/*
 * Copyright (C) 2026 Mateusz Gruszczyński @linuxiarz.pl
 * Source-Available Code / Dual-Licensed.
 *
 * Free for non-commercial and evaluation use under terms of BSL/GPLv3.
 * Commercial or production use requires a valid paid license.
 * See LICENSE file in repository root for details.
 */

use super::*;

#[derive(Debug, Deserialize)]
pub struct CreatePadRequest {
    name: String,
    #[serde(default)]
    password: Option<String>,
    #[serde(default)]
    content: Option<String>,
}

#[derive(Debug, Deserialize)]
pub struct SetPadPasswordRequest {
    password: String,
    #[serde(default)]
    client_id: Option<String>,
}

#[derive(Debug, Serialize)]
pub struct CreatePadResponse {
    slug: String,
    url: String,
}

#[derive(Debug, Serialize)]
pub struct PadInfo {
    slug: String,
    title: String,
    protected: bool,
    access_level: String,
    allow_public_task_updates: bool,
    public_page_unprotected: bool,
    public_page_enabled: bool,
    private: bool,
    created_at: String,
    updated_at: String,
    can_delete_files: bool,
    can_upload_files: bool,
    upload_max_size_bytes: Option<usize>,
    global_color: Option<String>,
    note_color: Option<String>,
    authorship_mode: String,
    colors_enabled: bool,
    compact_view: bool,
    editor_line_numbers: bool,
    preview_line_numbers: bool,
    line_links: bool,
    toolbar_collapsed: bool,
    navbar_collapsed: bool,
    font_family: String,
    font_size: i64,
    personal_editor_settings: bool,
    can_save_editor_settings: bool,
    can_manage_authorship: bool,
    can_set_password: bool,
    files: Vec<MarkdownFileReference>,
}

pub async fn create_pad(
    State(state): State<SharedState>,
    headers: HeaderMap,
    Json(payload): Json<CreatePadRequest>,
) -> Result<(StatusCode, Json<CreatePadResponse>), ApiError> {
    let title = validate_name(&payload.name, "Note name")?;
    let password = validate_password(payload.password.as_deref())?;
    let initial_content = validate_initial_content(payload.content.as_deref())?;
    let base = slugify(title);
    if base.is_empty() {
        return Err(ApiError::bad_request(
            "The name cannot be converted into a valid address",
        ));
    }
    let slug = unique_pad_slug(&state, &base).await?;
    let account_user = crate::auth::optional_user(&state, &headers)
        .await
        .map_err(|e| ApiError::forbidden(&e.message))?;
    let author = account_user.as_ref().map(|user| user.nickname.clone());
    let created_by_guest_id = if account_user.is_none() {
        requester_guest_id(&headers)
    } else {
        None
    };
    let pad = db::create_pad(&state.db, &slug, title, password, created_by_guest_id).await?;
    if let Some(user) = account_user.as_ref() {
        sqlx::query(queries::get(state.db.kind(), queries::USER_ATTACH_PAD))
            .bind(user.id)
            .bind(&pad.slug)
            .execute(state.db.pool())
            .await?;
    }
    if let Some(content) = initial_content {
        db::save_pad_revision(&state.db, pad.id, content, author.as_deref(), "[]").await?;
    }
    Ok((
        StatusCode::CREATED,
        Json(CreatePadResponse {
            url: format!("/p/{slug}"),
            slug,
        }),
    ))
}

