// Copyright (C) 2022 Parity Technologies (UK) Ltd. (admin@parity.io)
// This file is a part of the scale-value crate.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//         http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use super::string_helpers;
use crate::value::{BitSequence, Composite, Primitive, Value, ValueDef, Variant};
use std::fmt::{Display, Write};

impl<T> Display for Value<T> {
	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
		self.value.fmt(f)
	}
}

impl<T> Display for ValueDef<T> {
	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
		match self {
			ValueDef::Composite(c) => c.fmt(f),
			ValueDef::Variant(v) => v.fmt(f),
			ValueDef::BitSequence(b) => fmt_bitsequence(b, f),
			ValueDef::Primitive(p) => p.fmt(f),
		}
	}
}

impl<T> Display for Composite<T> {
	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
		match self {
			Composite::Named(vals) => {
				f.write_str("{ ")?;
				for (idx, (name, val)) in vals.iter().enumerate() {
					if idx != 0 {
						f.write_str(", ")?;
					}
					if is_ident(name) {
						f.write_str(name)?;
					} else {
						fmt_string(name, f)?;
					}
					f.write_str(": ")?;
					val.fmt(f)?;
				}
				f.write_str(" }")?;
			}
			Composite::Unnamed(vals) => {
				f.write_char('(')?;
				for (idx, val) in vals.iter().enumerate() {
					if idx != 0 {
						f.write_str(", ")?;
					}
					val.fmt(f)?;
				}
				f.write_char(')')?;
			}
		}
		Ok(())
	}
}

impl<T> Display for Variant<T> {
	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
		if is_ident(&self.name) {
			f.write_str(&self.name)?;
		} else {
			// If the variant name isn't a valid ident, we parse it into
			// a special "v" prefixed string to allow arbitrary content while
			// keeping it easy to parse variant names with minimal lookahead.
			// Most use cases should never see or care about this.
			f.write_char('v')?;
			fmt_string(&self.name, f)?;
		}
		self.values.fmt(f)
	}
}

impl Display for Primitive {
	fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
		match self {
			Primitive::Bool(true) => f.write_str("true"),
			Primitive::Bool(false) => f.write_str("false"),
			Primitive::Char(c) => fmt_char(*c, f),
			Primitive::I128(n) => n.fmt(f),
			Primitive::U128(n) => n.fmt(f),
			Primitive::String(s) => fmt_string(s, f),
			// We don't currently have a sane way to parse into these or
			// format out of them:
			Primitive::U256(_) | Primitive::I256(_) => Err(std::fmt::Error),
		}
	}
}

fn fmt_string(s: &str, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
	f.write_char('"')?;
	for char in s.chars() {
		match string_helpers::to_escape_code(char) {
			Some(escaped) => {
				f.write_char('\\')?;
				f.write_char(escaped)?
			}
			None => f.write_char(char)?,
		}
	}
	f.write_char('"')
}

fn fmt_char(c: char, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
	f.write_char('\'')?;
	match string_helpers::to_escape_code(c) {
		Some(escaped) => {
			f.write_char('\\')?;
			f.write_char(escaped)?
		}
		None => f.write_char(c)?,
	}
	f.write_char('\'')
}

fn fmt_bitsequence(b: &BitSequence, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
	f.write_char('<')?;
	for bit in b.iter() {
		match bit {
			true => f.write_char('1')?,
			false => f.write_char('0')?,
		}
	}
	f.write_char('>')
}

/// Is the string provided a valid ident (as per from_string::parse_ident).
fn is_ident(s: &str) -> bool {
	for (idx, c) in s.chars().enumerate() {
		if (idx == 0 && !c.is_alphabetic()) || !c.is_alphanumeric() || c != '_' {
			return false;
		}
	}
	true
}

#[cfg(test)]
// These tests only work with from_string enabled, because we go back and forth from both.
#[cfg(feature = "from_string")]
mod test {
	use super::*;

	fn assert_from_to<T: std::fmt::Debug + PartialEq>(val: Value<T>) {
		let s = val.to_string();
		match crate::stringify::from_str(&s) {
			(Err(e), _) => {
				panic!("'{s}' cannot be parsed back into the value {val:?}: {e}");
			}
			(Ok(new_val), rest) => {
				assert_eq!(
					val.remove_context(),
					new_val,
					"value should be the same after parsing to/from a string"
				);
				assert_eq!(rest.len(), 0, "there should be no unparsed string but got '{rest}'");
			}
		}
	}

	#[test]
	fn primitives() {
		assert_from_to(Value::bool(true));
		assert_from_to(Value::bool(false));

		assert_from_to(Value::char('\n'));
		assert_from_to(Value::char('😀'));
		assert_from_to(Value::char('a'));
		assert_from_to(Value::char('\0'));
		assert_from_to(Value::char('\t'));

		assert_from_to(Value::i128(-123_456));
		assert_from_to(Value::u128(0));
		assert_from_to(Value::u128(123456));

		assert_from_to(Value::string("hello \"you\",\n\n\t How are you??"));
		assert_from_to(Value::string(""));
	}

	#[test]
	fn composites() {
		assert_from_to(Value::named_composite([
			("foo", Value::u128(12345)),
			("bar", Value::bool(true)),
			("a \"weird\" name", Value::string("Woop!")),
		]));
		assert_from_to(Value::unnamed_composite([
			Value::u128(12345),
			Value::bool(true),
			Value::string("Woop!"),
		]));
	}

	#[test]
	fn variants() {
		assert_from_to(Value::named_variant(
			"A weird variant name",
			[
				("foo", Value::u128(12345)),
				("bar", Value::bool(true)),
				("a \"weird\" name", Value::string("Woop!")),
			],
		));
		assert_from_to(Value::unnamed_variant(
			"MyVariant",
			[Value::u128(12345), Value::bool(true), Value::string("Woop!")],
		));
	}

	#[test]
	fn bit_sequences() {
		use scale_bits::bits;
		assert_from_to(Value::bit_sequence(bits![0, 1, 1, 0, 1, 1, 0]));
		assert_from_to(Value::bit_sequence(bits![]));
	}
}