// Copyright 2022-2024 The Jujutsu Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use std::error;
use std::io;
use std::io::Write as _;
use std::iter;
use std::process::ExitCode;
use std::str;
use std::sync::Arc;

use itertools::Itertools as _;
use jj_lib::absorb::AbsorbError;
use jj_lib::backend::BackendError;
use jj_lib::config::ConfigFileSaveError;
use jj_lib::config::ConfigGetError;
use jj_lib::config::ConfigLoadError;
use jj_lib::config::ConfigMigrateError;
use jj_lib::dsl_util::Diagnostics;
use jj_lib::fileset::FilePatternParseError;
use jj_lib::fileset::FilesetParseError;
use jj_lib::fileset::FilesetParseErrorKind;
use jj_lib::gitignore::GitIgnoreError;
use jj_lib::op_heads_store::OpHeadResolutionError;
use jj_lib::op_heads_store::OpHeadsStoreError;
use jj_lib::op_store::OpStoreError;
use jj_lib::op_walk::OpsetEvaluationError;
use jj_lib::op_walk::OpsetResolutionError;
use jj_lib::repo::CheckOutCommitError;
use jj_lib::repo::EditCommitError;
use jj_lib::repo::RepoLoaderError;
use jj_lib::repo::RewriteRootCommit;
use jj_lib::repo_path::RepoPathBuf;
use jj_lib::repo_path::UiPathParseError;
use jj_lib::revset::RevsetEvaluationError;
use jj_lib::revset::RevsetParseError;
use jj_lib::revset::RevsetParseErrorKind;
use jj_lib::revset::RevsetResolutionError;
use jj_lib::str_util::StringPatternParseError;
use jj_lib::view::RenameWorkspaceError;
use jj_lib::working_copy::RecoverWorkspaceError;
use jj_lib::working_copy::ResetError;
use jj_lib::working_copy::SnapshotError;
use jj_lib::working_copy::WorkingCopyStateError;
use jj_lib::workspace::WorkspaceInitError;
use thiserror::Error;

use crate::cli_util::short_operation_hash;
use crate::config::ConfigEnvError;
use crate::description_util::ParseBulkEditMessageError;
use crate::description_util::TempTextEditError;
use crate::description_util::TextEditError;
use crate::diff_util::DiffRenderError;
use crate::formatter::FormatRecorder;
use crate::formatter::Formatter;
use crate::merge_tools::ConflictResolveError;
use crate::merge_tools::DiffEditError;
use crate::merge_tools::MergeToolConfigError;
use crate::merge_tools::MergeToolPartialResolutionError;
use crate::revset_util::UserRevsetEvaluationError;
use crate::template_parser::TemplateParseError;
use crate::template_parser::TemplateParseErrorKind;
use crate::ui::Ui;

#[derive(Clone, Copy, Debug, Eq, PartialEq)]
pub enum CommandErrorKind {
    User,
    Config,
    /// Invalid command line. The inner error type may be `clap::Error`.
    Cli,
    BrokenPipe,
    Internal,
}

#[derive(Clone, Debug)]
pub struct CommandError {
    pub kind: CommandErrorKind,
    pub error: Arc<dyn error::Error + Send + Sync>,
    pub hints: Vec<ErrorHint>,
}

impl CommandError {
    pub fn new(
        kind: CommandErrorKind,
        err: impl Into<Box<dyn error::Error + Send + Sync>>,
    ) -> Self {
        CommandError {
            kind,
            error: Arc::from(err.into()),
            hints: vec![],
        }
    }

    pub fn with_message(
        kind: CommandErrorKind,
        message: impl Into<String>,
        source: impl Into<Box<dyn error::Error + Send + Sync>>,
    ) -> Self {
        Self::new(kind, ErrorWithMessage::new(message, source))
    }

    /// Returns error with the given plain-text `hint` attached.
    pub fn hinted(mut self, hint: impl Into<String>) -> Self {
        self.add_hint(hint);
        self
    }

    /// Appends plain-text `hint` to the error.
    pub fn add_hint(&mut self, hint: impl Into<String>) {
        self.hints.push(ErrorHint::PlainText(hint.into()));
    }

    /// Appends formatted `hint` to the error.
    pub fn add_formatted_hint(&mut self, hint: FormatRecorder) {
        self.hints.push(ErrorHint::Formatted(hint));
    }

