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intersect.go
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intersect.go
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// Copyright 2017 Walter Schulze
//
// 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.
// Package intersect contains the implementation of the intersect plugin, which generates the deriveIntersect function.
// func deriveIntersect([]T, []T) []T
// func deriveIntersect(map[T]struct{}, map[T]struct{}) map[T]struct{}
//
// Example: https://github.com/awalterschulze/goderive/tree/master/example/plugin/intersect
package intersect
import (
"fmt"
"go/types"
"github.com/awalterschulze/goderive/derive"
)
// NewPlugin creates a new keys plugin.
// This function returns the plugin name, default prefix and a constructor for the intersect code generator.
func NewPlugin() derive.Plugin {
return derive.NewPlugin("intersect", "deriveIntersect", New)
}
// New is a constructor for the intersect code generator.
// This generator should be reconstructed for each package.
func New(typesMap derive.TypesMap, p derive.Printer, deps map[string]derive.Dependency) derive.Generator {
return &gen{
TypesMap: typesMap,
printer: p,
contains: deps["contains"],
min: deps["min"],
}
}
type gen struct {
derive.TypesMap
printer derive.Printer
contains derive.Dependency
min derive.Dependency
}
func (g *gen) Add(name string, typs []types.Type) (string, error) {
if len(typs) != 2 {
return "", fmt.Errorf("%s does not have two arguments", name)
}
if !types.Identical(typs[0], typs[1]) {
return "", fmt.Errorf("%s's two input types are not identical", name)
}
switch typ := typs[0].(type) {
case *types.Slice:
case *types.Map:
if !types.Identical(typ.Elem(), types.NewStruct(nil, nil)) {
return "", fmt.Errorf("%s takes an unsupported type: %s, map must be of type map[T]struct{}", name, typ)
}
default:
return "", fmt.Errorf("%s takes an unsupported type: %s", name, typ)
}
return g.SetFuncName(name, typs[0])
}
func (g *gen) Generate(typs []types.Type) error {
switch typ := typs[0].(type) {
case *types.Slice:
return g.genSlice(typ)
case *types.Map:
return g.genMap(typ)
}
return fmt.Errorf("%s, the argument type, %s, is not of type slice or map[T]struct{}", g.GetFuncName(typs[0]), typs[0])
}
func (g *gen) genMap(typ *types.Map) error {
p := g.printer
g.Generating(typ)
name := g.GetFuncName(typ)
typeStr := g.TypeString(typ.Key())
p.P("")
p.P("// %s returns the intersection of the two maps' keys.", name)
p.P("func %s(this, that map[%s]struct{}) map[%s]struct{} {", name, typeStr, typeStr)
p.In()
minFunc := g.min.GetFuncName(types.Typ[types.Int], types.Typ[types.Int])
p.P("intersect := make(map[%s]struct{}, %s(len(this), len(that)))", typeStr, minFunc)
p.P("for k := range this {")
p.In()
p.P("if _, ok := that[k]; ok {")
p.In()
p.P("intersect[k] = struct{}{}")
p.Out()
p.P("}")
p.Out()
p.P("}")
p.P("return intersect")
p.Out()
p.P("}")
return nil
}
func (g *gen) genSlice(typ *types.Slice) error {
p := g.printer
g.Generating(typ)
name := g.GetFuncName(typ)
typeStr := g.TypeString(typ.Elem())
p.P("")
p.P("// %s returns the intersection of the two lists' values", name)
p.P("// It assumes that the first list only contains unique items.")
p.P("func %s(this, that []%s) []%s {", name, typeStr, typeStr)
p.In()
minFunc := g.min.GetFuncName(types.Typ[types.Int], types.Typ[types.Int])
p.P("intersect := make([]%s, 0, %s(len(this), len(that)))", typeStr, minFunc)
p.P("for i, v := range this {")
p.In()
p.P("if %s(that, v) {", g.contains.GetFuncName(typ))
p.In()
p.P("intersect = append(intersect, this[i])")
p.Out()
p.P("}")
p.Out()
p.P("}")
p.P("return intersect")
p.Out()
p.P("}")
return nil
}