package state

import (
	"fmt"
	"sort"
	"sync"

	"github.com/roboll/helmfile/pkg/helmexec"
	"github.com/variantdev/dag/pkg/dag"
)

type result struct {
	release ReleaseSpec
	err     error
}

func (st *HelmState) scatterGather(concurrency int, items int, produceInputs func(), receiveInputsAndProduceIntermediates func(int), aggregateIntermediates func()) {

	if concurrency < 1 || concurrency > items {
		concurrency = items
	}

	for _, r := range st.Releases {
		if r.Tillerless != nil {
			if *r.Tillerless {
				concurrency = 1
			}
		} else if st.HelmDefaults.Tillerless {
			concurrency = 1
		}
	}

	// WaitGroup is required to wait until goroutine per job in job queue cleanly stops.
	var waitGroup sync.WaitGroup
	waitGroup.Add(concurrency)

	go produceInputs()

	for w := 1; w <= concurrency; w++ {
		go func(id int) {
			receiveInputsAndProduceIntermediates(id)
			waitGroup.Done()
		}(w)
	}

	aggregateIntermediates()

	// Wait until all the goroutines to gracefully finish
	waitGroup.Wait()
}

func (st *HelmState) scatterGatherReleases(helm helmexec.Interface, concurrency int,
	do func(ReleaseSpec, int) error) []error {

	return st.iterateOnReleases(helm, concurrency, st.Releases, do)
}

func (st *HelmState) iterateOnReleases(helm helmexec.Interface, concurrency int, inputs []ReleaseSpec,
	do func(ReleaseSpec, int) error) []error {
	var errs []error

	inputsSize := len(inputs)

	releases := make(chan ReleaseSpec)
	results := make(chan result)

	st.scatterGather(
		concurrency,
		inputsSize,
		func() {
			for _, release := range inputs {
				releases <- release
			}
			close(releases)
		},
		func(id int) {
			for release := range releases {
				err := do(release, id)
				st.logger.Debugf("release %q processed", release.Name)
				results <- result{release: release, err: err}
			}
		},
		func() {
			for range inputs {
				r := <-results
				if r.err != nil {
					errs = append(errs, fmt.Errorf("release \"%s\" failed: %v", r.release.Name, r.err))
				}
			}
		},
	)

	if len(errs) != 0 {
		return errs
	}

	return nil
}

type PlanOpts struct {
	Reverse bool
}

func (st *HelmState) PlanReleases(reverse bool) ([][]Release, error) {
	marked, err := st.SelectReleasesWithOverrides()
	if err != nil {
		return nil, err
	}

	groups, err := SortedReleaseGroups(marked, reverse)
	if err != nil {
		return nil, err
	}

	return groups, nil
}

func SortedReleaseGroups(releases []Release, reverse bool) ([][]Release, error) {
	groups, err := GroupReleasesByDependency(releases)
	if err != nil {
		return nil, err
	}

	if reverse {
		sort.Slice(groups, func(i, j int) bool {
			return j < i
		})
	}

	return groups, nil
}

func GroupReleasesByDependency(releases []Release) ([][]Release, error) {
	idToReleases := map[string][]Release{}
	idToIndex := map[string]int{}

	d := dag.New()
	for i, r := range releases {

		id := ReleaseToID(&r.ReleaseSpec)

		idToReleases[id] = append(idToReleases[id], r)
		idToIndex[id] = i

		// Only compute dependencies from non-filtered releases
		if !r.Filtered {
			d.Add(id, dag.Dependencies(r.Needs))
		}
	}

	for _, r := range releases {
		if !r.Filtered {
			for _, n := range r.Needs {
				if _, ok := idToReleases[n]; !ok {
					id := ReleaseToID(&r.ReleaseSpec)
					return nil, fmt.Errorf("%q depends on nonexistent release %q", id, n)
				}
			}
		}
	}

	plan, err := d.Plan()
	if err != nil {
		return nil, err
	}

	var result [][]Release

	for groupIndex := 0; groupIndex < len(plan); groupIndex++ {
		dagNodesInGroup := plan[groupIndex]

		var idsInGroup []string
		var releasesInGroup []Release

		for _, node := range dagNodesInGroup {
			idsInGroup = append(idsInGroup, node.Id)
		}

		// Make the helmfile behavior deterministic for reproducibility and ease of testing
		// We try to keep the order of definitions to keep backward-compatibility
		// See https://github.com/roboll/helmfile/issues/988
		sort.Slice(idsInGroup, func(i, j int) bool {
			ii := idToIndex[idsInGroup[i]]
			ij := idToIndex[idsInGroup[j]]
			return ii < ij
		})

		for _, id := range idsInGroup {
			releases, ok := idToReleases[id]
			if !ok {
				panic(fmt.Errorf("bug: unexpectedly failed to get releases for id %q", id))
			}
			releasesInGroup = append(releasesInGroup, releases...)
		}

		result = append(result, releasesInGroup)
	}

	return result, nil
}