    /// Constructs formatted hint and appends it to the error.
    pub fn add_formatted_hint_with(
        &mut self,
        write: impl FnOnce(&mut dyn Formatter) -> io::Result<()>,
    ) {
        let mut formatter = FormatRecorder::new();
        write(&mut formatter).expect("write() to FormatRecorder should never fail");
        self.add_formatted_hint(formatter);
    }

    /// Appends 0 or more plain-text `hints` to the error.
    pub fn extend_hints(&mut self, hints: impl IntoIterator<Item = String>) {
        self.hints
            .extend(hints.into_iter().map(ErrorHint::PlainText));
    }
}

#[derive(Clone, Debug)]
pub enum ErrorHint {
    PlainText(String),
    Formatted(FormatRecorder),
}

/// Wraps error with user-visible message.
#[derive(Debug, Error)]
#[error("{message}")]
struct ErrorWithMessage {
    message: String,
    source: Box<dyn error::Error + Send + Sync>,
}

impl ErrorWithMessage {
    fn new(
        message: impl Into<String>,
        source: impl Into<Box<dyn error::Error + Send + Sync>>,
    ) -> Self {
        ErrorWithMessage {
            message: message.into(),
            source: source.into(),
        }
    }
}

pub fn user_error(err: impl Into<Box<dyn error::Error + Send + Sync>>) -> CommandError {
    CommandError::new(CommandErrorKind::User, err)
}

pub fn user_error_with_hint(
    err: impl Into<Box<dyn error::Error + Send + Sync>>,
    hint: impl Into<String>,
) -> CommandError {
    user_error(err).hinted(hint)
}

pub fn user_error_with_message(
    message: impl Into<String>,
    source: impl Into<Box<dyn error::Error + Send + Sync>>,
) -> CommandError {
    CommandError::with_message(CommandErrorKind::User, message, source)
}

pub fn config_error(err: impl Into<Box<dyn error::Error + Send + Sync>>) -> CommandError {
    CommandError::new(CommandErrorKind::Config, err)
}

pub fn config_error_with_message(
    message: impl Into<String>,
    source: impl Into<Box<dyn error::Error + Send + Sync>>,
) -> CommandError {
    CommandError::with_message(CommandErrorKind::Config, message, source)
}

pub fn cli_error(err: impl Into<Box<dyn error::Error + Send + Sync>>) -> CommandError {
    CommandError::new(CommandErrorKind::Cli, err)
}

pub fn internal_error(err: impl Into<Box<dyn error::Error + Send + Sync>>) -> CommandError {
    CommandError::new(CommandErrorKind::Internal, err)
}

pub fn internal_error_with_message(
    message: impl Into<String>,
    source: impl Into<Box<dyn error::Error + Send + Sync>>,
) -> CommandError {
    CommandError::with_message(CommandErrorKind::Internal, message, source)
}

fn format_similarity_hint<S: AsRef<str>>(candidates: &[S]) -> Option<String> {
    match candidates {
        [] => None,
        names => {
            let quoted_names = names.iter().map(|s| format!("`{}`", s.as_ref())).join(", ");
            Some(format!("Did you mean {quoted_names}?"))
        }
    }
}

impl From<io::Error> for CommandError {
    fn from(err: io::Error) -> Self {
        let kind = match err.kind() {
            io::ErrorKind::BrokenPipe => CommandErrorKind::BrokenPipe,
            _ => CommandErrorKind::User,
        };
        CommandError::new(kind, err)
    }
}

impl From<jj_lib::file_util::PathError> for CommandError {
    fn from(err: jj_lib::file_util::PathError) -> Self {
        user_error(err)
    }
}

impl From<ConfigEnvError> for CommandError {
    fn from(err: ConfigEnvError) -> Self {
        config_error(err)
    }
}

impl From<ConfigFileSaveError> for CommandError {
    fn from(err: ConfigFileSaveError) -> Self {
        user_error(err)
    }
}

impl From<ConfigGetError> for CommandError {
    fn from(err: ConfigGetError) -> Self {
        let hint = config_get_error_hint(&err);
        let mut cmd_err = config_error(err);
        cmd_err.extend_hints(hint);
        cmd_err
    }
}

