package ops

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"os"
	"path"
	"runtime"
	"sort"
	"strings"

	"github.com/containerd/platforms"
	"github.com/moby/buildkit/cache"
	"github.com/moby/buildkit/executor"
	resourcestypes "github.com/moby/buildkit/executor/resources/types"
	"github.com/moby/buildkit/frontend/gateway/container"
	"github.com/moby/buildkit/session"
	"github.com/moby/buildkit/session/secrets"
	"github.com/moby/buildkit/solver"
	"github.com/moby/buildkit/solver/llbsolver/errdefs"
	"github.com/moby/buildkit/solver/llbsolver/mounts"
	"github.com/moby/buildkit/solver/llbsolver/ops/opsutils"
	"github.com/moby/buildkit/solver/pb"
	"github.com/moby/buildkit/util/progress/logs"
	utilsystem "github.com/moby/buildkit/util/system"
	"github.com/moby/buildkit/worker"
	digest "github.com/opencontainers/go-digest"
	ocispecs "github.com/opencontainers/image-spec/specs-go/v1"
	"github.com/pkg/errors"
	"go.opentelemetry.io/otel/trace"
	"golang.org/x/sync/semaphore"
)

const execCacheType = "buildkit.exec.v0"

type ExecOp struct {
	op          *pb.ExecOp
	cm          cache.Manager
	mm          *mounts.MountManager
	sm          *session.Manager
	exec        executor.Executor
	w           worker.Worker
	platform    *pb.Platform
	numInputs   int
	parallelism *semaphore.Weighted
	rec         resourcestypes.Recorder
	digest      digest.Digest
}

var _ solver.Op = &ExecOp{}

func NewExecOp(v solver.Vertex, op *pb.Op_Exec, platform *pb.Platform, cm cache.Manager, parallelism *semaphore.Weighted, sm *session.Manager, exec executor.Executor, w worker.Worker) (*ExecOp, error) {
	if err := opsutils.Validate(&pb.Op{Op: op}); err != nil {
		return nil, err
	}
	name := fmt.Sprintf("exec %s", strings.Join(op.Exec.Meta.Args, " "))
	return &ExecOp{
		op:          op.Exec,
		mm:          mounts.NewMountManager(name, cm, sm),
		cm:          cm,
		sm:          sm,
		exec:        exec,
		numInputs:   len(v.Inputs()),
		w:           w,
		platform:    platform,
		parallelism: parallelism,
		digest:      v.Digest(),
	}, nil
}

func (e *ExecOp) Digest() digest.Digest {
	return e.digest
}

func (e *ExecOp) Proto() *pb.ExecOp {
	return e.op
}

func cloneExecOp(old *pb.ExecOp) pb.ExecOp {
	n := *old
	meta := *n.Meta
	meta.ExtraHosts = nil
	for i := range n.Meta.ExtraHosts {
		h := *n.Meta.ExtraHosts[i]
		meta.ExtraHosts = append(meta.ExtraHosts, &h)
	}
	n.Meta = &meta
	n.Mounts = nil
	for i := range old.Mounts {
		m := *old.Mounts[i]

		if m.CacheOpt != nil {
			co := *m.CacheOpt
			m.CacheOpt = &co
		}

		n.Mounts = append(n.Mounts, &m)
	}
	return n
}

func checkShouldClearCacheOpts(m *pb.Mount) bool {
	if m.CacheOpt == nil {
		return false
	}

	// This is a dockerfile default cache mount.
	// We are treating this as a special case so we don't cause a cache miss unintentionally.
	if m.CacheOpt.ID == m.Dest && m.CacheOpt.Sharing == 0 {
		return false
	}