pub async fn pad_info(
    State(state): State<SharedState>,
    headers: HeaderMap,
    Path(slug): Path<String>,
) -> Result<Json<PadInfo>, ApiError> {
    let pad = db::find_pad(&state.db, &slug)
        .await?
        .ok_or_else(ApiError::not_found_note)?;
    ensure_private_resource_access(&state, &headers, "pad", &pad.slug, pad.is_private).await?;
    let access_level = effective_header_access_level(
        &state,
        &headers,
        "pad",
        &pad.slug,
        pad.is_private,
        pad.password_hash.is_some(),
    )
    .await?;
    let (global_color, note_color) = editor_colors(&state, &headers, "pad", &slug).await?;
    let (editor_preferences, personal_editor_settings) =
        user_editor_preferences(&state, &headers, db::EditorPreferenceResource::Pad(pad.id))
            .await?;
    let resource_editor_settings =
        db::load_resource_editor_settings(&state.db, "pad", &slug).await?;
    let account_owner =
        crate::auth::is_resource_owner(&state, "pad", &slug, user_session_token(&headers))
            .await
            .unwrap_or(false);
    let guest_owner = pad_creator_is_requester(&headers, &pad);
    let password_write_access = has_password_write_access(&state, &headers, "pad", &slug).await?;
    let can_manage_authorship =
        can_manage_resource_settings(account_owner, guest_owner, password_write_access);
    let upload_max_size_bytes = resource_upload_limit(&state, &headers, "pad", &slug).await?;
    let can_upload_files = upload_max_size_bytes.is_some();
    let can_save_editor_settings = (personal_editor_settings || can_manage_authorship)
        && has_write_permission(&state, &headers, "pad", &slug).await?;
    if pad.is_private == 0
        && pad.password_hash.is_some()
        && !db::pad_public_page_disabled(&state.db, pad.id).await?
        && !db::pad_public_page_enabled(&state.db, pad.id).await?
    {
        db::publish_pad(&state.db, pad.id).await?;
    }
    Ok(Json(PadInfo {
        slug: pad.slug,
        title: pad.title,
        protected: pad.password_hash.is_some(),
        access_level: access_level_name(access_level).into(),
        allow_public_task_updates: db::pad_public_task_updates(&state.db, pad.id).await?,
        public_page_unprotected: db::pad_public_page_unprotected(&state.db, pad.id).await?,
        public_page_enabled: db::pad_public_page_enabled(&state.db, pad.id).await?,
        private: pad.is_private != 0,
        created_at: db::normalize_timestamp(&pad.created_at),
        updated_at: db::normalize_timestamp(&pad.updated_at),
        can_delete_files: can_manage_authorship,
        can_upload_files,
        upload_max_size_bytes,
        global_color,
        note_color,
        authorship_mode: resource_editor_settings.authorship_mode,
        colors_enabled: resource_editor_settings.colors_enabled,
        compact_view: editor_preferences.compact_view,
        editor_line_numbers: editor_preferences.editor_line_numbers,
        preview_line_numbers: editor_preferences.preview_line_numbers,
        line_links: editor_preferences.line_links,
        toolbar_collapsed: editor_preferences.toolbar_collapsed,
        navbar_collapsed: editor_preferences.navbar_collapsed,
        font_family: editor_preferences.font_family,
        font_size: editor_preferences.font_size,
        personal_editor_settings,
        can_save_editor_settings,
        can_manage_authorship,
        can_set_password: can_set_resource_password(
            pad.password_hash.is_some(),
            account_owner,
            guest_owner,
        ),
        files: markdown_file_references(&state, Some(pad.id), None, None).await?,
    }))
}

pub async fn set_pad_password(
    State(state): State<SharedState>,
    headers: HeaderMap,
    Path(slug): Path<String>,
    Json(payload): Json<SetPadPasswordRequest>,
) -> Result<Json<serde_json::Value>, ApiError> {
    let pad = db::find_pad(&state.db, &slug)
        .await?
        .ok_or_else(ApiError::not_found_note)?;
    if pad.password_hash.is_some() {
        return Err(ApiError::bad_request("This note already has a password."));
    }
    let account_owner = crate::auth::is_resource_owner(
        &state, "pad", &slug, user_session_token(&headers),
    ).await.unwrap_or(false);
    let guest_owner = pad_creator_is_requester(&headers, &pad);
    if !can_set_resource_password(pad.password_hash.is_some(), account_owner, guest_owner) {
        return Err(ApiError::forbidden("Only the note owner can set its password."));
    }
    let except_client_id =
        crate::websocket::clean_collaboration_client_id(payload.client_id);
    let password = validate_password(Some(payload.password.as_str()))?
        .ok_or_else(|| ApiError::bad_request("Password is required."))?;
    db::set_pad_password(&state.db, &slug, password).await?;
    state
        .notify_pad_password_required(&slug, except_client_id)
        .await;
    Ok(Json(serde_json::json!({"ok": true, "protected": true})))
}