impl From<ConfigLoadError> for CommandError {
    fn from(err: ConfigLoadError) -> Self {
        let hint = match &err {
            ConfigLoadError::Read(_) => None,
            ConfigLoadError::Parse { source_path, .. } => source_path
                .as_ref()
                .map(|path| format!("Check the config file: {}", path.display())),
        };
        let mut cmd_err = config_error(err);
        cmd_err.extend_hints(hint);
        cmd_err
    }
}

impl From<ConfigMigrateError> for CommandError {
    fn from(err: ConfigMigrateError) -> Self {
        let hint = err
            .source_path
            .as_ref()
            .map(|path| format!("Check the config file: {}", path.display()));
        let mut cmd_err = config_error(err);
        cmd_err.extend_hints(hint);
        cmd_err
    }
}

impl From<RewriteRootCommit> for CommandError {
    fn from(err: RewriteRootCommit) -> Self {
        internal_error_with_message("Attempted to rewrite the root commit", err)
    }
}

impl From<EditCommitError> for CommandError {
    fn from(err: EditCommitError) -> Self {
        internal_error_with_message("Failed to edit a commit", err)
    }
}

impl From<CheckOutCommitError> for CommandError {
    fn from(err: CheckOutCommitError) -> Self {
        internal_error_with_message("Failed to check out a commit", err)
    }
}

impl From<RenameWorkspaceError> for CommandError {
    fn from(err: RenameWorkspaceError) -> Self {
        user_error_with_message("Failed to rename a workspace", err)
    }
}

impl From<BackendError> for CommandError {
    fn from(err: BackendError) -> Self {
        match &err {
            BackendError::Unsupported(_) => user_error(err),
            _ => internal_error_with_message("Unexpected error from backend", err),
        }
    }
}

impl From<OpHeadsStoreError> for CommandError {
    fn from(err: OpHeadsStoreError) -> Self {
        internal_error_with_message("Unexpected error from operation heads store", err)
    }
}

impl From<WorkspaceInitError> for CommandError {
    fn from(err: WorkspaceInitError) -> Self {
        match err {
            WorkspaceInitError::DestinationExists(_) => {
                user_error("The target repo already exists")
            }
            WorkspaceInitError::NonUnicodePath => {
                user_error("The target repo path contains non-unicode characters")
            }
            WorkspaceInitError::CheckOutCommit(err) => {
                internal_error_with_message("Failed to check out the initial commit", err)
            }
            WorkspaceInitError::Path(err) => {
                internal_error_with_message("Failed to access the repository", err)
            }
            WorkspaceInitError::OpHeadsStore(err) => {
                user_error_with_message("Failed to record initial operation", err)
            }
            WorkspaceInitError::Backend(err) => {
                user_error_with_message("Failed to access the repository", err)
            }
            WorkspaceInitError::WorkingCopyState(err) => {
                internal_error_with_message("Failed to access the repository", err)
            }
            WorkspaceInitError::SignInit(err) => user_error(err),
        }
    }
}

impl From<OpHeadResolutionError> for CommandError {
    fn from(err: OpHeadResolutionError) -> Self {
        match err {
            OpHeadResolutionError::NoHeads => {
                internal_error_with_message("Corrupt repository", err)
            }
        }
    }
}

impl From<OpsetEvaluationError> for CommandError {
    fn from(err: OpsetEvaluationError) -> Self {
        match err {
            OpsetEvaluationError::OpsetResolution(err) => {
                let hint = opset_resolution_error_hint(&err);
                let mut cmd_err = user_error(err);
                cmd_err.extend_hints(hint);
                cmd_err
            }
            OpsetEvaluationError::OpHeadResolution(err) => err.into(),
            OpsetEvaluationError::OpHeadsStore(err) => err.into(),
            OpsetEvaluationError::OpStore(err) => err.into(),
        }
    }
}

impl From<SnapshotError> for CommandError {
    fn from(err: SnapshotError) -> Self {
        internal_error_with_message("Failed to snapshot the working copy", err)
    }
}

impl From<OpStoreError> for CommandError {
    fn from(err: OpStoreError) -> Self {
        internal_error_with_message("Failed to load an operation", err)
    }
}

impl From<RepoLoaderError> for CommandError {
    fn from(err: RepoLoaderError) -> Self {
        internal_error_with_message("Failed to load the repo", err)
    }
}

impl From<ResetError> for CommandError {
    fn from(err: ResetError) -> Self {
        internal_error_with_message("Failed to reset the working copy", err)
    }
}