	// Check the case where a dockerfile cache-namespace may be used.
	// This would be `<namespace>/<dest>`
	_, trimmed, ok := strings.Cut(m.CacheOpt.ID, "/")
	if ok && trimmed == m.Dest && m.CacheOpt.Sharing == 0 {
		return false
	}

	return true
}

func (e *ExecOp) CacheMap(ctx context.Context, g session.Group, index int) (*solver.CacheMap, bool, error) {
	op := cloneExecOp(e.op)

	for i := range op.Meta.ExtraHosts {
		h := op.Meta.ExtraHosts[i]
		h.IP = ""
		op.Meta.ExtraHosts[i] = h
	}

	for i := range op.Mounts {
		m := op.Mounts[i]
		m.Selector = ""

		if checkShouldClearCacheOpts(m) {
			m.CacheOpt.ID = ""
			m.CacheOpt.Sharing = 0
		}
	}
	op.Meta.ProxyEnv = nil

	p := platforms.DefaultSpec()
	if e.platform != nil {
		p = ocispecs.Platform{
			OS:           e.platform.OS,
			Architecture: e.platform.Architecture,
			Variant:      e.platform.Variant,
			OSVersion:    e.platform.OSVersion,
			OSFeatures:   e.platform.OSFeatures,
		}
	}

	// Special case for cache compatibility with buggy versions that wrongly
	// excluded Exec.Mounts: for the default case of one root mount (i.e. RUN
	// inside a Dockerfile), do not include the mount when generating the cache
	// map.
	if len(op.Mounts) == 1 &&
		op.Mounts[0].Dest == "/" &&
		op.Mounts[0].Selector == "" &&
		!op.Mounts[0].Readonly &&
		op.Mounts[0].MountType == pb.MountType_BIND &&
		op.Mounts[0].CacheOpt == nil &&
		op.Mounts[0].SSHOpt == nil &&
		op.Mounts[0].SecretOpt == nil &&
		op.Mounts[0].ResultID == "" {
		op.Mounts = nil
	}

	dt, err := json.Marshal(struct {
		Type       string
		Exec       *pb.ExecOp
		OS         string
		Arch       string
		Variant    string   `json:",omitempty"`
		OSVersion  string   `json:",omitempty"`
		OSFeatures []string `json:",omitempty"`
	}{
		Type:       execCacheType,
		Exec:       &op,
		OS:         p.OS,
		Arch:       p.Architecture,
		Variant:    p.Variant,
		OSVersion:  p.OSVersion,
		OSFeatures: p.OSFeatures,
	})
	if err != nil {
		return nil, false, err
	}

	cm := &solver.CacheMap{
		Digest: digest.FromBytes(dt),
		Deps: make([]struct {
			Selector          digest.Digest
			ComputeDigestFunc solver.ResultBasedCacheFunc
			PreprocessFunc    solver.PreprocessFunc
		}, e.numInputs),
	}

	deps, err := e.getMountDeps()
	if err != nil {
		return nil, false, err
	}

	for i, dep := range deps {
		if len(dep.Selectors) != 0 {
			dgsts := make([][]byte, 0, len(dep.Selectors))
			for _, p := range dep.Selectors {
				dgsts = append(dgsts, []byte(p))
			}
			cm.Deps[i].Selector = digest.FromBytes(bytes.Join(dgsts, []byte{0}))
		}
		if dep.ContentBasedHash {
			cm.Deps[i].ComputeDigestFunc = opsutils.NewContentHashFunc(toSelectors(dedupePaths(dep.Selectors)))
		}
		cm.Deps[i].PreprocessFunc = unlazyResultFunc
	}

	return cm, true, nil
}

func dedupePaths(inp []string) []string {
	// If there's one or fewer inputs, then dedupe won't do anything.
	// Skip the allocations and logic of this function in that case.
	if len(inp) <= 1 {
		return inp
	}

	old := make(map[string]struct{}, len(inp))
	for _, p := range inp {
		old[p] = struct{}{}
	}
	paths := make([]string, 0, len(old))
	for p1 := range old {
		var skip bool
		for p2 := range old {
			// Check if p2 is a prefix of p1. Ensure that p2 ends in a slash
			// so that we know p2 is a parent directory of p1. We don't want
			// /foo to be a parent of /foobar.
			if p1 != p2 && strings.HasPrefix(p1, forceTrailingSlash(p2)) {
				skip = true
				break
			}
		}
		if !skip {
			paths = append(paths, p1)
		}
	}
	sort.Slice(paths, func(i, j int) bool {
		return paths[i] < paths[j]
	})
	return paths
}

