use nu_engine::CallExt;
use nu_protocol::ast::Call;
use nu_protocol::engine::{Command, EngineState, Stack};
use nu_protocol::{
    Category, Example, PipelineData, ShellError, Signature, Span, Spanned, SyntaxShape, Type,
    Value, ValueStream,
};
use regex::Regex;

#[derive(Clone)]
pub struct Parse;

impl Command for Parse {
    fn name(&self) -> &str {
        "parse"
    }

    fn usage(&self) -> &str {
        "Parse columns from string data using a simple pattern."
    }

    fn signature(&self) -> nu_protocol::Signature {
        Signature::build("parse")
            .required(
                "pattern",
                SyntaxShape::String,
                "the pattern to match. Eg) \"{foo}: {bar}\"",
            )
            .switch("regex", "use full regex syntax for patterns", Some('r'))
            .category(Category::Strings)
    }

    fn examples(&self) -> Vec<Example> {
        let result = Value::List {
            vals: vec![Value::Record {
                cols: vec!["foo".to_string(), "bar".to_string()],
                vals: vec![Value::test_string("hi"), Value::test_string("there")],
                span: Span::unknown(),
            }],
            span: Span::unknown(),
        };

        vec![
            Example {
                description: "Parse a string into two named columns",
                example: "echo \"hi there\" | parse \"{foo} {bar}\"",
                result: Some(result.clone()),
            },
            Example {
                description: "Parse a string using regex pattern",
                example: "echo \"hi there\" | parse -r \"(?P<foo>\\w+) (?P<bar>\\w+)\"",
                result: Some(result),
            },
        ]
    }

    fn run(
        &self,
        engine_state: &EngineState,
        stack: &mut Stack,
        call: &Call,
        input: PipelineData,
    ) -> Result<PipelineData, ShellError> {
        operate(engine_state, stack, call, input)
    }
}

fn operate(
    engine_state: &EngineState,
    stack: &mut Stack,
    call: &Call,
    input: PipelineData,
) -> Result<PipelineData, ShellError> {
    let head = call.head;
    let pattern: Spanned<String> = call.req(engine_state, stack, 0)?;
    let regex: bool = call.has_flag("regex");

    let pattern_item = pattern.item;
    let pattern_span = pattern.span;

    let item_to_parse = if regex {
        pattern_item
    } else {
        build_regex(&pattern_item, pattern_span)?
    };

    let regex_pattern =
        Regex::new(&item_to_parse).map_err(|e| parse_regex_error(e, pattern_span))?;

    let columns = column_names(&regex_pattern);
    let mut parsed: Vec<Value> = Vec::new();

    for v in input {
        match v.as_string() {
            Ok(s) => {
                let results = regex_pattern.captures_iter(&s);

                for c in results {
                    let mut cols = Vec::with_capacity(columns.len());
                    let mut vals = Vec::with_capacity(c.len());

                    for (column_name, cap) in columns.iter().zip(c.iter().skip(1)) {
                        let cap_string = cap.map(|v| v.as_str()).unwrap_or("").to_string();
                        cols.push(column_name.clone());
                        vals.push(Value::String {
                            val: cap_string,
                            span: v.span()?,
                        });
                    }

                    parsed.push(Value::Record {
                        cols,
                        vals,
                        span: head,
                    });
                }
            }
            Err(_) => {
                return Err(ShellError::PipelineMismatch {
                    expected: Type::String,
                    expected_span: head,
                    origin: v.span()?,
                })
            }
        }
    }

    Ok(PipelineData::Stream(ValueStream::from_stream(
        parsed.into_iter(),
        None,
    )))
}

fn build_regex(input: &str, span: Span) -> Result<String, ShellError> {
    let mut output = "(?s)\\A".to_string();

    //let mut loop_input = input;
    let mut loop_input = input.chars().peekable();
    loop {
        let mut before = String::new();
        while let Some(c) = loop_input.next() {
            if c == '{' {
                // If '{{', still creating a plaintext parse command, but just for a single '{' char
                if loop_input.peek() == Some(&'{') {
                    let _ = loop_input.next();
                } else {
                    break;
                }
            }
            before.push(c);
        }

        if !before.is_empty() {
            output.push_str(&regex::escape(&before));
        }

        // Look for column as we're now at one
        let mut column = String::new();
        while let Some(c) = loop_input.next() {
            if c == '}' {
                break;
            }
            column.push(c);

            if loop_input.peek().is_none() {
                return Err(ShellError::DelimiterError(
                    "Found opening `{` without an associated closing `}`".to_owned(),
                    span,
                ));
            }
        }

        if !column.is_empty() {
            output.push_str("(?P<");
            output.push_str(&column);
            output.push_str(">.*?)");
        }

        if before.is_empty() && column.is_empty() {
            break;
        }
    }

    output.push_str("\\z");
    Ok(output)
}

fn column_names(regex: &Regex) -> Vec<String> {
    regex
        .capture_names()
        .enumerate()
        .skip(1)
        .map(|(i, name)| {
            name.map(String::from)
                .unwrap_or_else(|| format!("Capture{}", i))
        })
        .collect()
}

fn parse_regex_error(e: regex::Error, base_span: Span) -> ShellError {
    match e {
        regex::Error::Syntax(msg) => {
            let mut lines = msg.lines();

            let main_msg = lines
                .next()
                .map(|l| l.replace(':', ""))
                .expect("invalid regex pattern");

            let span = lines.nth(1).and_then(|l| l.find('^')).map(|space| {
                let start = base_span.start + space - 3;
                Span::new(start, start + 1)
            });

            let msg = lines
                .next()
                .and_then(|l| l.split(':').nth(1))
                .map(|s| format!("{}: {}", main_msg, s.trim()));

            match (msg, span) {
                (Some(msg), Some(span)) => ShellError::DelimiterError(msg, span),
                _ => ShellError::DelimiterError("Invalid regex".to_owned(), base_span),
            }
        }
        _ => ShellError::DelimiterError("Invalid regex".to_owned(), base_span),
    }
}

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

    #[test]
    fn test_examples() {
        crate::test_examples(Parse)
    }
}