pub async fn set_pad_editor_settings(
    State(state): State<SharedState>,
    headers: HeaderMap,
    Path(slug): Path<String>,
    Json(payload): Json<EditorSettingsRequest>,
) -> Result<Json<serde_json::Value>, ApiError> {
    let pad = db::find_pad(&state.db, &slug)
        .await?
        .ok_or_else(ApiError::not_found_note)?;
    let creator_can_manage_authorship = can_manage_resource_settings(
        false,
        pad_creator_is_requester(&headers, &pad),
        has_password_write_access(&state, &headers, "pad", &slug).await?,
    );
    save_editor_settings(
        &state,
        &headers,
        "pad",
        &slug,
        "pad",
        &slug,
        db::EditorPreferenceResource::Pad(pad.id),
        creator_can_manage_authorship,
        payload,
    )
    .await
}

pub async fn pad_editor_color(
    State(state): State<SharedState>,
    headers: HeaderMap,
    Path(slug): Path<String>,
) -> Result<Json<serde_json::Value>, ApiError> {
    let (global_color, note_color) = editor_colors(&state, &headers, "pad", &slug).await?;
    Ok(Json(
        serde_json::json!({"global_color": global_color, "note_color": note_color}),
    ))
}

pub async fn note_editor_color(
    State(state): State<SharedState>,
    headers: HeaderMap,
    Path((workspace_slug, note_slug)): Path<(String, String)>,
) -> Result<Json<serde_json::Value>, ApiError> {
    let (global_color, note_color) = editor_colors(
        &state,
        &headers,
        "note",
        &format!("{}/{}", workspace_slug, note_slug),
    )
    .await?;
    Ok(Json(
        serde_json::json!({"global_color": global_color, "note_color": note_color}),
    ))
}

pub async fn set_pad_editor_color(
    State(state): State<SharedState>,
    headers: HeaderMap,
    Path(slug): Path<String>,
    Json(payload): Json<EditorColorRequest>,
) -> Result<Json<serde_json::Value>, ApiError> {
    save_editor_color(&state, &headers, "pad", &slug, payload.color.as_deref()).await
}

pub async fn set_note_editor_color(
    State(state): State<SharedState>,
    headers: HeaderMap,
    Path((workspace_slug, note_slug)): Path<(String, String)>,
    Json(payload): Json<EditorColorRequest>,
) -> Result<Json<serde_json::Value>, ApiError> {
    save_editor_color(
        &state,
        &headers,
        "note",
        &format!("{}/{}", workspace_slug, note_slug),
        payload.color.as_deref(),
    )
    .await
}

pub async fn publish_pad_page(
    State(state): State<SharedState>,
    headers: HeaderMap,
    Path(slug): Path<String>,
    Json(payload): Json<PublishRequest>,
) -> Result<Json<PublishResponse>, ApiError> {
    let pad = authorized_pad(
        &state,
        &slug,
        payload.password.as_deref(),
        resource_request_token(&headers, "pad", &slug, payload.access_token.as_deref()),
        bearer_token(&headers),
        &headers,
    )
    .await?;
    let level = if db::verify_pad_password(&pad, payload.password.as_deref())
        || (pad.is_private == 0 && pad.password_hash.is_none())
    {
        AccessLevel::Write
    } else {
        request_access_level(
            &state,
            &headers,
            "pad",
            &slug,
            resource_request_token(&headers, "pad", &slug, payload.access_token.as_deref()),
            bearer_token(&headers),
        )
        .await?
    };
    require_write(level)?;
    let enabled = payload.enabled.unwrap_or(true);
    if enabled && pad.password_hash.is_none() {
        return Err(ApiError::bad_request(
            "Set a resource password before enabling the published page.",
        ));
    }
    if !enabled {
        db::unpublish_pad(&state.db, pad.id).await?;
        db::set_pad_public_page_disabled(&state.db, pad.id, true).await?;
        return Ok(Json(PublishResponse {
            url: None,
            enabled: false,
        }));
    }
    db::set_pad_public_page_disabled(&state.db, pad.id, false).await?;
    let token = db::publish_pad(&state.db, pad.id).await?;
    db::set_pad_public_task_updates(&state.db, pad.id, payload.allow_task_updates).await?;
    db::set_pad_public_page_unprotected(&state.db, pad.id, payload.unprotect_page).await?;
    Ok(Json(PublishResponse {
        url: Some(format!("/s/{token}")),
        enabled: true,
    }))
}

