#![allow(missing_docs)]

#[cfg(engine)]
use crate::i18n::TranslationsManagerError;
use thiserror::Error;

/// All errors that can be returned from this crate.
#[derive(Error, Debug)]
pub enum Error {
    #[error(transparent)]
    ClientError(#[from] ClientError),
    #[cfg(engine)]
    #[error(transparent)]
    ServerError(#[from] ServerError),
    #[cfg(engine)]
    #[error(transparent)]
    EngineError(#[from] EngineError),
    // Plugin errors could come from literally anywhere, and could have entirely arbitrary data
    #[error(transparent)]
    PluginError(#[from] PluginError),
}

#[derive(Error, Debug)]
#[error("plugin '{name}' returned an error (this is unlikely to be Perseus' fault)")]
pub struct PluginError {
    pub name: String,
    #[source]
    pub source: Box<dyn std::error::Error + Send + Sync>,
}

/// Errors that can occur in the server-side engine system (responsible for
/// building the app).
#[cfg(engine)]
#[derive(Error, Debug)]
pub enum EngineError {
    // Many of the build/export processes return these more generic errors
    #[error(transparent)]
    ServerError(#[from] ServerError),
    #[error("couldn't copy static directory at '{path}' to '{dest}'")]
    CopyStaticDirError {
        #[source]
        source: fs_extra::error::Error,
        path: String,
        dest: String,
    },
    #[error("couldn't copy static alias file from '{from}' to '{to}'")]
    CopyStaticAliasFileError {
        #[source]
        source: std::io::Error,
        from: String,
        to: String,
    },
    #[error("couldn't copy static alias directory from '{from}' to '{to}'")]
    CopyStaticAliasDirErr {
        #[source]
        source: fs_extra::error::Error,
        from: String,
        to: String,
    },
    #[error("couldn't write the generated error page to '{dest}'")]
    WriteErrorPageError {
        #[source]
        source: std::io::Error,
        dest: String,
    },
    #[error("couldn't create the parent directories needed for the nested static alias '{alias}'")]
    NestedStaticAliasDirCreationFailed {
        #[source]
        source: std::io::Error,
        alias: String,
    },
}

/// Errors that can occur in the browser.
///
/// **Important:** any changes to this `enum` constitute a breaking change,
/// since users match this in their error pages. Changes in underlying
/// `enum`s are not considered breaking (e.g. introducing a new invariant
/// error).
///
/// **Warning:** in all these cases, except `ClientError::ServerError`, the user
/// can already see the prerendered version of the page, it just isn't
/// interactive. Only in that case will your error page occupy the entire
/// screen, otherwise it will be placed into a `div` with the class
/// `__perseus-error`, a deliberate choice to reinforce the best practice of
/// giving the user as much as possible (it might not be interactive, but they
/// can still use a rudimentary version). See the book for further details.
///
/// # Panic handling
/// In a rather unorthodox manner, Perseus will do its level best to get an
/// error message to the user of your app, no matter what happens. For this
/// reason, this `enum` includes a `Panic` variant that will be provided when a
/// panic has been intercepted. In this case, your error view will be rendered
/// with no reactor, translations, or anything else available to it. What you do
/// at this time is extremely important, since any panics in the code that
/// handles that variant **cannot be caught**, leaving the user with no error
/// message and an app that has completely frozen.
///
/// The `Panic` variant on this type only provides a formatted panic message,
/// and nothing else from [`std::panic::PanicInfo`], due to lifetime
/// constraints. Since the message formatting is done by the standard library,
/// which automatically takes account of the `payload` and `message`, the only
/// other properties are `location` and `can_unwind`: the latter should be
/// handled by Perseus if it ever is, and the former shoudl not be exposed to
/// end users. Currently, there is no way to get the underlying `PanicInfo`
/// through Perseus' error handling system (although a plugin could do it
/// by overriding the panic handler, but this is usually a bad idea).
#[derive(Error, Debug)]
pub enum ClientError {
    #[error("{0}")] // All formatted for us by `std`
    Panic(String),
    #[error(transparent)]
    PluginError(#[from] PluginError),
    #[error(transparent)]
    InvariantError(#[from] ClientInvariantError),
    #[error(transparent)]
    ThawError(#[from] ClientThawError),
    // Not like the `ServerError` in this file!
    #[error("an error with HTTP status code '{status}' was returned by the server: '{message}'")]
    ServerError {
        status: u16,
        // This has to have been serialized unfortunately
        message: String,
    },
    #[error(transparent)]
    FetchError(#[from] FetchError),
    #[error(transparent)]
    PlatformError(#[from] ClientPlatformError),
    #[error(transparent)]
    PreloadError(#[from] ClientPreloadError), /* #[error(transparent)]
                                               * FetchError(#[from] FetchError),
                                               * ,
                                               * // If the user is using the template macros, this should never be emitted because we can
                                               * // ensure that the generated state is valid
                                               * #[error("tried to deserialize invalid state
                                               * (it was not malformed, but the state was not
                                               * of
                                               * the declared type)")] StateInvalid {
                                               *     #[source]
                                               *     source: serde_json::Error,
                                               * },
                                               * #[error("server informed us that a valid
                                               * locale was invald (this almost certainly
                                               * requires
                                               * a hard reload)")] ValidLocaleNotProvided {
                                               * locale: String },
                                               */
}

