use std::str::FromStr;

use toml_datetime::Datetime;

use crate::array_of_tables::ArrayOfTables;
use crate::table::TableLike;
use crate::{Array, InlineTable, Table, Value};

/// Type representing either a value, a table, an array of tables, or none.
#[derive(Debug, Default)]
pub enum Item {
    /// Type representing none.
    #[default]
    None,
    /// Type representing value.
    Value(Value),
    /// Type representing table.
    Table(Table),
    /// Type representing array of tables.
    ArrayOfTables(ArrayOfTables),
}

impl Item {
    /// Sets `self` to the given item if `self` is none and
    /// returns a mutable reference to `self`.
    pub fn or_insert(&mut self, item: Item) -> &mut Item {
        if self.is_none() {
            *self = item;
        }
        self
    }
}

// TODO: This should be generated by macro or derive
/// Downcasting
impl Item {
    /// Text description of value type
    pub fn type_name(&self) -> &'static str {
        match self {
            Item::None => "none",
            Item::Value(v) => v.type_name(),
            Item::Table(..) => "table",
            Item::ArrayOfTables(..) => "array of tables",
        }
    }

    /// Index into a TOML array or map. A string index can be used to access a
    /// value in a map, and a usize index can be used to access an element of an
    /// array.
    ///
    /// Returns `None` if:
    /// - The type of `self` does not match the type of the
    ///   index, for example if the index is a string and `self` is an array or a
    ///   number.
    /// - The given key does not exist in the map
    ///   or the given index is not within the bounds of the array.
    pub fn get<I: crate::index::Index>(&self, index: I) -> Option<&Item> {
        index.index(self)
    }

    /// Mutably index into a TOML array or map. A string index can be used to
    /// access a value in a map, and a usize index can be used to access an
    /// element of an array.
    ///
    /// Returns `None` if:
    /// - The type of `self` does not match the type of the
    ///   index, for example if the index is a string and `self` is an array or a
    ///   number.
    /// - The given key does not exist in the map
    ///   or the given index is not within the bounds of the array.
    pub fn get_mut<I: crate::index::Index>(&mut self, index: I) -> Option<&mut Item> {
        index.index_mut(self)
    }