pub async fn publish_note_page(
    State(state): State<SharedState>,
    headers: HeaderMap,
    Path((workspace_slug, note_slug)): Path<(String, String)>,
    Json(payload): Json<PublishRequest>,
) -> Result<Json<PublishResponse>, ApiError> {
    let (workspace, note) = authorized_note(
        &state,
        &workspace_slug,
        &note_slug,
        payload.password.as_deref(),
        resource_request_token(
            &headers,
            "workspace",
            &workspace_slug,
            payload.access_token.as_deref(),
        ),
        bearer_token(&headers),
        &headers,
    )
    .await?;
    let level = if db::verify_workspace_password(&workspace, payload.password.as_deref())
        || (workspace.is_private == 0 && workspace.password_hash.is_none())
    {
        AccessLevel::Write
    } else {
        request_access_level(
            &state,
            &headers,
            "workspace",
            &workspace_slug,
            resource_request_token(
                &headers,
                "workspace",
                &workspace_slug,
                payload.access_token.as_deref(),
            ),
            bearer_token(&headers),
        )
        .await?
    };
    require_write(level)?;
    let enabled = payload.enabled.unwrap_or(true);
    if enabled && workspace.password_hash.is_none() {
        return Err(ApiError::bad_request(
            "Set a workspace password before enabling the published page.",
        ));
    }
    if !enabled {
        db::unpublish_note(&state.db, note.id).await?;
        db::set_note_public_page_disabled(&state.db, note.id, true).await?;
        return Ok(Json(PublishResponse {
            url: None,
            enabled: false,
        }));
    }
    db::set_note_public_page_disabled(&state.db, note.id, false).await?;
    let token = db::publish_note(&state.db, note.id).await?;
    db::set_note_public_task_updates(&state.db, note.id, payload.allow_task_updates).await?;
    db::set_note_public_page_unprotected(&state.db, note.id, payload.unprotect_page).await?;
    Ok(Json(PublishResponse {
        url: Some(format!("/s/{token}")),
        enabled: true,
    }))
}

fn page_password(headers: &HeaderMap) -> Option<&str> {
    headers
        .get("x-rustpad-page-password")
        .and_then(|value| value.to_str().ok())
        .map(str::trim)
        .filter(|value| !value.is_empty())
}

async fn ensure_public_page_access(
    state: &SharedState,
    headers: &HeaderMap,
    page: &db::PublishedPage,
) -> Result<(), ApiError> {
    let password = page_password(headers);
    if let Some(pad_id) = page.pad_id {
        let page_unprotected = db::pad_public_page_unprotected(&state.db, pad_id).await?;
        let sql = match state.db.kind() {
            crate::database::DatabaseKind::Postgres => "SELECT slug FROM pads WHERE id = $1",
            _ => "SELECT slug FROM pads WHERE id = ?",
        };
        let slug: Option<String> = sqlx::query_scalar(sql)
            .bind(pad_id)
            .fetch_optional(state.db.pool())
            .await?;
        let Some(slug) = slug else {
            return Err(ApiError::not_found_note());
        };
        let pad = db::find_pad(&state.db, &slug)
            .await?
            .ok_or_else(ApiError::not_found_note)?;
        if pad.password_hash.is_none() {
            return Err(ApiError::forbidden(
                "This published page is unavailable until a resource password is set.",
            ));
        }
        if page_unprotected || has_header_resource_access(state, headers, "pad", &slug).await? {
            return Ok(());
        }
        let password_ok = db::verify_pad_password(&pad, password);
        check_resource_password_attempt(state, headers, "pad", &slug, password, password_ok)
            .await?;
        if password_ok {
            return Ok(());
        }
        return if pad.password_hash.is_some() {
            Err(ApiError::forbidden("Password required or incorrect."))
        } else {
            Err(ApiError::forbidden("This published page is protected."))
        };
    }
    if let Some(note_id) = page.note_id {
        let page_unprotected = db::note_public_page_unprotected(&state.db, note_id).await?;
        let sql = match state.db.kind() {
            crate::database::DatabaseKind::Postgres => {
                "SELECT w.slug FROM notes n JOIN workspaces w ON w.id = n.workspace_id WHERE n.id = $1"
            }
            _ => {
                "SELECT w.slug FROM notes n JOIN workspaces w ON w.id = n.workspace_id WHERE n.id = ?"
            }
        };
        let slug: Option<String> = sqlx::query_scalar(sql)
            .bind(note_id)
            .fetch_optional(state.db.pool())
            .await?;
        let Some(slug) = slug else {
            return Err(ApiError::not_found_note());
        };
        let workspace = db::find_workspace(&state.db, &slug)
            .await?
            .ok_or_else(ApiError::not_found_workspace)?;
        if workspace.password_hash.is_none() {
            return Err(ApiError::forbidden(
                "This published page is unavailable until a workspace password is set.",
            ));
        }
        if page_unprotected
            || has_header_resource_access(state, headers, "workspace", &slug).await?
        {
            return Ok(());
        }
        let password_ok = db::verify_workspace_password(&workspace, password);
        check_resource_password_attempt(state, headers, "workspace", &slug, password, password_ok)
            .await?;
        if password_ok {
            return Ok(());
        }
        return if workspace.password_hash.is_some() {
            Err(ApiError::forbidden("Password required or incorrect."))
        } else {
            Err(ApiError::forbidden("This published page is protected."))
        };
    }
    Err(ApiError::not_found_note())
}

