use crate::completions::{
    CommandCompletion, Completer, CompletionOptions, CustomCompletion, DirectoryCompletion,
    DotNuCompletion, FileCompletion, FlagCompletion, VariableCompletion,
};
use nu_color_config::{color_record_to_nustyle, lookup_ansi_color_style};
use nu_engine::eval_block;
use nu_parser::{flatten_pipeline_element, parse, FlatShape};
use nu_protocol::{
    debugger::WithoutDebug,
    engine::{Closure, EngineState, Stack, StateWorkingSet},
    PipelineData, Span, Value,
};
use reedline::{Completer as ReedlineCompleter, Suggestion};
use std::{str, sync::Arc};

use super::base::{SemanticSuggestion, SuggestionKind};

#[derive(Clone)]
pub struct NuCompleter {
    engine_state: Arc<EngineState>,
    stack: Stack,
}

impl NuCompleter {
    pub fn new(engine_state: Arc<EngineState>, stack: Arc<Stack>) -> Self {
        Self {
            engine_state,
            stack: Stack::with_parent(stack).reset_out_dest().capture(),
        }
    }

    pub fn fetch_completions_at(&mut self, line: &str, pos: usize) -> Vec<SemanticSuggestion> {
        self.completion_helper(line, pos)
    }

    // Process the completion for a given completer
    fn process_completion<T: Completer>(
        &self,
        completer: &mut T,
        working_set: &StateWorkingSet,
        prefix: Vec<u8>,
        new_span: Span,
        offset: usize,
        pos: usize,
    ) -> Vec<SemanticSuggestion> {
        let config = self.engine_state.get_config();

        let options = CompletionOptions {
            case_sensitive: config.case_sensitive_completions,
            match_algorithm: config.completion_algorithm.into(),
            ..Default::default()
        };

        // Fetch
        let mut suggestions = completer.fetch(
            working_set,
            &self.stack,
            prefix.clone(),
            new_span,
            offset,
            pos,
            &options,
        );

        // Sort
        suggestions = completer.sort(suggestions, prefix);

        suggestions
    }

    fn external_completion(
        &self,
        closure: &Closure,
        spans: &[String],
        offset: usize,
        span: Span,
    ) -> Option<Vec<SemanticSuggestion>> {
        let block = self.engine_state.get_block(closure.block_id);
        let mut callee_stack = self
            .stack
            .captures_to_stack_preserve_out_dest(closure.captures.clone());

        // Line
        if let Some(pos_arg) = block.signature.required_positional.first() {
            if let Some(var_id) = pos_arg.var_id {
                callee_stack.add_var(
                    var_id,
                    Value::list(
                        spans
                            .iter()
                            .map(|it| Value::string(it, Span::unknown()))
                            .collect(),
                        Span::unknown(),
                    ),
                );
            }
        }

        let result = eval_block::<WithoutDebug>(
            &self.engine_state,
            &mut callee_stack,
            block,
            PipelineData::empty(),
        );

        match result.and_then(|data| data.into_value(span)) {
            Ok(value) => {
                if let Value::List { vals, .. } = value {
                    let result =
                        map_value_completions(vals.iter(), Span::new(span.start, span.end), offset);

                    return Some(result);
                }
            }
            Err(err) => println!("failed to eval completer block: {err}"),
        }

        None
    }

    fn completion_helper(&mut self, line: &str, pos: usize) -> Vec<SemanticSuggestion> {
        let mut working_set = StateWorkingSet::new(&self.engine_state);
        let offset = working_set.next_span_start();
        // TODO: Callers should be trimming the line themselves
        let line = if line.len() > pos { &line[..pos] } else { line };
        // Adjust offset so that the spans of the suggestions will start at the right
        // place even with `only_buffer_difference: true`
        let fake_offset = offset + line.len() - pos;
        let pos = offset + line.len();
        let initial_line = line.to_string();
        let mut line = line.to_string();
        line.push('a');

        let config = self.engine_state.get_config();