/// Errors that can occur in the browser from certain invariants not being
/// upheld. These should be extremely rare, but, since we don't control what
/// HTML the browser gets, we avoid panicking in these cases.
///
/// Note that some of these invariants may be broken by an app's own code, such
/// as invalid global state downcasting.
#[derive(Debug, Error)]
pub enum ClientInvariantError {
    #[error("the render configuration was not found, or was malformed")]
    RenderCfg,
    #[error("the global state was not found, or was malformed (even apps not using global state should have an empty one injected)")]
    GlobalState,
    // This won't be triggered for HSR
    #[error("attempted to register state on a page/capsule that had been previously declared as having no state")]
    IllegalStateRegistration,
    #[error(
        "attempted to downcast reactive global state to the incorrect type (this is an error)"
    )]
    GlobalStateDowncast,
    // This is technically a typing error, but we do the typing internally, so this should be
    // impossible
    #[error("invalid page/widget state found")]
    InvalidState {
        #[source]
        source: serde_json::Error,
    },
    // Invariant because the user would have had to call something like `.template_with_state()`
    // for this to happen
    #[error("no state was found for a page/widget that expected state (you might have forgotten to write a state generation function, like `get_build_state`)")]
    NoState,
    #[error("the initial state was not found, or was malformed")]
    InitialState,
    #[error("the initial state denoted an error, but this was malformed")]
    InitialStateError {
        #[source]
        source: serde_json::Error,
    },
    #[error(
        "the locale '{locale}', which is supported by this app, was not returned by the server"
    )]
    ValidLocaleNotProvided { locale: String },
    // This is just for initial loads (`__PERSEUS_TRANSLATIONS` window variable)
    #[error("the translations were not found, or were malformed (even apps not using i18n have a declaration of their lack of translations)")]
    Translations,
    #[error("we found the current page to be a 404, but the engine disagrees")]
    RouterMismatch,
    #[error("the widget states were not found, or were malformed (even pages not using widgets still have a declaration of these)")]
    WidgetStates,
    #[error("a widget was registered in the state store with only a head (but widgets do not have heads), implying a corruption")]
    InvalidWidgetPssEntry,
    #[error("the widget with path '{path}' was not found, indicating you are rendering an invalid widget on the browser-side only (you should refactor to always render the widget, but only have it do anything on the browser-side; that way, it can be verified on the engine-side, leading to errors at build-time rather than execution-time)")]
    BadWidgetRouteMatch { path: String },
}