pub async fn public_page(
    State(state): State<SharedState>,
    headers: HeaderMap,
    Path(token): Path<String>,
) -> Result<Json<PublicPageResponse>, ApiError> {
    let page = db::find_published_page(&state.db, &token)
        .await?
        .ok_or_else(ApiError::not_found_note)?;
    ensure_public_page_access(&state, &headers, &page).await?;
    let files =
        markdown_file_references(&state, page.pad_id, page.note_id, Some(&page.content)).await?;
    Ok(Json(PublicPageResponse {
        title: page.title,
        content: page.content,
        updated_at: db::normalize_timestamp(&page.updated_at),
        allow_task_updates: page.allow_task_updates,
        files,
    }))
}

async fn commit_public_pad_task_update(
    state: &SharedState,
    page: &db::PublishedPage,
    source_line: usize,
    checked: bool,
) -> Result<(), ApiError> {
    let pad_id = page.pad_id.ok_or_else(ApiError::not_found_note)?;
    let room_key = crate::state::AppState::pad_room_key(&page.resource_slug);
    let channel = state.pad_channel(&page.resource_slug).await;
    let collaboration_snapshot = db::pad_collaboration_snapshot(&state.db, pad_id).await?;
    let collaborative_document = state
        .collaborative_document(
            &room_key,
            collaboration_snapshot.content,
            collaboration_snapshot.owner_map,
            collaboration_snapshot.revision_id,
        )
        .await;
    let mut document = collaborative_document.lock().await;
    let Some(next_content) =
        db::updated_public_task_content(&document.content, source_line, checked)
    else {
        return Ok(());
    };
    let base_revision_id = document.revision_id;
    let operation =
        collab::operation_from_edit(&document.content, &next_content, &document.owner_map);
    let (content, owner_map) = collab::apply_operation_to_document(
        &document.content,
        &document.owner_map,
        &operation,
        &[],
    )
    .map_err(|_| ApiError::bad_request("The task could not be updated"))?;
    let (revision_id, updated_at) =
        db::save_pad_revision(&state.db, pad_id, &content, Some("public"), &owner_map).await?;
    let update_id = u64::try_from(revision_id).unwrap_or_default().max(1);
    document.content.clone_from(&content);
    document.owner_map.clone_from(&owner_map);
    document.revision_id = revision_id;
    document.record(AppliedOperation {
        base_revision_id,
        revision_id,
        client_id: "public_task".into(),
        update_id,
        operation: operation.clone(),
        owner_replacements: Vec::new(),
    });
    let _ = channel.send(RoomEvent::Document(NoteUpdate {
        base_revision_id,
        revision_id,
        updated_at,
        author: Some("public".into()),
        client_id: "public_task".into(),
        update_id,
        operation,
        owner_replacements: Vec::new(),
    }));
    drop(document);
    Ok(())
}

