use crate::registry::{MetaField, MetaInputValue, MetaType, Registry};
use itertools::Itertools;
use std::fmt::Write;

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.args.is_empty() {
                write!(
                    sdl,
                    "\t{}({}): {}",
                    field.name,
                    field
                        .args
                        .values()
                        .map(|arg| export_input_value(arg))
                        .join(", "),
                    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, .. } => {
                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 {
                    writeln!(sdl, "scalar {}", name).ok();
                }
            }
            MetaType::Object {
                name,
                fields,
                extends,
                keys,
                ..
            } => {
                if name == &self.query_type && self.is_empty_query {
                    return;
                }

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

                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 {} ", implements.iter().join(" & ")).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,
                ..
            } => {
                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, ..
            } => {
                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, ..
            } => {
                write!(sdl, "input {} ", name).ok();
                writeln!(sdl, "{{").ok();
                for field in input_fields.values() {
                    writeln!(sdl, "{}", export_input_value(&field)).ok();
                }
                writeln!(sdl, "}}").ok();
            }
            MetaType::Union {
                name,
                possible_types,
                ..
            } => {
                writeln!(
                    sdl,
                    "union {} = {}",
                    name,
                    possible_types.iter().join(" | ")
                )
                .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)
    }
}