use crate::context::CommandRegistry;

use derive_new::new;
use rustyline::completion::{Completer, FilenameCompleter};
use std::path::PathBuf;

#[derive(new)]
pub(crate) struct NuCompleter {
    pub file_completer: FilenameCompleter,
    pub commands: CommandRegistry,
    pub homedir: Option<PathBuf>,
}

impl NuCompleter {
    pub fn complete(
        &self,
        line: &str,
        pos: usize,
        context: &rustyline::Context,
    ) -> rustyline::Result<(usize, Vec<rustyline::completion::Pair>)> {
        let commands: Vec<String> = self.commands.names();

        let line_chars: Vec<_> = line[..pos].chars().collect();

        let mut replace_pos = line_chars.len();
        while replace_pos > 0 {
            if line_chars[replace_pos - 1] == ' ' {
                break;
            }
            replace_pos -= 1;
        }

        let mut completions;

        // See if we're a flag
        if pos > 0 && replace_pos < line_chars.len() && line_chars[replace_pos] == '-' {
            if let Ok(lite_pipeline) = nu_parser::lite_parse(line, 0) {
                completions = self.get_matching_arguments(
                    &lite_pipeline,
                    &line_chars,
                    line,
                    replace_pos,
                    pos,
                );
            } else {
                completions = self.file_completer.complete(line, pos, context)?.1;
            }
        } else {
            completions = self.file_completer.complete(line, pos, context)?.1;

            for completion in &mut completions {
                if completion.replacement.contains("\\ ") {
                    completion.replacement = completion.replacement.replace("\\ ", " ");
                }
                if completion.replacement.contains("\\(") {
                    completion.replacement = completion.replacement.replace("\\(", "(");
                }

                if completion.replacement.contains(' ') || completion.replacement.contains('(') {
                    if !completion.replacement.starts_with('\"') {
                        completion.replacement = format!("\"{}", completion.replacement);
                    }
                    if !completion.replacement.ends_with('\"') {
                        completion.replacement = format!("{}\"", completion.replacement);
                    }
                }
            }
        };

        for command in commands.iter() {
            let mut pos = replace_pos;
            let mut matched = true;
            if pos < line_chars.len() {
                for chr in command.chars() {
                    if line_chars[pos] != chr {
                        matched = false;
                        break;
                    }
                    pos += 1;
                    if pos == line_chars.len() {
                        break;
                    }
                }
            }

            if matched {
                completions.push(rustyline::completion::Pair {
                    display: command.clone(),
                    replacement: command.clone(),
                });
            }
        }

        Ok((replace_pos, completions))
    }

    fn get_matching_arguments(
        &self,
        lite_parse: &nu_parser::LitePipeline,
        line_chars: &[char],
        line: &str,
        replace_pos: usize,
        pos: usize,
    ) -> Vec<rustyline::completion::Pair> {
        let mut matching_arguments = vec![];

        let mut line_copy = line.to_string();
        let substring = line_chars[replace_pos..pos].iter().collect::<String>();
        let replace_string = (replace_pos..pos).map(|_| " ").collect::<String>();
        line_copy.replace_range(replace_pos..pos, &replace_string);

        let result = nu_parser::classify_pipeline(&lite_parse, &self.commands);

        for command in result.commands.list {
            if let nu_protocol::hir::ClassifiedCommand::Internal(
                nu_protocol::hir::InternalCommand { args, .. },
            ) = command
            {
                if replace_pos >= args.span.start() && replace_pos <= args.span.end() {
                    if let Some(named) = args.named {
                        for (name, _) in named.iter() {
                            let full_flag = format!("--{}", name);

                            if full_flag.starts_with(&substring) {
                                matching_arguments.push(rustyline::completion::Pair {
                                    display: full_flag.clone(),
                                    replacement: full_flag,
                                });
                            }
                        }
                    }
                }
            }
        }

        matching_arguments
    }
}