    /// Casts `self` to value.
    pub fn as_value(&self) -> Option<&Value> {
        match *self {
            Item::Value(ref v) => Some(v),
            _ => None,
        }
    }
    /// Casts `self` to table.
    pub fn as_table(&self) -> Option<&Table> {
        match *self {
            Item::Table(ref t) => Some(t),
            _ => None,
        }
    }
    /// Casts `self` to array of tables.
    pub fn as_array_of_tables(&self) -> Option<&ArrayOfTables> {
        match *self {
            Item::ArrayOfTables(ref a) => Some(a),
            _ => None,
        }
    }
    /// Casts `self` to mutable value.
    pub fn as_value_mut(&mut self) -> Option<&mut Value> {
        match *self {
            Item::Value(ref mut v) => Some(v),
            _ => None,
        }
    }
    /// Casts `self` to mutable table.
    pub fn as_table_mut(&mut self) -> Option<&mut Table> {
        match *self {
            Item::Table(ref mut t) => Some(t),
            _ => None,
        }
    }
    /// Casts `self` to mutable array of tables.
    pub fn as_array_of_tables_mut(&mut self) -> Option<&mut ArrayOfTables> {
        match *self {
            Item::ArrayOfTables(ref mut a) => Some(a),
            _ => None,
        }
    }
    /// Casts `self` to value.
    pub fn into_value(self) -> Result<Value, Self> {
        match self {
            Item::None => Err(self),
            Item::Value(v) => Ok(v),
            Item::Table(v) => {
                let v = v.into_inline_table();
                Ok(Value::InlineTable(v))
            }
            Item::ArrayOfTables(v) => {
                let v = v.into_array();
                Ok(Value::Array(v))
            }
        }
    }
    /// In-place convert to a value
    pub fn make_value(&mut self) {
        let other = std::mem::take(self);
        let other = other.into_value().map(Item::Value).unwrap_or(Item::None);
        *self = other;
    }
    /// Casts `self` to table.
    pub fn into_table(self) -> Result<Table, Self> {
        match self {
            Item::Table(t) => Ok(t),
            Item::Value(Value::InlineTable(t)) => Ok(t.into_table()),
            _ => Err(self),
        }
    }
    /// Casts `self` to array of tables.
    pub fn into_array_of_tables(self) -> Result<ArrayOfTables, Self> {
        match self {
            Item::ArrayOfTables(a) => Ok(a),
            Item::Value(Value::Array(a)) => {
                if a.is_empty() {
                    Err(Item::Value(Value::Array(a)))
                } else if a.iter().all(|v| v.is_inline_table()) {
                    let mut aot = ArrayOfTables::new();
                    aot.values = a.values;
                    for value in aot.values.iter_mut() {
                        value.make_item();
                    }
                    Ok(aot)
                } else {
                    Err(Item::Value(Value::Array(a)))
                }
            }
            _ => Err(self),
        }
    }
    // Starting private because the name is unclear
    pub(crate) fn make_item(&mut self) {
        let other = std::mem::take(self);
        let other = match other.into_table().map(Item::Table) {
            Ok(i) => i,
            Err(i) => i,
        };
        let other = match other.into_array_of_tables().map(Item::ArrayOfTables) {
            Ok(i) => i,
            Err(i) => i,
        };
        *self = other;
    }
    /// Returns true if `self` is a value.
    pub fn is_value(&self) -> bool {
        self.as_value().is_some()
    }
    /// Returns true if `self` is a table.
    pub fn is_table(&self) -> bool {
        self.as_table().is_some()
    }
    /// Returns true if `self` is an array of tables.
    pub fn is_array_of_tables(&self) -> bool {
        self.as_array_of_tables().is_some()
    }
    /// Returns true if `self` is `None`.
    pub fn is_none(&self) -> bool {
        matches!(*self, Item::None)
    }

    // Duplicate Value downcasting API

    /// Casts `self` to integer.
    pub fn as_integer(&self) -> Option<i64> {
        self.as_value().and_then(Value::as_integer)
    }

    /// Returns true if `self` is an integer.
    pub fn is_integer(&self) -> bool {
        self.as_integer().is_some()
    }

    /// Casts `self` to float.
    pub fn as_float(&self) -> Option<f64> {
        self.as_value().and_then(Value::as_float)
    }

    /// Returns true if `self` is a float.
    pub fn is_float(&self) -> bool {
        self.as_float().is_some()
    }

    /// Casts `self` to boolean.
    pub fn as_bool(&self) -> Option<bool> {
        self.as_value().and_then(Value::as_bool)
    }

    /// Returns true if `self` is a boolean.
    pub fn is_bool(&self) -> bool {
        self.as_bool().is_some()
    }

    /// Casts `self` to str.
    pub fn as_str(&self) -> Option<&str> {
        self.as_value().and_then(Value::as_str)
    }

    /// Returns true if `self` is a string.
    pub fn is_str(&self) -> bool {
        self.as_str().is_some()
    }

    /// Casts `self` to date-time.
    pub fn as_datetime(&self) -> Option<&Datetime> {
        self.as_value().and_then(Value::as_datetime)
    }

    /// Returns true if `self` is a date-time.
    pub fn is_datetime(&self) -> bool {
        self.as_datetime().is_some()
    }

    /// Casts `self` to array.
    pub fn as_array(&self) -> Option<&Array> {
        self.as_value().and_then(Value::as_array)
    }

    /// Casts `self` to mutable array.
    pub fn as_array_mut(&mut self) -> Option<&mut Array> {
        self.as_value_mut().and_then(Value::as_array_mut)
    }

    /// Returns true if `self` is an array.
    pub fn is_array(&self) -> bool {
        self.as_array().is_some()
    }

    /// Casts `self` to inline table.
    pub fn as_inline_table(&self) -> Option<&InlineTable> {
        self.as_value().and_then(Value::as_inline_table)
    }

