// Copyright 2022 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 util

import (
	"encoding/json"
	"fmt"
	"os"
	"regexp"
	"strings"
)

type Gen struct {
	Targets   map[string]*Target `json:"targets"`
	IsCleaned bool               `json:"cleaned"`

	re *regexp.Regexp `json:"-"`
}

func LoadGen(path string) (*Gen, error) {
	b, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("Failed to read [%s] gen file: %w\n", path, err)
	}

	gen := Gen{
		Targets: make(map[string]*Target),

		// Many rust_crate projects have a suffix in the label name that
		// doesn't map to a directory. We use a regular expression to
		// strip that part of the label text away. We store the regexp
		// in this GN struct so we don't have to recompile the regex on
		// each loop.
		re: regexp.MustCompile(`(.*)-v(\d+)_(\d+)_(\d+)(.*)`),
	}
	d := json.NewDecoder(strings.NewReader(string(b)))
	if err := d.Decode(&gen); err != nil {
		return nil, fmt.Errorf("Failed to decode [%s] into struct object: %w", path, err)
	}
	return &gen, nil
}
func (g *Gen) clean() error {
	if g.IsCleaned {
		return fmt.Errorf("gen file is already cleaned.")
	}

	toAdd := make(map[string]*Target, 0)
	for name, t := range g.Targets {
		t.Name = name
		if err := t.Clean(g.re); err != nil {
			return fmt.Errorf("Failed to clean target %v: %w", t, err)
		}
		for _, n := range t.CleanNames {
			toAdd[n] = t
		}
	}

	for k, v := range toAdd {
		if _, ok := g.Targets[k]; !ok {
			g.Targets[k] = v
		}
	}

	g.IsCleaned = true
	return nil
}

func (g *Gen) FilterTargetsInDependencyTree(rootTarget string, excludeTargets map[string]bool) error {
	g.clean()

	root := g.Targets[rootTarget]
	if root == nil {
		return fmt.Errorf("Failed to find %v target in the Gen target map", rootTarget)
	}

	toProcess := []*Target{root}
	seenTargets := make(map[string]*Target)

	for len(toProcess) > 0 {
		toProcessNext := []*Target{}

	OUTER:
		for _, t := range toProcess {

			// If this target matches any entry in our excludeTargets map,
			// skip processing this target.
			for _, cleanName := range t.CleanNames {
				if _, ok := excludeTargets[cleanName]; ok {
					continue OUTER
				}
			}
			for _, cleanName := range t.CleanNames {
				seenTargets[cleanName] = t
			}

			for _, d := range t.Deps {
				depTarget := g.Targets[d]
				if depTarget == nil {
					return fmt.Errorf("couldn't find target %v in g.Targets\n", d)
				}
				if _, ok := seenTargets[d]; !ok {
					toProcessNext = append(toProcessNext, depTarget)
				}
			}

			var cleanDepsFilter []string
			for _, d := range t.CleanDeps {
				if excludeTargets[d] {
					continue
				}
				cleanDepsFilter = append(cleanDepsFilter, d)
			}
			t.CleanDeps = cleanDepsFilter
		}
		toProcess = toProcessNext
	}

	g.Targets = seenTargets
	return nil
}