impl From<DiffEditError> for CommandError {
    fn from(err: DiffEditError) -> Self {
        user_error_with_message("Failed to edit diff", err)
    }
}

impl From<DiffRenderError> for CommandError {
    fn from(err: DiffRenderError) -> Self {
        match err {
            DiffRenderError::DiffGenerate(_) => user_error(err),
            DiffRenderError::Backend(err) => err.into(),
            DiffRenderError::AccessDenied { .. } => user_error(err),
            DiffRenderError::InvalidRepoPath(_) => user_error(err),
            DiffRenderError::Io(err) => err.into(),
        }
    }
}

impl From<ConflictResolveError> for CommandError {
    fn from(err: ConflictResolveError) -> Self {
        match err {
            ConflictResolveError::Backend(err) => err.into(),
            ConflictResolveError::Io(err) => err.into(),
            _ => user_error_with_message("Failed to resolve conflicts", err),
        }
    }
}

impl From<MergeToolPartialResolutionError> for CommandError {
    fn from(err: MergeToolPartialResolutionError) -> Self {
        user_error(err)
    }
}

impl From<MergeToolConfigError> for CommandError {
    fn from(err: MergeToolConfigError) -> Self {
        match &err {
            MergeToolConfigError::MergeArgsNotConfigured { tool_name } => {
                let tool_name = tool_name.clone();
                user_error_with_hint(
                    err,
                    format!(
                        "To use `{tool_name}` as a merge tool, the config \
                         `merge-tools.{tool_name}.merge-args` must be defined (see docs for \
                         details)"
                    ),
                )
            }
            _ => user_error_with_message("Failed to load tool configuration", err),
        }
    }
}

impl From<TextEditError> for CommandError {
    fn from(err: TextEditError) -> Self {
        user_error(err)
    }
}

impl From<TempTextEditError> for CommandError {
    fn from(err: TempTextEditError) -> Self {
        let hint = err.path.as_ref().map(|path| {
            let name = err.name.as_deref().unwrap_or("file");
            format!("Edited {name} is left in {path}", path = path.display())
        });
        let mut cmd_err = user_error(err);
        cmd_err.extend_hints(hint);
        cmd_err
    }
}

#[cfg(feature = "git")]
mod git {
    use jj_lib::git::GitConfigParseError;
    use jj_lib::git::GitExportError;
    use jj_lib::git::GitFetchError;
    use jj_lib::git::GitFetchPrepareError;
    use jj_lib::git::GitImportError;
    use jj_lib::git::GitPushError;
    use jj_lib::git::GitRemoteManagementError;
    use jj_lib::git::UnexpectedGitBackendError;

    use super::*;

    impl From<git2::Error> for CommandError {
        fn from(err: git2::Error) -> Self {
            user_error_with_message("Git operation failed", err)
        }
    }

    impl From<GitImportError> for CommandError {
        fn from(err: GitImportError) -> Self {
            let hint = match &err {
                GitImportError::MissingHeadTarget { .. }
                | GitImportError::MissingRefAncestor { .. } => Some(
                    "\
Is this Git repository a partial clone (cloned with the --filter argument)?
jj currently does not support partial clones. To use jj with this repository, try re-cloning with \
                     the full repository contents."
                        .to_string(),
                ),
                GitImportError::RemoteReservedForLocalGitRepo => {
                    Some("Run `jj git remote rename` to give different name.".to_string())
                }
                GitImportError::InternalBackend(_) => None,
                GitImportError::InternalGitError(_) => None,
                GitImportError::UnexpectedBackend(_) => None,
            };
            let mut cmd_err =
                user_error_with_message("Failed to import refs from underlying Git repo", err);
            cmd_err.extend_hints(hint);
            cmd_err
        }
    }

    impl From<GitExportError> for CommandError {
        fn from(err: GitExportError) -> Self {
            internal_error_with_message("Failed to export refs to underlying Git repo", err)
        }
    }