/// Errors that can occur as a result of user-instructed preloads. Note that
/// this will not cover network-related errors, which are considered fetch
/// errors (since they are likely not the fault of your code, whereas a
/// `ClientPreloadError` probably is).
#[derive(Debug, Error)]
pub enum ClientPreloadError {
    #[error("preloading '{path}' leads to a locale detection page, which implies a malformed url")]
    PreloadLocaleDetection { path: String },
    #[error("'{path}' was not found for preload")]
    PreloadNotFound { path: String },
}

/// Errors that can occur in the browser while interfacing with browser
/// functionality. These should never really occur unless you're operating in an
/// extremely alien environment (which probably wouldn't support Wasm, but
/// we try to allow maximal error page control).
#[derive(Debug, Error)]
pub enum ClientPlatformError {
    #[error("failed to get current url for initial load determination")]
    InitialPath,
}

/// Errors that can occur in the browser as a result of attempting to thaw
/// provided state.
#[derive(Debug, Error)]
pub enum ClientThawError {
    #[error("invalid frozen page/widget state")]
    InvalidFrozenState {
        #[source]
        source: serde_json::Error,
    },
    #[error("invalid frozen global state")]
    InvalidFrozenGlobalState {
        #[source]
        source: serde_json::Error,
    },
    #[error("this app uses global state, but the provided frozen state declared itself to have no global state")]
    NoFrozenGlobalState,
    #[error("invalid frozen app provided (this is likely a corruption)")]
    InvalidFrozenApp {
        #[source]
        source: serde_json::Error,
    },
}

/// Errors that can occur in the build process or while the server is running.
#[cfg(engine)]
#[derive(Error, Debug)]
pub enum ServerError {
    #[error("render function '{fn_name}' in template '{template_name}' failed (cause: {blame:?})")]
    RenderFnFailed {
        // This is something like `build_state`
        fn_name: String,
        template_name: String,
        blame: ErrorBlame,
        // This will be triggered by the user's custom render functions, which should be able to
        // have any error type
        #[source]
        source: Box<dyn std::error::Error + Send + Sync>,
    },
    // We should only get a failure to minify if the user has given invalid HTML, or if Sycamore
    // stuffed up somewhere
    #[error("failed to minify html (you can disable the `minify` flag to avoid this; this is very likely a Sycamore bug, unless you've provided invalid custom HTML)")]
    MinifyError {
        #[source]
        source: std::io::Error,
    },
    #[error("failed to decode url provided (probably malformed request)")]
    UrlDecodeFailed {
        #[source]
        source: std::string::FromUtf8Error,
    },
    #[error("the template '{template_name}' had no helper build state written to the immutable store (the store has been tampered with, and the app must be rebuilt)")]
    MissingBuildExtra { template_name: String },
    #[error("the template '{template_name}' had invalid helper build state written to the immutable store (the store has been tampered with, and the app must be rebuilt)")]
    InvalidBuildExtra {
        template_name: String,
        #[source]
        source: serde_json::Error,
    },
    #[error("page state was encountered that could not be deserialized into serde_json::Value (the store has been tampered with, and the app must be rebuilt)")]
    InvalidPageState {
        #[source]
        source: serde_json::Error,
    },

    // `PathWithoutLocale`
    #[error("attempting to resolve dependency '{widget}' in locale '{locale}' produced a locale redirection verdict (this shouldn't be possible)")]
    ResolveDepLocaleRedirection { widget: String, locale: String },
    #[error("attempting to resolve dependency '{widget}' in locale '{locale}' produced a not found verdict (did you mistype the widget path?)")]
    ResolveDepNotFound { widget: String, locale: String },

    #[error("template '{template_name}' cannot be built at build-time due to one or more of its dependencies having state that may change later; to allow this template to be built later, add `.allow_rescheduling()` to your template definition")]
    TemplateCannotBeRescheduled { template_name: String },
    // This is a serious error in programming
    #[error("a dependency tree was not resolved, but a function expecting it to have been was called (this is a server-side error)")]
    DepTreeNotResolved,
    #[error("the template name did not prefix the path (this request was severely malformed)")]
    TemplateNameNotInPath,

