use std::fmt::Write;

use crate::registry::{MetaField, MetaInputValue, MetaType, Registry};

impl Registry {
    pub fn export_sdl(&self, federation: bool) -> String {
        let mut sdl = String::new();

        for ty in self.types.values() {
            if ty.name().starts_with("__") {
                continue;
            }

            if federation {
                const FEDERATION_TYPES: &[&str] = &["_Any", "_Entity", "_Service"];
                if FEDERATION_TYPES.contains(&ty.name()) {
                    continue;
                }
            }

            self.export_type(ty, &mut sdl, federation);
        }

        if !federation {
            writeln!(sdl, "schema {{").ok();
            writeln!(sdl, "\tquery: {}", self.query_type).ok();
            if let Some(mutation_type) = self.mutation_type.as_deref() {
                writeln!(sdl, "\tmutation: {}", mutation_type).ok();
            }
            if let Some(subscription_type) = self.subscription_type.as_deref() {
                writeln!(sdl, "\tsubscription: {}", subscription_type).ok();
            }
            writeln!(sdl, "}}").ok();
        }

        sdl
    }

    fn export_fields<'a, I: Iterator<Item = &'a MetaField>>(
        sdl: &mut String,
        it: I,
        federation: bool,
    ) {
        for field in it {
            if field.name.starts_with("__")
                || (federation && matches!(&*field.name, "_service" | "_entities"))
            {
                continue;
            }

            if field.description.is_some() && !federation {
                writeln!(
                    sdl,
                    "\t\"\"\"\n\t{}\n\t\"\"\"",
                    field.description.unwrap().replace("\n", "\n\t")
                )
                .ok();
            }
            if !field.args.is_empty() {
                write!(sdl, "\t{}(", field.name).ok();
                for (i, arg) in field.args.values().enumerate() {
                    if i != 0 {
                        sdl.push_str(", ");
                    }
                    sdl.push_str(&export_input_value(arg));
                }
                write!(sdl, "): {}", field.ty).ok();
            } else {
                write!(sdl, "\t{}: {}", field.name, field.ty).ok();
            }

            if federation {
                if field.external {
                    write!(sdl, " @external").ok();
                }
                if let Some(requires) = field.requires {
                    write!(sdl, " @requires(fields: \"{}\")", requires).ok();
                }
                if let Some(provides) = field.provides {
                    write!(sdl, " @provides(fields: \"{}\")", provides).ok();
                }
            }

            writeln!(sdl).ok();
        }
    }

    fn export_type(&self, ty: &MetaType, sdl: &mut String, federation: bool) {
        match ty {
            MetaType::Scalar {
                name, description, ..
            } => {
                const SYSTEM_SCALARS: &[&str] = &["Int", "Float", "String", "Boolean", "ID"];
                const FEDERATION_SCALARS: &[&str] = &["Any"];
                let mut export_scalar = !SYSTEM_SCALARS.contains(&name.as_str());
                if federation && FEDERATION_SCALARS.contains(&name.as_str()) {
                    export_scalar = false;
                }
                if export_scalar {
                    if description.is_some() && !federation {
                        writeln!(sdl, "\"\"\"\n{}\n\"\"\"", description.unwrap()).ok();
                    }
                    writeln!(sdl, "scalar {}", name).ok();
                }
            }
            MetaType::Object {
                name,
                fields,
                extends,
                keys,
                description,
                ..
            } => {
                if name == &self.query_type && federation && fields.len() <= 4 {
                    // Is empty query root, only __schema, __type, _service, _entities fields
                    return;
                }

                if let Some(subscription_type) = &self.subscription_type {
                    if name == subscription_type && federation {
                        return;
                    }
                }

                if description.is_some() && !federation {
                    writeln!(sdl, "\"\"\"\n{}\n\"\"\"", description.unwrap()).ok();
                }
                if federation && *extends {
                    write!(sdl, "extend ").ok();
                }
                write!(sdl, "type {} ", name).ok();
                if let Some(implements) = self.implements.get(name) {
                    if !implements.is_empty() {
                        write!(sdl, "implements ").ok();
                        for interface in implements {
                            write!(sdl, "& {} ", interface).ok();
                        }
                    }
                }

                if federation {
                    if let Some(keys) = keys {
                        for key in keys {
                            write!(sdl, "@key(fields: \"{}\") ", key).ok();
                        }
                    }
                }

                writeln!(sdl, "{{").ok();
                Self::export_fields(sdl, fields.values(), federation);
                writeln!(sdl, "}}").ok();
            }
            MetaType::Interface {
                name,
                fields,
                extends,
                keys,
                description,
                ..
            } => {
                if description.is_some() && !federation {
                    writeln!(sdl, "\"\"\"\n{}\n\"\"\"", description.unwrap()).ok();
                }
                if federation && *extends {
                    write!(sdl, "extend ").ok();
                }
                write!(sdl, "interface {} ", name).ok();
                if federation {
                    if let Some(keys) = keys {
                        for key in keys {
                            write!(sdl, "@key(fields: \"{}\") ", key).ok();
                        }
                    }
                }
                writeln!(sdl, "{{").ok();
                Self::export_fields(sdl, fields.values(), federation);
                writeln!(sdl, "}}").ok();
            }
            MetaType::Enum {
                name,
                enum_values,
                description,
                ..
            } => {
                if description.is_some() && !federation {
                    writeln!(sdl, "\"\"\"\n{}\n\"\"\"", description.unwrap()).ok();
                }
                write!(sdl, "enum {} ", name).ok();
                writeln!(sdl, "{{").ok();
                for value in enum_values.values() {
                    writeln!(sdl, "\t{}", value.name).ok();
                }
                writeln!(sdl, "}}").ok();
            }
            MetaType::InputObject {
                name,
                input_fields,
                description,
                ..
            } => {
                if description.is_some() && !federation {
                    writeln!(sdl, "\"\"\"\n{}\n\"\"\"", description.unwrap()).ok();
                }
                write!(sdl, "input {} ", name).ok();
                writeln!(sdl, "{{").ok();
                for field in input_fields.values() {
                    if let Some(description) = field.description {
                        writeln!(sdl, "\"\"\"\n{}\n\"\"\"", description).ok();
                    }
                    writeln!(sdl, "{}", export_input_value(&field)).ok();
                }
                writeln!(sdl, "}}").ok();
            }
            MetaType::Union {
                name,
                possible_types,
                description,
                ..
            } => {
                if description.is_some() && !federation {
                    writeln!(sdl, "\"\"\"\n{}\n\"\"\"", description.unwrap()).ok();
                }
                write!(sdl, "union {} =", name).ok();
                for ty in possible_types {
                    write!(sdl, " | {}", ty).ok();
                }
                writeln!(sdl).ok();
            }
        }
    }
}

fn export_input_value(input_value: &MetaInputValue) -> String {
    if let Some(default_value) = &input_value.default_value {
        format!(
            "{}: {} = {}",
            input_value.name, input_value.ty, default_value
        )
    } else {
        format!("{}: {}", input_value.name, input_value.ty)
    }
}