async fn commit_public_note_task_update(
    state: &SharedState,
    page: &db::PublishedPage,
    source_line: usize,
    checked: bool,
) -> Result<(), ApiError> {
    let note_id = page.note_id.ok_or_else(ApiError::not_found_note)?;
    let workspace_id = page.workspace_id.ok_or_else(ApiError::not_found_note)?;
    let workspace_slug = page
        .workspace_slug
        .as_deref()
        .ok_or_else(ApiError::not_found_note)?;
    let room_key = crate::state::AppState::note_room_key(workspace_slug, &page.resource_slug);
    let channel = state
        .note_channel(workspace_slug, &page.resource_slug)
        .await;
    let collaboration_snapshot = db::note_collaboration_snapshot(&state.db, note_id).await?;
    let collaborative_document = state
        .collaborative_document(
            &room_key,
            collaboration_snapshot.content,
            collaboration_snapshot.owner_map,
            collaboration_snapshot.revision_id,
        )
        .await;
    let mut document = collaborative_document.lock().await;
    let Some(next_content) =
        db::updated_public_task_content(&document.content, source_line, checked)
    else {
        return Ok(());
    };
    let base_revision_id = document.revision_id;
    let operation =
        collab::operation_from_edit(&document.content, &next_content, &document.owner_map);
    let (content, owner_map) = collab::apply_operation_to_document(
        &document.content,
        &document.owner_map,
        &operation,
        &[],
    )
    .map_err(|_| ApiError::bad_request("The task could not be updated"))?;
    let (revision_id, updated_at) = db::save_revision(
        &state.db,
        note_id,
        workspace_id,
        &content,
        Some("public"),
        &owner_map,
    )
    .await?;
    let update_id = u64::try_from(revision_id).unwrap_or_default().max(1);
    document.content.clone_from(&content);
    document.owner_map.clone_from(&owner_map);
    document.revision_id = revision_id;
    document.record(AppliedOperation {
        base_revision_id,
        revision_id,
        client_id: "public_task".into(),
        update_id,
        operation: operation.clone(),
        owner_replacements: Vec::new(),
    });
    let _ = channel.send(RoomEvent::Document(NoteUpdate {
        base_revision_id,
        revision_id,
        updated_at,
        author: Some("public".into()),
        client_id: "public_task".into(),
        update_id,
        operation,
        owner_replacements: Vec::new(),
    }));
    drop(document);
    Ok(())
}

pub async fn update_public_task(
    State(state): State<SharedState>,
    headers: HeaderMap,
    Path(token): Path<String>,
    Json(payload): Json<PublicTaskUpdateRequest>,
) -> Result<Json<PublicPageResponse>, ApiError> {
    let current = db::find_published_page(&state.db, &token)
        .await?
        .ok_or_else(ApiError::not_found_note)?;
    ensure_public_page_access(&state, &headers, &current).await?;
    if !current.allow_task_updates {
        return Err(ApiError::forbidden(
            "Task updates are disabled for this page",
        ));
    }
    if current.pad_id.is_some() {
        commit_public_pad_task_update(&state, &current, payload.source_line, payload.checked)
            .await?;
    } else {
        commit_public_note_task_update(&state, &current, payload.source_line, payload.checked)
            .await?;
    }
    let page = db::find_published_page(&state.db, &token)
        .await?
        .ok_or_else(ApiError::not_found_note)?;
    let files =
        markdown_file_references(&state, page.pad_id, page.note_id, Some(&page.content)).await?;
    Ok(Json(PublicPageResponse {
        title: page.title,
        content: page.content,
        updated_at: db::normalize_timestamp(&page.updated_at),
        allow_task_updates: page.allow_task_updates,
        files,
    }))
}

pub async fn pad_history(
    State(state): State<SharedState>,
    headers: HeaderMap,
    Path(slug): Path<String>,
    Json(payload): Json<PasswordRequest>,
) -> Result<Json<Vec<db::Revision>>, ApiError> {
    let pad = authorized_pad(
        &state,
        &slug,
        payload.password.as_deref(),
        resource_request_token(&headers, "pad", &slug, payload.access_token.as_deref()),
        bearer_token(&headers),
        &headers,
    )
    .await?;
    let revisions = db::list_pad_revisions(&state.db, pad.id)
        .await?
        .into_iter()
        .map(|mut revision| {
            revision.created_at = db::normalize_timestamp(&revision.created_at);
            revision
        })
        .collect();
    Ok(Json(revisions))
}