    impl From<GitFetchError> for CommandError {
        fn from(err: GitFetchError) -> Self {
            if let GitFetchError::InvalidBranchPattern(pattern) = &err {
                if pattern.as_exact().is_some_and(|s| s.contains('*')) {
                    return user_error_with_hint(
                        "Branch names may not include `*`.",
                        "Prefix the pattern with `glob:` to expand `*` as a glob",
                    );
                }
            }
            match err {
                GitFetchError::NoSuchRemote(_) => user_error(err),
                GitFetchError::InvalidBranchPattern(_) => user_error(err),
                GitFetchError::InternalGitError(err) => map_git2_error(err),
                GitFetchError::Subprocess(_) => user_error(err),
            }
        }
    }

    impl From<GitFetchPrepareError> for CommandError {
        fn from(err: GitFetchPrepareError) -> Self {
            match err {
                GitFetchPrepareError::Git2(err) => map_git2_error(err),
                GitFetchPrepareError::UnexpectedBackend(_) => user_error(err),
            }
        }
    }

    impl From<GitPushError> for CommandError {
        fn from(err: GitPushError) -> Self {
            match err {
                GitPushError::NoSuchRemote(_) => user_error(err),
                GitPushError::RemoteReservedForLocalGitRepo => user_error(err),
                GitPushError::RefInUnexpectedLocation(refs) => user_error_with_hint(
                    format!(
                        "Refusing to push a bookmark that unexpectedly moved on the remote. \
                         Affected refs: {}",
                        refs.join(", ")
                    ),
                    "Try fetching from the remote, then make the bookmark point to where you want \
                     it to be, and push again.",
                ),
                GitPushError::RefUpdateRejected(_) => user_error(err),
                GitPushError::InternalGitError(err) => map_git2_error(err),
                GitPushError::Subprocess(_) => user_error(err),
                GitPushError::UnexpectedBackend(_) => user_error(err),
            }
        }
    }

    impl From<GitRemoteManagementError> for CommandError {
        fn from(err: GitRemoteManagementError) -> Self {
            user_error(err)
        }
    }

    impl From<GitConfigParseError> for CommandError {
        fn from(err: GitConfigParseError) -> Self {
            internal_error_with_message("Failed to parse Git config", err)
        }
    }

    impl From<UnexpectedGitBackendError> for CommandError {
        fn from(err: UnexpectedGitBackendError) -> Self {
            user_error(err)
        }
    }

    fn map_git2_error(err: git2::Error) -> CommandError {
        if err.class() == git2::ErrorClass::Ssh {
            let hint = if err.code() == git2::ErrorCode::Certificate
                && std::env::var_os("HOME").is_none()
            {
                "The HOME environment variable is not set, and might be required for Git to \
                 successfully load certificates. Try setting it to the path of a directory that \
                 contains a `.ssh` directory."
            } else {
                "Jujutsu uses libssh2, which doesn't respect ~/.ssh/config. Does `ssh -F \
                 /dev/null` to the host work?"
            };

            user_error_with_hint(err, hint)
        } else {
            user_error(err)
        }
    }
}

impl From<RevsetEvaluationError> for CommandError {
    fn from(err: RevsetEvaluationError) -> Self {
        user_error(err)
    }
}

impl From<FilesetParseError> for CommandError {
    fn from(err: FilesetParseError) -> Self {
        let hint = fileset_parse_error_hint(&err);
        let mut cmd_err =
            user_error_with_message(format!("Failed to parse fileset: {}", err.kind()), err);
        cmd_err.extend_hints(hint);
        cmd_err
    }
}

impl From<RecoverWorkspaceError> for CommandError {
    fn from(err: RecoverWorkspaceError) -> Self {
        match err {
            RecoverWorkspaceError::Backend(err) => err.into(),
            RecoverWorkspaceError::OpHeadsStore(err) => err.into(),
            RecoverWorkspaceError::Reset(err) => err.into(),
            RecoverWorkspaceError::RewriteRootCommit(err) => err.into(),
            err @ RecoverWorkspaceError::WorkspaceMissingWorkingCopy(_) => user_error(err),
        }
    }
}

impl From<RevsetParseError> for CommandError {
    fn from(err: RevsetParseError) -> Self {
        let hint = revset_parse_error_hint(&err);
        let mut cmd_err =
            user_error_with_message(format!("Failed to parse revset: {}", err.kind()), err);
        cmd_err.extend_hints(hint);
        cmd_err
    }
}

impl From<RevsetResolutionError> for CommandError {
    fn from(err: RevsetResolutionError) -> Self {
        let hint = revset_resolution_error_hint(&err);
        let mut cmd_err = user_error(err);
        cmd_err.extend_hints(hint);
        cmd_err
    }
}