        let output = parse(&mut working_set, Some("completer"), line.as_bytes(), false);

        for pipeline in &output.pipelines {
            for pipeline_element in &pipeline.elements {
                let flattened = flatten_pipeline_element(&working_set, pipeline_element);
                let mut spans: Vec<String> = vec![];

                for (flat_idx, flat) in flattened.iter().enumerate() {
                    let is_passthrough_command = spans
                        .first()
                        .filter(|content| content.as_str() == "sudo" || content.as_str() == "doas")
                        .is_some();
                    // Read the current spam to string
                    let current_span = working_set.get_span_contents(flat.0).to_vec();
                    let current_span_str = String::from_utf8_lossy(&current_span);

                    let is_last_span = pos >= flat.0.start && pos < flat.0.end;

                    // Skip the last 'a' as span item
                    if is_last_span {
                        let offset = pos - flat.0.start;
                        if offset == 0 {
                            spans.push(String::new())
                        } else {
                            let mut current_span_str = current_span_str.to_string();
                            current_span_str.remove(offset);
                            spans.push(current_span_str);
                        }
                    } else {
                        spans.push(current_span_str.to_string());
                    }

                    // Complete based on the last span
                    if is_last_span {
                        // Context variables
                        let most_left_var =
                            most_left_variable(flat_idx, &working_set, flattened.clone());

                        // Create a new span
                        let new_span = Span::new(flat.0.start, flat.0.end - 1);

                        // Parses the prefix. Completion should look up to the cursor position, not after.
                        let mut prefix = working_set.get_span_contents(flat.0).to_vec();
                        let index = pos - flat.0.start;
                        prefix.drain(index..);

                        // Variables completion
                        if prefix.starts_with(b"$") || most_left_var.is_some() {
                            let mut completer =
                                VariableCompletion::new(most_left_var.unwrap_or((vec![], vec![])));

                            return self.process_completion(
                                &mut completer,
                                &working_set,
                                prefix,
                                new_span,
                                fake_offset,
                                pos,
                            );
                        }

                        // Flags completion
                        if prefix.starts_with(b"-") {
                            // Try to complete flag internally
                            let mut completer = FlagCompletion::new(pipeline_element.expr.clone());
                            let result = self.process_completion(
                                &mut completer,
                                &working_set,
                                prefix.clone(),
                                new_span,
                                fake_offset,
                                pos,
                            );

                            if !result.is_empty() {
                                return result;
                            }

                            // We got no results for internal completion
                            // now we can check if external completer is set and use it
                            if let Some(closure) = config.external_completer.as_ref() {
                                if let Some(external_result) =
                                    self.external_completion(closure, &spans, fake_offset, new_span)
                                {
                                    return external_result;
                                }
                            }
                        }

                        // specially check if it is currently empty - always complete commands
                        if (is_passthrough_command && flat_idx == 1)
                            || (flat_idx == 0 && working_set.get_span_contents(new_span).is_empty())
                        {
                            let mut completer = CommandCompletion::new(
                                flattened.clone(),
                                // flat_idx,
                                FlatShape::String,
                                true,
                            );
                            return self.process_completion(
                                &mut completer,
                                &working_set,
                                prefix,
                                new_span,
                                fake_offset,
                                pos,
                            );
                        }

                        // Completions that depends on the previous expression (e.g: use, source-env)
                        if (is_passthrough_command && flat_idx > 1) || flat_idx > 0 {
                            if let Some(previous_expr) = flattened.get(flat_idx - 1) {
                                // Read the content for the previous expression
                                let prev_expr_str =
                                    working_set.get_span_contents(previous_expr.0).to_vec();

                                // Completion for .nu files
                                if prev_expr_str == b"use"
                                    || prev_expr_str == b"overlay use"
                                    || prev_expr_str == b"source-env"
                                {
                                    let mut completer = DotNuCompletion::new();

