use std::path::{Path, PathBuf};

use super::util::try_interaction;
use itertools::Itertools;
use nu_engine::env::current_dir;
use nu_engine::CallExt;
use nu_glob::GlobResult;
use nu_path::dots::expand_ndots;
use nu_protocol::ast::Call;
use nu_protocol::engine::{Command, EngineState, Stack};
use nu_protocol::{
    Category, Example, IntoInterruptiblePipelineData, PipelineData, ShellError, Signature, Span,
    Spanned, SyntaxShape, Value,
};

const GLOB_PARAMS: nu_glob::MatchOptions = nu_glob::MatchOptions {
    case_sensitive: true,
    require_literal_separator: false,
    require_literal_leading_dot: false,
    recursive_match_hidden_dir: true,
};

#[derive(Clone)]
pub struct Mv;

#[allow(unused_must_use)]
impl Command for Mv {
    fn name(&self) -> &str {
        "mv"
    }

    fn usage(&self) -> &str {
        "Move files or directories."
    }

    fn search_terms(&self) -> Vec<&str> {
        vec!["mv", "move"]
    }

    fn signature(&self) -> nu_protocol::Signature {
        Signature::build("mv")
            .rest(
                "source(s)",
                SyntaxShape::String,
                "the location(s) to move files/directories from",
            )
            // .required(
            //     "source",
            //     SyntaxShape::GlobPattern,
            //     "the location to move files/directories from",
            // )
            .required(
                "destination",
                SyntaxShape::Filepath,
                "the location to move files/directories to",
            )
            .switch(
                "verbose",
                "make mv to be verbose, showing files been moved.",
                Some('v'),
            )
            .switch("interactive", "ask user to confirm action", Some('i'))
            // .switch("force", "suppress error when no file", Some('f'))
            .category(Category::FileSystem)
    }

    fn run(
        &self,
        engine_state: &EngineState,
        stack: &mut Stack,
        call: &Call,
        _input: PipelineData,
    ) -> Result<nu_protocol::PipelineData, nu_protocol::ShellError> {
        // TODO: handle invalid directory or insufficient permissions when moving
        let mut spanned_sources: Vec<Spanned<String>> = call.rest(engine_state, stack, 0)?;
        // read destination as final argument
        let spanned_destination: Spanned<String> =
            call.req(engine_state, stack, spanned_sources.len() - 1)?;
        // don't read destination argument
        spanned_sources.pop();
        let verbose = call.has_flag("verbose");
        let interactive = call.has_flag("interactive");
        // let force = call.has_flag("force");

        let ctrlc = engine_state.ctrlc.clone();

        let path = current_dir(engine_state, stack)?;

        let span = call.head;

        Ok(spanned_sources
            .into_iter()
            .flat_map(move |spanned_source| {
                let path = path.clone();
                let source = path.join(spanned_source.item.as_str());
                let destination = expand_ndots(path.join(spanned_destination.item.as_str()));

                let mut sources: Vec<GlobResult> =
                    nu_glob::glob_with(&source.to_string_lossy(), GLOB_PARAMS)
                        .map_or_else(|_| Vec::new(), Iterator::collect);

                if sources.is_empty() {
                    let err = ShellError::GenericError(
                        "Invalid file or pattern".into(),
                        "invalid file or pattern".into(),
                        Some(spanned_source.span),
                        None,
                        Vec::new(),
                    );
                    return Vec::from([Value::Error { error: err }]).into_iter();
                }

                // We have two possibilities.
                //
                // First, the destination exists.
                //  - If a directory, move everything into that directory, otherwise
                //  - if only a single source, overwrite the file, otherwise
                //  - error.
                //
                // Second, the destination doesn't exist, so we can only rename a single source. Otherwise
                // it's an error.

                if (destination.exists() && !destination.is_dir() && sources.len() > 1)
                    || (!destination.exists() && sources.len() > 1)
                {
                    let err = ShellError::GenericError(
                        "Can only move multiple sources if destination is a directory".into(),
                        "destination must be a directory when multiple sources".into(),
                        Some(spanned_destination.span),
                        None,
                        Vec::new(),
                    );
                    return Vec::from([Value::Error { error: err }]).into_iter();
                }

                let some_if_source_is_destination = sources
                    .iter()
                    .find(|f| matches!(f, Ok(f) if destination.starts_with(f)));
                if destination.exists() && destination.is_dir() && sources.len() == 1 {
                    if let Some(Ok(filename)) = some_if_source_is_destination {
                        let err = ShellError::GenericError(
                            format!(
                                "Not possible to move {:?} to itself",
                                filename.file_name().unwrap_or(filename.as_os_str())
                            ),
                            "cannot move to itself".into(),
                            Some(spanned_destination.span),
                            None,
                            Vec::new(),
                        );
                        return Vec::from([Value::Error { error: err }]).into_iter();
                    }
                }