impl From<UserRevsetEvaluationError> for CommandError {
    fn from(err: UserRevsetEvaluationError) -> Self {
        match err {
            UserRevsetEvaluationError::Resolution(err) => err.into(),
            UserRevsetEvaluationError::Evaluation(err) => err.into(),
        }
    }
}

impl From<TemplateParseError> for CommandError {
    fn from(err: TemplateParseError) -> Self {
        let hint = template_parse_error_hint(&err);
        let mut cmd_err =
            user_error_with_message(format!("Failed to parse template: {}", err.kind()), err);
        cmd_err.extend_hints(hint);
        cmd_err
    }
}

impl From<UiPathParseError> for CommandError {
    fn from(err: UiPathParseError) -> Self {
        user_error(err)
    }
}

impl From<clap::Error> for CommandError {
    fn from(err: clap::Error) -> Self {
        let hint = find_source_parse_error_hint(&err);
        let mut cmd_err = cli_error(err);
        cmd_err.extend_hints(hint);
        cmd_err
    }
}

impl From<WorkingCopyStateError> for CommandError {
    fn from(err: WorkingCopyStateError) -> Self {
        internal_error_with_message("Failed to access working copy state", err)
    }
}

impl From<GitIgnoreError> for CommandError {
    fn from(err: GitIgnoreError) -> Self {
        user_error_with_message("Failed to process .gitignore.", err)
    }
}

impl From<ParseBulkEditMessageError> for CommandError {
    fn from(err: ParseBulkEditMessageError) -> Self {
        user_error(err)
    }
}

impl From<AbsorbError> for CommandError {
    fn from(err: AbsorbError) -> Self {
        match err {
            AbsorbError::Backend(err) => err.into(),
            AbsorbError::RevsetEvaluation(err) => err.into(),
        }
    }
}

fn find_source_parse_error_hint(err: &dyn error::Error) -> Option<String> {
    let source = err.source()?;
    if let Some(source) = source.downcast_ref() {
        config_get_error_hint(source)
    } else if let Some(source) = source.downcast_ref() {
        file_pattern_parse_error_hint(source)
    } else if let Some(source) = source.downcast_ref() {
        fileset_parse_error_hint(source)
    } else if let Some(source) = source.downcast_ref() {
        revset_parse_error_hint(source)
    } else if let Some(source) = source.downcast_ref() {
        revset_resolution_error_hint(source)
    } else if let Some(UserRevsetEvaluationError::Resolution(source)) = source.downcast_ref() {
        revset_resolution_error_hint(source)
    } else if let Some(source) = source.downcast_ref() {
        string_pattern_parse_error_hint(source)
    } else if let Some(source) = source.downcast_ref() {
        template_parse_error_hint(source)
    } else {
        None
    }
}

fn config_get_error_hint(err: &ConfigGetError) -> Option<String> {
    match &err {
        ConfigGetError::NotFound { .. } => None,
        ConfigGetError::Type { source_path, .. } => source_path
            .as_ref()
            .map(|path| format!("Check the config file: {}", path.display())),
    }
}

fn file_pattern_parse_error_hint(err: &FilePatternParseError) -> Option<String> {
    match err {
        FilePatternParseError::InvalidKind(_) => None,
        // Suggest root:"<path>" if input can be parsed as repo-relative path
        FilePatternParseError::UiPath(UiPathParseError::Fs(e)) => {
            RepoPathBuf::from_relative_path(&e.input).ok().map(|path| {
                format!(r#"Consider using root:{path:?} to specify repo-relative path"#)
            })
        }
        FilePatternParseError::RelativePath(_) => None,
        FilePatternParseError::GlobPattern(_) => None,
    }
}

fn fileset_parse_error_hint(err: &FilesetParseError) -> Option<String> {
    match err.kind() {
        FilesetParseErrorKind::SyntaxError => Some(String::from(
            "See https://jj-vcs.github.io/jj/latest/filesets/ for filesets syntax, or for how to \
             match file paths.",
        )),
        FilesetParseErrorKind::NoSuchFunction {
            name: _,
            candidates,
        } => format_similarity_hint(candidates),
        FilesetParseErrorKind::InvalidArguments { .. } | FilesetParseErrorKind::Expression(_) => {
            find_source_parse_error_hint(&err)
        }
    }
}