                                    return self.process_completion(
                                        &mut completer,
                                        &working_set,
                                        prefix,
                                        new_span,
                                        fake_offset,
                                        pos,
                                    );
                                } else if prev_expr_str == b"ls" {
                                    let mut completer = FileCompletion::new();

                                    return self.process_completion(
                                        &mut completer,
                                        &working_set,
                                        prefix,
                                        new_span,
                                        fake_offset,
                                        pos,
                                    );
                                }
                            }
                        }

                        // Match other types
                        match &flat.1 {
                            FlatShape::Custom(decl_id) => {
                                let mut completer = CustomCompletion::new(
                                    self.stack.clone(),
                                    *decl_id,
                                    initial_line,
                                );

                                return self.process_completion(
                                    &mut completer,
                                    &working_set,
                                    prefix,
                                    new_span,
                                    fake_offset,
                                    pos,
                                );
                            }
                            FlatShape::Directory => {
                                let mut completer = DirectoryCompletion::new();

                                return self.process_completion(
                                    &mut completer,
                                    &working_set,
                                    prefix,
                                    new_span,
                                    fake_offset,
                                    pos,
                                );
                            }
                            FlatShape::Filepath | FlatShape::GlobPattern => {
                                let mut completer = FileCompletion::new();

                                return self.process_completion(
                                    &mut completer,
                                    &working_set,
                                    prefix,
                                    new_span,
                                    fake_offset,
                                    pos,
                                );
                            }
                            flat_shape => {
                                let mut completer = CommandCompletion::new(
                                    flattened.clone(),
                                    // flat_idx,
                                    flat_shape.clone(),
                                    false,
                                );

                                let mut out: Vec<_> = self.process_completion(
                                    &mut completer,
                                    &working_set,
                                    prefix.clone(),
                                    new_span,
                                    fake_offset,
                                    pos,
                                );

                                if !out.is_empty() {
                                    return out;
                                }

                                // Try to complete using an external completer (if set)
                                if let Some(closure) = config.external_completer.as_ref() {
                                    if let Some(external_result) = self.external_completion(
                                        closure,
                                        &spans,
                                        fake_offset,
                                        new_span,
                                    ) {
                                        return external_result;
                                    }
                                }

                                // Check for file completion
                                let mut completer = FileCompletion::new();
                                out = self.process_completion(
                                    &mut completer,
                                    &working_set,
                                    prefix,
                                    new_span,
                                    fake_offset,
                                    pos,
                                );

                                if !out.is_empty() {
                                    return out;
                                }
                            }
                        };
                    }
                }
            }
        }

        vec![]
    }
}

impl ReedlineCompleter for NuCompleter {
    fn complete(&mut self, line: &str, pos: usize) -> Vec<Suggestion> {
        self.completion_helper(line, pos)
            .into_iter()
            .map(|s| s.suggestion)
            .collect()
    }
}

// reads the most left variable returning it's name (e.g: $myvar)
// and the depth (a.b.c)
fn most_left_variable(
    idx: usize,
    working_set: &StateWorkingSet<'_>,
    flattened: Vec<(Span, FlatShape)>,
) -> Option<(Vec<u8>, Vec<Vec<u8>>)> {
    // Reverse items to read the list backwards and truncate
    // because the only items that matters are the ones before the current index
    let mut rev = flattened;
    rev.truncate(idx);
    rev = rev.into_iter().rev().collect();

    // Store the variables and sub levels found and reverse to correct order
    let mut variables_found: Vec<Vec<u8>> = vec![];
    let mut found_var = false;
    for item in rev.clone() {
        let result = working_set.get_span_contents(item.0).to_vec();

        match item.1 {
            FlatShape::Variable(_) => {
                variables_found.push(result);
                found_var = true;

                break;
            }
            FlatShape::String => {
                variables_found.push(result);
            }
            _ => {
                break;
            }
        }
    }

    // If most left var was not found
    if !found_var {
        return None;
    }

    // Reverse the order back
    variables_found = variables_found.into_iter().rev().collect();