pub async fn pad_restore(
    State(state): State<SharedState>,
    headers: HeaderMap,
    Path(slug): Path<String>,
    Json(payload): Json<RestoreRequest>,
) -> Result<Json<serde_json::Value>, ApiError> {
    let pad = authorized_pad(
        &state,
        &slug,
        payload.password.as_deref(),
        resource_request_token(&headers, "pad", &slug, payload.access_token.as_deref()),
        bearer_token(&headers),
        &headers,
    )
    .await?;
    let level = if db::verify_pad_password(&pad, payload.password.as_deref())
        || (pad.is_private == 0 && pad.password_hash.is_none())
    {
        AccessLevel::Write
    } else {
        request_access_level(
            &state,
            &headers,
            "pad",
            &slug,
            resource_request_token(&headers, "pad", &slug, payload.access_token.as_deref()),
            bearer_token(&headers),
        )
        .await?
    };
    require_write(level)?;
    let content: Option<String> = sqlx::query_scalar(queries::get(state.db.kind(), queries::Q029))
        .bind(payload.revision_id)
        .bind(pad.id)
        .fetch_optional(state.db.pool())
        .await?;
    let content = content.ok_or_else(ApiError::not_found_revision)?;
    let owner_map: Option<String> =
        sqlx::query_scalar(queries::get(state.db.kind(), queries::Q030))
            .bind(payload.revision_id)
            .bind(pad.id)
            .fetch_optional(state.db.pool())
            .await?;
    let owner_map = owner_map.unwrap_or_else(|| "[]".into());
    let room_key = crate::state::AppState::pad_room_key(&slug);
    let channel = state.pad_channel(&slug).await;
    let collaboration_snapshot = db::pad_collaboration_snapshot(&state.db, pad.id).await?;
    let collaborative_document = state
        .collaborative_document(
            &room_key,
            collaboration_snapshot.content,
            collaboration_snapshot.owner_map,
            collaboration_snapshot.revision_id,
        )
        .await;
    let mut document = collaborative_document.lock().await;
    let base_revision_id = document.revision_id;
    let restored_owners = collab::owner_spans_from_map(&content, &owner_map);
    let operation = collab::replace_operation(
        document.content.encode_utf16().count(),
        content,
        restored_owners,
    );
    let (content, owner_map) = collab::apply_operation_to_document(
        &document.content,
        &document.owner_map,
        &operation,
        &[],
    )
    .map_err(|_| ApiError::bad_request("The selected revision could not be restored"))?;
    let (revision_id, updated_at) =
        db::save_pad_revision(&state.db, pad.id, &content, Some("restore"), &owner_map).await?;
    let update_id = u64::try_from(revision_id).unwrap_or_default().max(1);
    let applied = AppliedOperation {
        base_revision_id,
        revision_id,
        client_id: "server_restore".into(),
        update_id,
        operation: operation.clone(),
        owner_replacements: Vec::new(),
    };
    document.content.clone_from(&content);
    document.owner_map.clone_from(&owner_map);
    document.revision_id = revision_id;
    document.record(applied);
    let update = NoteUpdate {
        base_revision_id,
        revision_id,
        updated_at,
        author: Some("restore".into()),
        client_id: "server_restore".into(),
        update_id,
        operation,
        owner_replacements: Vec::new(),
    };
    let _ = channel.send(RoomEvent::Document(update));
    drop(document);
    Ok(Json(serde_json::json!({"ok": true})))
}

pub(super) async fn authorized_pad(
    state: &SharedState,
    slug: &str,
    password: Option<&str>,
    access_token: Option<&str>,
    bearer: Option<&str>,
    headers: &HeaderMap,
) -> Result<db::Pad, ApiError> {
    let pad = db::find_pad(&state.db, slug)
        .await?
        .ok_or_else(ApiError::not_found_note)?;
    let token_level =
        request_access_level(state, headers, "pad", slug, access_token, bearer).await?;
    if pad.is_private != 0 && token_level == AccessLevel::None {
        return Err(ApiError::not_found_note());
    }
    if pad.password_hash.is_some() && token_level < AccessLevel::Write {
        let password_ok = db::verify_pad_password(&pad, password);
        check_resource_password_attempt(state, headers, "pad", slug, password, password_ok).await?;
        if token_level == AccessLevel::None && !password_ok {
            return Err(ApiError::forbidden("Password required or incorrect."));
        }
    }
    Ok(pad)
}

async fn unique_pad_slug(state: &SharedState, base: &str) -> Result<String, ApiError> {
    if db::find_pad(&state.db, base).await?.is_none() {
        return Ok(base.to_owned());
    }
    for _ in 0..8 {
        let candidate = format!("{base}-{}", db::random_suffix(6));
        if db::find_pad(&state.db, &candidate).await?.is_none() {
            return Ok(candidate);
        }
    }
    Err(ApiError::internal("Failed to create a unique address"))
}