130 lines
4.6 KiB
Go
130 lines
4.6 KiB
Go
// Mgmt
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// Copyright (C) James Shubin and the project contributors
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// Written by James Shubin <james@shubin.ca> and the project contributors
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <https://www.gnu.org/licenses/>.
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//
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// Additional permission under GNU GPL version 3 section 7
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//
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// If you modify this program, or any covered work, by linking or combining it
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// with embedded mcl code and modules (and that the embedded mcl code and
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// modules which link with this program, contain a copy of their source code in
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// the authoritative form) containing parts covered by the terms of any other
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// license, the licensors of this program grant you additional permission to
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// convey the resulting work. Furthermore, the licensors of this program grant
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// the original author, James Shubin, additional permission to update this
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// additional permission if he deems it necessary to achieve the goals of this
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// additional permission.
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package unification
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import (
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"context"
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"fmt"
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"github.com/purpleidea/mgmt/lang/interfaces"
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"github.com/purpleidea/mgmt/lang/types"
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"github.com/purpleidea/mgmt/util"
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)
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const (
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// ErrAmbiguous means we couldn't find a solution, but we weren't
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// inconsistent.
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ErrAmbiguous = util.Error("can't unify, no equalities were consumed, we're ambiguous")
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// StrategyNameKey is the string key used when choosing a solver name.
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StrategyNameKey = "name"
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// StrategyOptimizationsKey is the string key used to tell the solver
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// about the specific optimizations you'd like to request. The format
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// can be specific to each solver.
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StrategyOptimizationsKey = "optimizations"
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)
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// Init contains some handles that are used to initialize every solver. Each
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// individual solver can choose to omit using some of the fields.
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type Init struct {
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// Strategy is a hack to tune unification performance until we have an
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// overall cleaner unification algorithm in place.
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Strategy map[string]string
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// UnifiedState stores a common representation of our unification vars.
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UnifiedState *types.UnifiedState
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Debug bool
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Logf func(format string, v ...interface{})
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}
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// Data contains the input data for the solver to process.
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type Data struct {
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// UnificationInvariants is an alternate data representation for Solve.
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UnificationInvariants []*interfaces.UnificationInvariant
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}
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// Solver is the general interface that any solver needs to implement.
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type Solver interface {
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// Init initializes the solver struct before first use.
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Init(*Init) error
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// Solve performs the actual solving. It must return as soon as possible
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// if the context is closed.
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Solve(context.Context, *Data) (*InvariantSolution, error)
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}
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// registeredSolvers is a global map of all possible unification solvers which
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// can be used. You should never touch this map directly. Use methods like
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// Register instead.
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var registeredSolvers = make(map[string]func() Solver) // must initialize
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// Register takes a solver and its name and makes it available for use. It is
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// commonly called in the init() method of the solver at program startup. There
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// is no matching Unregister function.
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func Register(name string, solver func() Solver) {
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if _, exists := registeredSolvers[name]; exists {
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panic(fmt.Sprintf("a solver named %s is already registered", name))
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}
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//gob.Register(solver())
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registeredSolvers[name] = solver
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}
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// Lookup returns a pointer to the solver's struct.
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func Lookup(name string) (Solver, error) {
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solver, exists := registeredSolvers[name]
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if !exists {
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return nil, fmt.Errorf("not found")
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}
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return solver(), nil
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}
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// LookupDefault attempts to return a "default" solver.
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func LookupDefault() (Solver, error) {
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if len(registeredSolvers) == 0 {
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return nil, fmt.Errorf("no registered solvers")
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}
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if len(registeredSolvers) == 1 {
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for _, solver := range registeredSolvers {
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return solver(), nil // return the first and only one
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}
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}
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// TODO: Should we remove this empty string feature?
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// If one was registered with no name, then use that as the default.
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if solver, exists := registeredSolvers[""]; exists { // empty name
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return solver(), nil
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}
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return nil, fmt.Errorf("no registered default solver")
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}
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