    // Extract the variable and the sublevels
    let var = variables_found.first().unwrap_or(&vec![]).to_vec();
    let sublevels: Vec<Vec<u8>> = variables_found.into_iter().skip(1).collect();

    Some((var, sublevels))
}

pub fn map_value_completions<'a>(
    list: impl Iterator<Item = &'a Value>,
    span: Span,
    offset: usize,
) -> Vec<SemanticSuggestion> {
    list.filter_map(move |x| {
        // Match for string values
        if let Ok(s) = x.coerce_string() {
            return Some(SemanticSuggestion {
                suggestion: Suggestion {
                    value: s,
                    description: None,
                    style: None,
                    extra: None,
                    span: reedline::Span {
                        start: span.start - offset,
                        end: span.end - offset,
                    },
                    append_whitespace: false,
                },
                kind: Some(SuggestionKind::Type(x.get_type())),
            });
        }

        // Match for record values
        if let Ok(record) = x.as_record() {
            let mut suggestion = Suggestion {
                value: String::from(""), // Initialize with empty string
                description: None,
                style: None,
                extra: None,
                span: reedline::Span {
                    start: span.start - offset,
                    end: span.end - offset,
                },
                append_whitespace: false,
            };

            // Iterate the cols looking for `value` and `description`
            record.iter().for_each(|it| {
                // Match `value` column
                if it.0 == "value" {
                    // Convert the value to string
                    if let Ok(val_str) = it.1.coerce_string() {
                        // Update the suggestion value
                        suggestion.value = val_str;
                    }
                }

                // Match `description` column
                if it.0 == "description" {
                    // Convert the value to string
                    if let Ok(desc_str) = it.1.coerce_string() {
                        // Update the suggestion value
                        suggestion.description = Some(desc_str);
                    }
                }

                // Match `style` column
                if it.0 == "style" {
                    // Convert the value to string
                    suggestion.style = match it.1 {
                        Value::String { val, .. } => Some(lookup_ansi_color_style(val)),
                        Value::Record { .. } => Some(color_record_to_nustyle(it.1)),
                        _ => None,
                    };
                }
            });

            return Some(SemanticSuggestion {
                suggestion,
                kind: Some(SuggestionKind::Type(x.get_type())),
            });
        }

        None
    })
    .collect()
}

#[cfg(test)]
mod completer_tests {
    use super::*;

    #[test]
    fn test_completion_helper() {
        let mut engine_state =
            nu_command::add_shell_command_context(nu_cmd_lang::create_default_context());

        // Custom additions
        let delta = {
            let working_set = nu_protocol::engine::StateWorkingSet::new(&engine_state);
            working_set.render()
        };

        let result = engine_state.merge_delta(delta);
        assert!(
            result.is_ok(),
            "Error merging delta: {:?}",
            result.err().unwrap()
        );

        let mut completer = NuCompleter::new(engine_state.into(), Arc::new(Stack::new()));
        let dataset = [
            ("sudo", false, "", Vec::new()),
            ("sudo l", true, "l", vec!["ls", "let", "lines", "loop"]),
            (" sudo", false, "", Vec::new()),
            (" sudo le", true, "le", vec!["let", "length"]),
            (
                "ls | c",
                true,
                "c",
                vec!["cd", "config", "const", "cp", "cal"],
            ),
            ("ls | sudo m", true, "m", vec!["mv", "mut", "move"]),
        ];
        for (line, has_result, begins_with, expected_values) in dataset {
            let result = completer.completion_helper(line, line.len());
            // Test whether the result is empty or not
            assert_eq!(!result.is_empty(), has_result, "line: {}", line);

            // Test whether the result begins with the expected value
            result
                .iter()
                .for_each(|x| assert!(x.suggestion.value.starts_with(begins_with)));

            // Test whether the result contains all the expected values
            assert_eq!(
                result
                    .iter()
                    .map(|x| expected_values.contains(&x.suggestion.value.as_str()))
                    .filter(|x| *x)
                    .count(),
                expected_values.len(),
                "line: {}",
                line
            );
        }
    }
}