,
            category_id: raw.category_id,
            category,
            published: raw.published_at.is_some(),
            body: body.flatten(),
        }
    }

    /// Build a [`KbCategory`]. The title is the primary-locale translation
    /// when the KB's primary locale is known, else the first listed one.
    fn to_category(&self, id: u64, raw: &RawCategory) -> KbCategory {
        KbCategory {
            id,
            knowledge_base_id: raw.knowledge_base_id.unwrap_or_default(),
            parent_id: raw.parent_id,
            icon: raw.category_icon.clone(),
            position: raw.position,
            title: self.category_title(raw),
            answer_ids: raw.answer_ids.clone(),
            child_ids: raw.child_ids.clone(),
            created_at: raw.created_at.clone(),
            updated_at: raw.updated_at.clone(),
        }
    }

    /// The category title: the translation in the KB's primary locale when
    /// both locale ids are known, else the first listed translation.
    fn category_title(&self, raw: &RawCategory) -> Option<String> {
        let primary = raw
            .knowledge_base_id
            .and_then(|kb| self.primary_locale_id(kb));
        for tid in &raw.translation_ids {
            let Some(ct) = self.category_translations.get(tid) else {
                continue;
            };
            if let (Some(ct_locale), Some(primary)) = (ct.kb_locale_id, primary) {
                if ct_locale == primary {
                    return ct.title.clone();
                }
            }
        }
        raw.translation_ids
            .first()
            .and_then(|tid| self.category_translations.get(tid))
            .and_then(|ct| ct.title.clone())
    }

    /// Build a [`KbInfo`]. The title is the `kb_translations` entry whose
    /// locale is the KB's primary one, else the first entry belonging to
    /// that KB (via its locale).
    fn to_kb_info(&self, id: u64, raw: &RawKb) -> KbInfo {
        let primary = self.primary_locale_id(id);
        let title = self
            .kb_translations
            .values()
            .find(|t| matches!((t.kb_locale_id, primary), (Some(l), Some(p)) if l == p))
            .or_else(|| {
                self.kb_translations.values().find(|t| {
                    t.kb_locale_id
                        .and_then(|l| self.locales.get(&l))
                        .is_some_and(|loc| loc.knowledge_base_id == id)
                })
            })
            .and_then(|t| t.title.clone());
        KbInfo {
            id,
            title,
            active: raw.active,
        }
    }
}

#[derive(Debug, Deserialize)]
struct RawAnswer {
    #[serde(default)]
    category_id: Option<u64>,
    #[serde(default)]
    translation_ids: Vec<u64>,
    #[serde(default)]
    published_at: Option<String>,
}

#[derive(Debug, Deserialize)]
struct RawTranslation {
    answer_id: u64,
    #[serde(default)]
    title: Option<String>,
    #[serde(default)]
    content_id: Option<u64>,
}

#[derive(Debug, Deserialize)]
struct RawContent {
    #[serde(default)]
    body: Option<String>,
}

#[derive(Debug, Deserialize)]
struct RawCategory {
    #[serde(default)]
    knowledge_base_id: Option<u64>,
    #[serde(default)]
    translation_ids: Vec<u64>,
    #[serde(default)]
    parent_id: Option<u64>,
    #[serde(default)]
    category_icon: Option<String>,
    #[serde(default)]
    position: Option<u64>,
    #[serde(default)]
    answer_ids: Vec<u64>,
    #[serde(default)]
    child_ids: Vec<u64>,
    #[serde(default)]
    created_at: Option<String>,
    #[serde(default)]
    updated_at: Option<String>,
}

#[derive(Debug, Deserialize)]
struct RawKb {
    #[serde(default)]
    active: bool,
}

#[derive(Debug, Deserialize)]
struct RawKbTranslation {
    #[serde(default)]
    title: Option<String>,
    #[serde(default)]
    kb_locale_id: Option<u64>,
}

#[derive(Debug, Deserialize)]
struct RawLocale {
    knowledge_base_id: u64,
    #[serde(default)]
    primary: bool,
}

#[derive(Debug, Deserialize)]
struct RawCategoryTranslation {
    #[serde(default)]
    title: Option<String>,
    #[serde(default)]
    kb_locale_id: Option<u64>,
}

/// The `{ id }` envelope returned by category create/update.
#[derive(Debug, Deserialize)]
struct CategoryWriteResponse {
    id: u64,
}

/// The `{ id, assets }` envelope returned by answer create/update.
#[derive(Debug, Deserialize)]
struct AnswerWriteResponse {
    id: u64,
}

#[derive(Debug, Deserialize)]
struct SearchResponse {
    #[serde(default)]
    details: Vec<SearchDetail>,
}

#[derive(Debug, Deserialize)]
struct SearchDetail {
    id: u64,
    #[serde(default)]
    title: Option<String>,
    #[serde(default)]
    body: Option<String>,
    #[serde(default)]
    subtitle: Option<String>,
    #[serde(default)]
    url: Option<String>,
}

/// Drop the `<em>…</em>` markers Zammad wraps around matched terms in search
/// highlights, leaving plain text.
fn strip_highlight(s: Option<String>) -> Option<String> {
    s.map(|s| s.replace("<em>", "").replace("</em>", ""))
}