fn opset_resolution_error_hint(err: &OpsetResolutionError) -> Option<String> {
    match err {
        OpsetResolutionError::MultipleOperations {
            expr: _,
            candidates,
        } => Some(format!(
            "Try specifying one of the operations by ID: {}",
            candidates.iter().map(short_operation_hash).join(", ")
        )),
        OpsetResolutionError::EmptyOperations(_)
        | OpsetResolutionError::InvalidIdPrefix(_)
        | OpsetResolutionError::NoSuchOperation(_)
        | OpsetResolutionError::AmbiguousIdPrefix(_) => None,
    }
}

fn revset_parse_error_hint(err: &RevsetParseError) -> Option<String> {
    // Only for the bottom error, which is usually the root cause
    let bottom_err = iter::successors(Some(err), |e| e.origin()).last().unwrap();
    match bottom_err.kind() {
        RevsetParseErrorKind::NotPrefixOperator {
            op: _,
            similar_op,
            description,
        }
        | RevsetParseErrorKind::NotPostfixOperator {
            op: _,
            similar_op,
            description,
        }
        | RevsetParseErrorKind::NotInfixOperator {
            op: _,
            similar_op,
            description,
        } => Some(format!("Did you mean `{similar_op}` for {description}?")),
        RevsetParseErrorKind::NoSuchFunction {
            name: _,
            candidates,
        } => format_similarity_hint(candidates),
        RevsetParseErrorKind::InvalidFunctionArguments { .. }
        | RevsetParseErrorKind::Expression(_) => find_source_parse_error_hint(bottom_err),
        _ => None,
    }
}

fn revset_resolution_error_hint(err: &RevsetResolutionError) -> Option<String> {
    match err {
        RevsetResolutionError::NoSuchRevision {
            name: _,
            candidates,
        } => format_similarity_hint(candidates),
        RevsetResolutionError::EmptyString
        | RevsetResolutionError::WorkspaceMissingWorkingCopy { .. }
        | RevsetResolutionError::AmbiguousCommitIdPrefix(_)
        | RevsetResolutionError::AmbiguousChangeIdPrefix(_)
        | RevsetResolutionError::StoreError(_)
        | RevsetResolutionError::Other(_) => None,
    }
}

fn string_pattern_parse_error_hint(err: &StringPatternParseError) -> Option<String> {
    match err {
        StringPatternParseError::InvalidKind(_) => {
            Some("Try prefixing with one of `exact:`, `glob:`, `regex:`, or `substring:`".into())
        }
        StringPatternParseError::GlobPattern(_) | StringPatternParseError::Regex(_) => None,
    }
}

fn template_parse_error_hint(err: &TemplateParseError) -> Option<String> {
    // Only for the bottom error, which is usually the root cause
    let bottom_err = iter::successors(Some(err), |e| e.origin()).last().unwrap();
    match bottom_err.kind() {
        TemplateParseErrorKind::NoSuchKeyword { candidates, .. }
        | TemplateParseErrorKind::NoSuchFunction { candidates, .. }
        | TemplateParseErrorKind::NoSuchMethod { candidates, .. } => {
            format_similarity_hint(candidates)
        }
        TemplateParseErrorKind::InvalidArguments { .. } | TemplateParseErrorKind::Expression(_) => {
            find_source_parse_error_hint(bottom_err)
        }
        _ => None,
    }
}

const BROKEN_PIPE_EXIT_CODE: u8 = 3;

pub(crate) fn handle_command_result(ui: &mut Ui, result: Result<(), CommandError>) -> ExitCode {
    try_handle_command_result(ui, result).unwrap_or_else(|_| ExitCode::from(BROKEN_PIPE_EXIT_CODE))
}

