use crate::prelude::*;
use nu_engine::WholeStreamCommand;
use nu_errors::ShellError;
use nu_protocol::{Signature, SyntaxShape, TaggedDictBuilder, UntaggedValue, Value};
use nu_source::Tagged;

use regex::{self, Regex};

pub struct Command;

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

    fn signature(&self) -> 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'))
    }

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

    fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
        operate(args)
    }

    fn examples(&self) -> Vec<Example> {
        let mut row = IndexMap::new();
        row.insert("foo".to_string(), Value::from("hi"));
        row.insert("bar".to_string(), Value::from("there"));
        vec![
            Example {
                description: "Parse a string into two named columns",
                example: "echo \"hi there\" | parse \"{foo} {bar}\"",
                result: Some(vec![UntaggedValue::row(row.clone()).into()]),
            },
            Example {
                description: "Parse a string using regex pattern",
                example: "echo \"hi there\" | parse -r \"(?P<foo>\\w+) (?P<bar>\\w+)\"",
                result: Some(vec![UntaggedValue::row(row).into()]),
            },
        ]
    }
}

pub fn operate(args: CommandArgs) -> Result<OutputStream, ShellError> {
    let name_tag = args.call_info.name_tag.clone();

    let pattern: Tagged<String> = args.req(0)?;
    let regex: bool = args.has_flag("regex");

    let item_to_parse = if regex {
        pattern.item.clone()
    } else {
        build_regex(&pattern.item, pattern.tag.clone())?
    };

    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: VecDeque<Value> = VecDeque::new();

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

                for c in results {
                    let mut dict = TaggedDictBuilder::new(&v.tag);

                    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();
                        dict.insert_untagged(column_name, UntaggedValue::string(cap_string));
                    }

                    parsed.push_back(dict.into_value());
                }
            }
            Err(_) => {
                return Err(ShellError::labeled_error_with_secondary(
                    "Expected string input",
                    "expected string input",
                    &name_tag,
                    "value originated here",
                    v.tag,
                ))
            }
        }
    }

    Ok(parsed.into_iter().into_output_stream())
}

fn build_regex(input: &str, tag: Tag) -> 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::labeled_error(
                    "Found opening `{` without an associated closing `}`",
                    "invalid parse pattern",
                    tag,
                ));
            }
        }

        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).map(|l| l.find('^')).flatten().map(|space| {
                let start = base_span.start() + space - 3;
                Span::for_char(start)
            });

            let msg = lines
                .next()
                .map(|l| l.split(':').nth(1))
                .flatten()
                .map(|s| s.trim().to_string());

            match (msg, span) {
                (Some(msg), Some(span)) => {
                    ShellError::labeled_error_with_secondary(&msg, &msg, span, main_msg, span)
                }
                _ => ShellError::labeled_error("Invalid regex", "invalid regex", base_span),
            }
        }
        _ => ShellError::labeled_error("Invalid regex", "invalid regex", base_span),
    }
}

#[cfg(test)]
mod tests {
    use super::Command;
    use super::ShellError;

    #[test]
    fn examples_work_as_expected() -> Result<(), ShellError> {
        use crate::examples::test as test_examples;

        test_examples(Command {})
    }
}