    #[error(transparent)]
    StoreError(#[from] StoreError),
    #[error(transparent)]
    TranslationsManagerError(#[from] TranslationsManagerError),
    #[error(transparent)]
    BuildError(#[from] BuildError),
    #[error(transparent)]
    ExportError(#[from] ExportError),
    #[error(transparent)]
    ServeError(#[from] ServeError),
    #[error(transparent)]
    PluginError(#[from] PluginError),
    // This can occur in state acquisition failures during prerendering
    #[error(transparent)]
    ClientError(#[from] ClientError),
}
/// Converts a server error into an HTTP status code.
#[cfg(engine)]
pub fn err_to_status_code(err: &ServerError) -> u16 {
    match err {
        ServerError::ServeError(ServeError::PageNotFound { .. }) => 404,
        // Ambiguous (user-generated error), we'll rely on the given cause
        ServerError::RenderFnFailed { blame, .. } => match blame {
            ErrorBlame::Client(code) => code.unwrap_or(400),
            ErrorBlame::Server(code) => code.unwrap_or(500),
        },
        // Any other errors go to a 500, they'll be misconfigurations or internal server errors
        _ => 500,
    }
}

/// Errors that can occur while reading from or writing to a mutable or
/// immutable store.
// We do need this on the client to complete some things
#[derive(Error, Debug)]
pub enum StoreError {
    #[error("asset '{name}' not found in store")]
    NotFound { name: String },
    #[error("asset '{name}' couldn't be read from store")]
    ReadFailed {
        name: String,
        #[source]
        source: Box<dyn std::error::Error + Send + Sync>,
    },
    #[error("asset '{name}' couldn't be written to store")]
    WriteFailed {
        name: String,
        #[source]
        source: Box<dyn std::error::Error + Send + Sync>,
    },
}

/// Errors that can occur while fetching a resource from the server.
#[derive(Error, Debug)]
pub enum FetchError {
    #[error("asset of type '{ty}' fetched from '{url}' wasn't a string")]
    NotString { url: String, ty: AssetType },
    #[error(
        "asset of type '{ty}' fetched from '{url}' returned status code '{status}' (expected 200)"
    )]
    NotOk {
        url: String,
        status: u16,
        // The underlying body of the HTTP error response
        err: String,
        ty: AssetType,
    },
    #[error("asset of type '{ty}' fetched from '{url}' couldn't be serialized")]
    SerFailed {
        url: String,
        #[source]
        source: Box<dyn std::error::Error + Send + Sync>,
        ty: AssetType,
    },
    /// This converts from a `JsValue` or the like.
    #[error("the following error occurred while interfacing with JavaScript: {0}")]
    Js(String),
}

/// The type of an asset fetched from the server. This allows distinguishing
/// between errors in fetching, say, pages, vs. translations, which you may wish
/// to handle differently.
#[derive(Debug, Clone, Copy)]
pub enum AssetType {
    /// A page in the app.
    Page,
    /// A widget in the app.
    Widget,
    /// Translations for a locale.
    Translations,
    /// A page/widget the user asked to have preloaded.
    Preload,
}
impl std::fmt::Display for AssetType {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        write!(f, "{:?}", self)
    }
}

/// Errors that can occur while building an app.
#[cfg(engine)]
#[derive(Error, Debug)]
pub enum BuildError {
    #[error("template '{template_name}' is missing feature '{feature_name}' (required due to its properties)")]
    TemplateFeatureNotEnabled {
        template_name: String,
        feature_name: String,
    },
    #[error("html shell couldn't be found at '{path}'")]
    HtmlShellNotFound {
        path: String,
        #[source]
        source: std::io::Error,
    },
    #[error(
        "invalid indicator '{indicator}' in time string (must be one of: s, m, h, d, w, M, y)"
    )]
    InvalidDatetimeIntervalIndicator { indicator: String },
    #[error("asset 'render_cfg.json' invalid or corrupted (try cleaning all assets)")]
    RenderCfgInvalid {
        #[source]
        source: serde_json::Error,
    },
}