fn try_handle_command_result(
    ui: &mut Ui,
    result: Result<(), CommandError>,
) -> io::Result<ExitCode> {
    let Err(cmd_err) = &result else {
        return Ok(ExitCode::SUCCESS);
    };
    let err = &cmd_err.error;
    let hints = &cmd_err.hints;
    match cmd_err.kind {
        CommandErrorKind::User => {
            print_error(ui, "Error: ", err, hints)?;
            Ok(ExitCode::from(1))
        }
        CommandErrorKind::Config => {
            print_error(ui, "Config error: ", err, hints)?;
            writeln!(
                ui.stderr_formatter().labeled("hint"),
                "For help, see https://jj-vcs.github.io/jj/latest/config/."
            )?;
            Ok(ExitCode::from(1))
        }
        CommandErrorKind::Cli => {
            if let Some(err) = err.downcast_ref::<clap::Error>() {
                handle_clap_error(ui, err, hints)
            } else {
                print_error(ui, "Error: ", err, hints)?;
                Ok(ExitCode::from(2))
            }
        }
        CommandErrorKind::BrokenPipe => {
            // A broken pipe is not an error, but a signal to exit gracefully.
            Ok(ExitCode::from(BROKEN_PIPE_EXIT_CODE))
        }
        CommandErrorKind::Internal => {
            print_error(ui, "Internal error: ", err, hints)?;
            Ok(ExitCode::from(255))
        }
    }
}

fn print_error(
    ui: &Ui,
    heading: &str,
    err: &dyn error::Error,
    hints: &[ErrorHint],
) -> io::Result<()> {
    writeln!(ui.error_with_heading(heading), "{err}")?;
    print_error_sources(ui, err.source())?;
    print_error_hints(ui, hints)?;
    Ok(())
}

fn print_error_sources(ui: &Ui, source: Option<&dyn error::Error>) -> io::Result<()> {
    let Some(err) = source else {
        return Ok(());
    };
    ui.stderr_formatter()
        .with_label("error_source", |formatter| {
            if err.source().is_none() {
                write!(formatter.labeled("heading"), "Caused by: ")?;
                writeln!(formatter, "{err}")?;
            } else {
                writeln!(formatter.labeled("heading"), "Caused by:")?;
                for (i, err) in iter::successors(Some(err), |err| err.source()).enumerate() {
                    write!(formatter.labeled("heading"), "{}: ", i + 1)?;
                    writeln!(formatter, "{err}")?;
                }
            }
            Ok(())
        })
}

fn print_error_hints(ui: &Ui, hints: &[ErrorHint]) -> io::Result<()> {
    for hint in hints {
        ui.stderr_formatter().with_label("hint", |formatter| {
            write!(formatter.labeled("heading"), "Hint: ")?;
            match hint {
                ErrorHint::PlainText(message) => {
                    writeln!(formatter, "{message}")?;
                }
                ErrorHint::Formatted(recorded) => {
                    recorded.replay(formatter)?;
                    // Formatted hint is usually multi-line text, and it's
                    // convenient if trailing "\n" doesn't have to be omitted.
                    if !recorded.data().ends_with(b"\n") {
                        writeln!(formatter)?;
                    }
                }
            }
            io::Result::Ok(())
        })?;
    }
    Ok(())
}

fn handle_clap_error(ui: &mut Ui, err: &clap::Error, hints: &[ErrorHint]) -> io::Result<ExitCode> {
    let clap_str = if ui.color() {
        err.render().ansi().to_string()
    } else {
        err.render().to_string()
    };

    match err.kind() {
        clap::error::ErrorKind::DisplayHelp
        | clap::error::ErrorKind::DisplayHelpOnMissingArgumentOrSubcommand => ui.request_pager(),
        _ => {}
    };
    // Definitions for exit codes and streams come from
    // https://github.com/clap-rs/clap/blob/master/src/error/mod.rs
    match err.kind() {
        clap::error::ErrorKind::DisplayHelp | clap::error::ErrorKind::DisplayVersion => {
            write!(ui.stdout(), "{clap_str}")?;
            return Ok(ExitCode::SUCCESS);
        }
        _ => {}
    }
    write!(ui.stderr(), "{clap_str}")?;
    print_error_hints(ui, hints)?;
    Ok(ExitCode::from(2))
}

/// Prints diagnostic messages emitted during parsing.
pub fn print_parse_diagnostics<T: error::Error>(
    ui: &Ui,
    context_message: &str,
    diagnostics: &Diagnostics<T>,
) -> io::Result<()> {
    for diag in diagnostics {
        writeln!(ui.warning_default(), "{context_message}")?;
        for err in iter::successors(Some(diag as &dyn error::Error), |err| err.source()) {
            writeln!(ui.stderr(), "{err}")?;
        }
        // If we add support for multiple error diagnostics, we might have to do
        // find_source_parse_error_hint() and print it here.
    }
    Ok(())
}