// Copyright 2021 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// Package summarize produces a FIDL API summary from FIDL IR.
package summarize

import (
	"encoding/json"
	"io"
	"sort"

	"go.fuchsia.dev/fuchsia/tools/fidl/lib/fidlgen"
)

type summary []element

// IsEmptyLibrary returns true if the summary contains only an empty library.
func (s summary) IsEmptyLibrary() bool {
	if len(s) != 1 {
		return false
	}
	_, isLibrary := s[0].(*library)
	return isLibrary
}

// WriteJSON writes out the summary as JSON.
func (s summary) WriteJSON(w io.Writer) error {
	e := json.NewEncoder(w)
	// 4-level indent is chosen to match `fx format-code`.
	e.SetIndent("", "    ")
	e.SetEscapeHTML(false)
	return e.Encode(serialize([]element(s)))
}

// element describes a single platform surface element.
type element interface {
	// Member returns true if the Element is a member of something.
	Member() bool
	// Name returns the fully-qualified name of this Element.  For example,
	// "library/protocol.Method".
	Name() Name
	// Serialize converts an Element into a serializable representation.
	Serialize() ElementStr
}

var _ = []element{
	(*aConst)(nil),
	(*aggregate)(nil),
	(*alias)(nil),
	(*bits)(nil),
	(*enum)(nil),
	(*library)(nil),
	(*member)(nil),
	(*method)(nil),
	(*protocol)(nil),
}

type summarizer struct {
	elements elementSlice
	symbols  symbolTable
}

// addElement adds an element for summarization.
func (s *summarizer) addElement(e element) {
	s.elements = append(s.elements, e)
}

// addUnions adds the elements corresponding to the FIDL unions.
func (s *summarizer) addUnions(unions []fidlgen.Union) {
	for _, st := range unions {
		for _, m := range st.Members {
			s.addElement(newMember(
				&s.symbols, st.Name, m.Name, m.Type, fidlgen.UnionDeclType, m.Ordinal, nil))
		}
		s.addElement(
			newAggregateWithStrictness(
				st.Name, st.Resourceness, fidlgen.UnionDeclType, st.Strictness))
	}
}

// addTables adds the elements corresponding to the FIDL tables.
func (s *summarizer) addTables(tables []fidlgen.Table) {
	for _, st := range tables {
		for _, m := range st.Members {
			s.addElement(newMember(&s.symbols, st.Name, m.Name, m.Type, fidlgen.TableDeclType, m.Ordinal, nil))
		}
		s.addElement(newAggregate(st.Name, st.Resourceness, fidlgen.TableDeclType))
	}
}

// addStructs adds the elements corresponding to the FIDL structs.
func (s *summarizer) addStructs(structs []fidlgen.Struct) {
	for _, st := range structs {
		for idx, m := range st.Members {
			oneBased := idx + 1
			s.addElement(newMember(
				&s.symbols, st.Name, m.Name, m.Type, fidlgen.StructDeclType, oneBased, m.MaybeDefaultValue))
		}
		s.addElement(newAggregate(st.Name, st.Resourceness, fidlgen.StructDeclType))
	}
}

// registerStructs registers names of all the structs in the FIDL IR.
func (s *summarizer) registerStructs(structs []fidlgen.Struct) {
	for _, st := range structs {
		st := st
		s.symbols.addStruct(st.Name, &st)
	}
}

func serialize(e []element) []ElementStr {
	var ret []ElementStr
	for _, l := range e {
		ret = append(ret, l.Serialize())
	}
	return ret
}

// filterStructs filters out structs that should not be included in API summaries.
func filterStructs(structs []fidlgen.Struct) []fidlgen.Struct {
	var out []fidlgen.Struct
	for _, s := range structs {
		if s.IsEmptySuccessStruct {
			continue
		}
		out = append(out, s)
	}
	return out
}

// filterUnions filters out unions that should not be included in API summaries.
func filterUnions(unions []fidlgen.Union) []fidlgen.Union {
	var out []fidlgen.Union
	for _, u := range unions {
		if u.IsResult {
			continue
		}
		out = append(out, u)
	}
	return out
}

// Summarize converts FIDL IR to an API summary.
func Summarize(root fidlgen.Root) summary {
	var s summarizer

	s.registerStructs(root.Structs)
	s.registerStructs(root.ExternalStructs)
	s.registerProtocolNames(root.Protocols)

	s.addConsts(root.Consts)
	s.addBits(root.Bits)
	s.addEnums(root.Enums)
	s.addStructs(filterStructs(root.Structs))
	s.addTables(root.Tables)
	s.addUnions(filterUnions(root.Unions))
	s.addProtocols(root.Protocols)
	s.addElement(&library{r: root})

	// TODO(https://fxbug.dev/42158155): Add aliases.

	sort.Sort(s.elements)
	return summary(s.elements)
}