/// Errors that can occur while exporting an app to static files.
#[cfg(engine)]
#[derive(Error, Debug)]
pub enum ExportError {
    #[error("template '{template_name}' can't be exported because it depends on strategies that can't be run at build-time (only build state and build paths can be used in exportable templates)")]
    TemplateNotExportable { template_name: String },
    #[error("template '{template_name}' wasn't found in built artifacts (run `perseus clean --dist` if this persists)")]
    TemplateNotFound { template_name: String },
    #[error("your app can't be exported because its global state depends on strategies that can't be run at build time (only build state can be used in exportable apps)")]
    GlobalStateNotExportable,
    #[error("template '{template_name} can't be exported because one or more of its widget dependencies use state generation strategies that can't be run at build-time")]
    DependenciesNotExportable { template_name: String },
    // This is used in error page exports
    #[error("invalid status code provided for error page export (please provide a valid http status code)")]
    InvalidStatusCode,
}

/// Errors that can occur while serving an app. These are integration-agnostic.
#[derive(Error, Debug)]
pub enum ServeError {
    #[error("page/widget at '{path}' not found")]
    PageNotFound { path: String },
    #[error("both build and request states were defined for a template when only one or fewer were expected (should it be able to amalgamate states?)")]
    BothStatesDefined,
    #[cfg(engine)]
    #[error("couldn't parse revalidation datetime (try cleaning all assets)")]
    BadRevalidate {
        #[source]
        source: chrono::ParseError,
    },
}

/// Defines who caused an ambiguous error message so we can reliably create an
/// HTTP status code. Specific status codes may be provided in either case, or
/// the defaults (400 for client, 500 for server) will be used.
///
/// The default implementation will produce a server-blamed 500 error.
#[derive(Debug)]
pub enum ErrorBlame {
    Client(Option<u16>),
    Server(Option<u16>),
}
impl Default for ErrorBlame {
    fn default() -> Self {
        Self::Server(None)
    }
}

/// An error that has an attached cause that blames either the client or the
/// server for its occurrence. You can convert any error into this with
/// `.into()` or `?`, which will set the cause to the server by default,
/// resulting in a *500 Internal Server Error* HTTP status code. If this isn't
/// what you want, you'll need to initialize this explicitly.
///
/// *Note for those using `anyhow`: use `.map_err(|e| anyhow::anyhow!(e))?`
/// to use anyhow in Perseus render functions.*
#[cfg(engine)]
#[derive(Debug)]
pub struct BlamedError<E: Send + Sync> {
    /// The underlying error.
    pub error: E,
    /// Who is to blame for the error.
    pub blame: ErrorBlame,
}
#[cfg(engine)]
impl<E: Into<Box<dyn std::error::Error + Send + Sync + 'static>> + Send + Sync> BlamedError<E> {
    /// Converts this blamed error into an internal boxed version that is
    /// generic over the error type.
    pub(crate) fn into_boxed(self) -> GenericBlamedError {
        BlamedError {
            error: self.error.into(),
            blame: self.blame,
        }
    }
}
// We should be able to convert any error into this easily (e.g. with `?`) with
// the default being to blame the server
#[cfg(engine)]
impl<E: Into<Box<dyn std::error::Error + Send + Sync + 'static>> + Send + Sync> From<E>
    for BlamedError<E>
{
    fn from(error: E) -> Self {
        Self {
            error,
            blame: ErrorBlame::default(),
        }
    }
}

/// A simple wrapper for generic, boxed, blamed errors.
#[cfg(engine)]
pub(crate) type GenericBlamedError = BlamedError<Box<dyn std::error::Error + Send + Sync>>;