    /// Casts `self` to mutable inline table.
    pub fn as_inline_table_mut(&mut self) -> Option<&mut InlineTable> {
        self.as_value_mut().and_then(Value::as_inline_table_mut)
    }

    /// Returns true if `self` is an inline table.
    pub fn is_inline_table(&self) -> bool {
        self.as_inline_table().is_some()
    }

    /// Casts `self` to either a table or an inline table.
    pub fn as_table_like(&self) -> Option<&dyn TableLike> {
        self.as_table()
            .map(|t| t as &dyn TableLike)
            .or_else(|| self.as_inline_table().map(|t| t as &dyn TableLike))
    }

    /// Casts `self` to either a table or an inline table.
    pub fn as_table_like_mut(&mut self) -> Option<&mut dyn TableLike> {
        match self {
            Item::Table(t) => Some(t as &mut dyn TableLike),
            Item::Value(Value::InlineTable(t)) => Some(t as &mut dyn TableLike),
            _ => None,
        }
    }

    /// Returns true if `self` is either a table, or an inline table.
    pub fn is_table_like(&self) -> bool {
        self.as_table_like().is_some()
    }

    /// The location within the original document
    ///
    /// This generally requires an [`ImDocument`][crate::ImDocument].
    pub fn span(&self) -> Option<std::ops::Range<usize>> {
        match self {
            Item::None => None,
            Item::Value(v) => v.span(),
            Item::Table(v) => v.span(),
            Item::ArrayOfTables(v) => v.span(),
        }
    }

    pub(crate) fn despan(&mut self, input: &str) {
        match self {
            Item::None => {}
            Item::Value(v) => v.despan(input),
            Item::Table(v) => v.despan(input),
            Item::ArrayOfTables(v) => v.despan(input),
        }
    }
}

impl Clone for Item {
    #[inline(never)]
    fn clone(&self) -> Self {
        match self {
            Item::None => Item::None,
            Item::Value(v) => Item::Value(v.clone()),
            Item::Table(v) => Item::Table(v.clone()),
            Item::ArrayOfTables(v) => Item::ArrayOfTables(v.clone()),
        }
    }
}

#[cfg(feature = "parse")]
impl FromStr for Item {
    type Err = crate::TomlError;

    /// Parses a value from a &str
    fn from_str(s: &str) -> Result<Self, Self::Err> {
        let value = s.parse::<Value>()?;
        Ok(Item::Value(value))
    }
}

#[cfg(feature = "display")]
impl std::fmt::Display for Item {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match &self {
            Item::None => Ok(()),
            Item::Value(v) => v.fmt(f),
            Item::Table(v) => v.fmt(f),
            Item::ArrayOfTables(v) => v.fmt(f),
        }
    }
}

/// Returns a formatted value.
///
/// Since formatting is part of a `Value`, the right hand side of the
/// assignment needs to be decorated with a space before the value.
/// The `value` function does just that.
///
/// # Examples
/// ```rust
/// # #[cfg(feature = "display")] {
/// # #[cfg(feature = "parse")] {
/// # use snapbox::assert_eq;
/// # use toml_edit::*;
/// let mut table = Table::default();
/// let mut array = Array::default();
/// array.push("hello");
/// array.push("\\, world"); // \ is only allowed in a literal string
/// table["key1"] = value("value1");
/// table["key2"] = value(42);
/// table["key3"] = value(array);
/// assert_eq(table.to_string(),
/// r#"key1 = "value1"
/// key2 = 42
/// key3 = ["hello", '\, world']
/// "#);
/// # }
/// # }
/// ```
pub fn value<V: Into<Value>>(v: V) -> Item {
    Item::Value(v.into())
}

/// Returns an empty table.
pub fn table() -> Item {
    Item::Table(Table::new())
}

/// Returns an empty array of tables.
pub fn array() -> Item {
    Item::ArrayOfTables(ArrayOfTables::new())
}

#[test]
#[cfg(feature = "parse")]
#[cfg(feature = "display")]
fn string_roundtrip() {
    value("hello").to_string().parse::<Item>().unwrap();
}