                if let Some(Ok(_filename)) = some_if_source_is_destination {
                    sources = sources
                        .into_iter()
                        .filter(|f| matches!(f, Ok(f) if !destination.starts_with(f)))
                        .collect();
                }

                sources
                    .into_iter()
                    .flatten()
                    .filter_map(move |entry| {
                        let entry = expand_ndots(entry);
                        let result = move_file(
                            Spanned {
                                item: entry.clone(),
                                span: spanned_source.span,
                            },
                            Spanned {
                                item: destination.clone(),
                                span: spanned_destination.span,
                            },
                            interactive,
                        );
                        if let Err(error) = result {
                            Some(Value::Error { error })
                        } else if verbose {
                            let val = match result {
                                Ok(true) => format!(
                                    "moved {:} to {:}",
                                    entry.to_string_lossy(),
                                    destination.to_string_lossy()
                                ),
                                _ => format!(
                                    "{:} not moved to {:}",
                                    entry.to_string_lossy(),
                                    destination.to_string_lossy()
                                ),
                            };
                            Some(Value::String { val, span })
                        } else {
                            None
                        }
                    })
                    .collect_vec()
                    .into_iter()
            })
            .into_pipeline_data(ctrlc))
    }

    fn examples(&self) -> Vec<Example> {
        vec![
            Example {
                description: "Rename a file",
                example: "mv before.txt after.txt",
                result: None,
            },
            Example {
                description: "Move a file into a directory",
                example: "mv test.txt my/subdirectory",
                result: None,
            },
            Example {
                description: "Move many files into a directory",
                example: "mv *.txt my/subdirectory",
                result: None,
            },
        ]
    }
}

fn move_file(
    spanned_from: Spanned<PathBuf>,
    spanned_to: Spanned<PathBuf>,
    interactive: bool,
) -> Result<bool, ShellError> {
    let Spanned {
        item: from,
        span: from_span,
    } = spanned_from;
    let Spanned {
        item: to,
        span: to_span,
    } = spanned_to;

    if to.exists() && from.is_dir() && to.is_file() {
        return Err(ShellError::MoveNotPossible {
            source_message: "Can't move a directory".to_string(),
            source_span: spanned_from.span,
            destination_message: "to a file".to_string(),
            destination_span: spanned_to.span,
        });
    }

    let destination_dir_exists = if to.is_dir() {
        true
    } else {
        to.parent().map(Path::exists).unwrap_or(true)
    };

    if !destination_dir_exists {
        return Err(ShellError::DirectoryNotFound(to_span, None));
    }

    let mut to = to;
    if to.is_dir() {
        let from_file_name = match from.file_name() {
            Some(name) => name,
            None => return Err(ShellError::DirectoryNotFound(to_span, None)),
        };

        to.push(from_file_name);
    }

    if interactive && to.exists() {
        let (interaction, confirmed) =
            try_interaction(interactive, "mv: overwrite", &to.to_string_lossy());
        if let Err(e) = interaction {
            return Err(ShellError::GenericError(
                format!("Error during interaction: {:}", e),
                "could not move".into(),
                None,
                None,
                Vec::new(),
            ));
        } else if !confirmed {
            return Ok(false);
        }
    }

    match move_item(&from, from_span, &to) {
        Ok(()) => Ok(true),
        Err(e) => Err(e),
    }
}

fn move_item(from: &Path, from_span: Span, to: &Path) -> Result<(), ShellError> {
    // We first try a rename, which is a quick operation. If that doesn't work, we'll try a copy
    // and remove the old file/folder. This is necessary if we're moving across filesystems or devices.
    std::fs::rename(&from, &to).or_else(|_| {
        match if from.is_file() {
            let mut options = fs_extra::file::CopyOptions::new();
            options.overwrite = true;
            fs_extra::file::move_file(from, to, &options)
        } else {
            let mut options = fs_extra::dir::CopyOptions::new();
            options.overwrite = true;
            options.copy_inside = true;
            fs_extra::dir::move_dir(from, to, &options)
        } {
            Ok(_) => Ok(()),
            Err(e) => Err(ShellError::GenericError(
                format!("Could not move {:?} to {:?}. {:}", from, to, e),
                "could not move".into(),
                Some(from_span),
                None,
                Vec::new(),
            )),
        }
    })
}