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use std::collections::HashMap;

use crate::interpolate::*;
use crate::text::*;

pub fn brace(s: &str, named: &HashMap<String, String>, positional: &Vec<String>,
             default_value: Option<&str>) -> Result<String, InterpolationError>{
    let size = s.len();
    if size <= 1 {
        return Ok(s.to_string())
    }

    let mut result = String::with_capacity(size_grow_up(size));
    let mut enter_brace = false; // in case like {...}
    let mut enter_positional = false; // in case like {1}
    let mut left_index = 0;
    let mut colon_index = 0; // the index of char `:`
    let mut k = -1;
    let mut default_index = 0;
    loop {
        k += 1;
        let mut i = k as usize;
        if i >= size { break }
        let c = s.get(i..(i+1)).ok_or(unexpected_err(s, i, "s.get(i..(i+1))"))?
            .chars().next().ok_or(unexpected_err(s, i, "chars().next()"))?;
        if enter_brace {
            if c == '\\' {
                if i == size - 1 {
                    return Err(invalid_char_err(c, i))
                }
                k += 1;
                continue
            }
            if c == ':' && colon_index == 0 {
                colon_index = i;
                continue
            }
            if c != '}' { continue }
            // extract xxx from ${xxx}
            let right_index = if colon_index != 0 { colon_index } else { i };
            let variable = s.get(left_index..right_index).unwrap();
            // remove escape character
            let variable = from_backslash(variable);
            if let Some(value) = named.get(&variable) {
                result.push_str(value);
            } else {
                // has no default value
                if colon_index == 0 {
                    add_default_value(&mut result, default_value, variable)?;
                } else {
                    // extract ### from ${@@@:###}
                    let value = s.get((colon_index + 1)..i).unwrap();
                    let value = from_backslash(value);
                    result.push_str(&value);
                }
            }
            enter_brace = false;
            colon_index = 0;
            continue
        }
        if enter_positional {
            if is_number_char(c) { continue }
            if c != '}' {
                return Err(invalid_char_err(c, i))
            }
            let variable = s.get(left_index..i).unwrap();
            let n = variable.parse::<usize>().map_err(
                |e| number_parse_err(left_index, variable.to_string(), e.to_string()))?;
            if let Some(argument) = positional.get(n) {
                result.push_str(argument);
            } else {
                add_default_value(&mut result, default_value, variable.to_string())?;
            }
            enter_positional = false;
            continue
        }
        if i == size - 1 {
            result.push(c);
            break
        }
        // escape char
        if c == '\\' {
            k += 1;
            i = k as usize;
            let next = s.get(i..(i+1)).unwrap().chars().next().unwrap();
            result.push(next);
            continue;
        }
        if c != '{' {
            result.push(c);
            continue
        }
        // then c is {
        k += 1;
        i = k as usize;
        let next = s.get(i..(i+1)).unwrap().chars().next().unwrap();
        if next == '}' {
            if let Some(argument) = positional.get(default_index) {
                result.push_str(argument);
            } else {
                add_default_value_positional(&mut result, default_value, default_index)?;
            }
            default_index += 1;
            continue
        }
        if is_number_char(next) {
            left_index = i;
            enter_positional = true;
            continue
        }
        if is_first_variable_char(next) {
            left_index = i;
            enter_brace = true;
            continue
        }
        return Err(invalid_char_err(next, i))
    }
    Ok(result)
}

pub fn brace_named(s: &str, named: &HashMap<String, String>, default_value: Option<&str>)
    -> Result<String, InterpolationError>{
    brace(s, named, &Vec::new(), default_value)
}

pub fn brace_positional(s: &str, positional: &Vec<String>, default_value: Option<&str>)
    -> Result<String, InterpolationError>{
    brace(s, &HashMap::new(), positional, default_value)
}

pub fn brace_unwrap(s: &str, positional: Vec<String>) -> String {
    brace_positional(s, &positional, None).unwrap()
}