// forceTrailingSlash ensures that the path always ends with a path separator.
// If the path already ends with a /, this method returns the same string.
func forceTrailingSlash(s string) string {
	if strings.HasSuffix(s, "/") {
		return s
	}
	return s + "/"
}

func toSelectors(p []string) []opsutils.Selector {
	sel := make([]opsutils.Selector, 0, len(p))
	for _, p := range p {
		if p == "" || p == "/" {
			return nil
		}
		sel = append(sel, opsutils.Selector{Path: p, FollowLinks: true})
	}
	return sel
}

type dep struct {
	Selectors []string

	// ContentBasedHash enables content-based caching. This is used to ensure
	// that all caching is done safely and efficiently.
	ContentBasedHash bool
}

func (e *ExecOp) getMountDeps() ([]dep, error) {
	deps := make([]dep, e.numInputs)
	for _, m := range e.op.Mounts {
		if m.Input == pb.Empty {
			continue
		}
		if int(m.Input) >= len(deps) {
			return nil, errors.Errorf("invalid mountinput %v", m)
		}

		sel := path.Join("/", m.Selector)
		deps[m.Input].Selectors = append(deps[m.Input].Selectors, sel)

		// Assume that we *cannot* perform content-based caching, and then
		// enable it selectively only for cases where we want to
		contentBasedCache := false

		// Allow content-based cached where safe - these are enforced to avoid
		// the following case:
		// - A "snapshot" contains "foo/a.txt" and "bar/b.txt"
		// - "RUN --mount from=snapshot,src=bar touch bar/c.txt" creates a new
		//   file in bar
		// - If we run again, but this time "snapshot" contains a new
		//   "foo/sneaky.txt", the content-based cache matches the previous
		//   run, since we only select "bar"
		// - But this cached result is incorrect - "foo/sneaky.txt" isn't in
		//   our cached result, but it is in our input.
		if m.Output == pb.SkipOutput {
			// if the mount has no outputs, it's safe to enable content-based
			// caching, since it's guaranteed to not be used as an input for
			// any future steps
			contentBasedCache = true
		} else if m.Readonly {
			// if the mount is read-only, then it's also safe, since it can't
			// be modified by the operation
			contentBasedCache = true
		} else if sel == pb.RootMount {
			// if the mount mounts the entire source, then it's also safe,
			// since there are no unselected "sneaky" files
			contentBasedCache = true
		}

		// Now apply the user-specified option.
		switch m.ContentCache {
		case pb.MountContentCache_OFF:
			contentBasedCache = false
		case pb.MountContentCache_ON:
			if !contentBasedCache {
				// If we can't enable cache for safety, then force-enabling it is invalid
				return nil, errors.Errorf("invalid mount cache content %v", m)
			}
		case pb.MountContentCache_DEFAULT:
			if m.Dest == pb.RootMount {
				// we explicitly choose to not implement it on the root mount,
				// since this is likely very expensive (and not incredibly useful)
				contentBasedCache = false
			}
		}

		deps[m.Input].ContentBasedHash = contentBasedCache
	}
	return deps, nil
}

func addDefaultEnvvar(env []string, k, v string) []string {
	for _, e := range env {
		if strings.HasPrefix(e, k+"=") {
			return env
		}
	}
	return append(env, k+"="+v)
}

func (e *ExecOp) Exec(ctx context.Context, g session.Group, inputs []solver.Result) (results []solver.Result, err error) {
	trace.SpanFromContext(ctx).AddEvent("ExecOp started")

	refs := make([]*worker.WorkerRef, len(inputs))
	for i, inp := range inputs {
		var ok bool
		refs[i], ok = inp.Sys().(*worker.WorkerRef)
		if !ok {
			return nil, errors.Errorf("invalid reference for exec %T", inp.Sys())
		}
	}

	platformOS := runtime.GOOS
	if e.platform != nil {
		platformOS = e.platform.OS
	}
	p, err := container.PrepareMounts(ctx, e.mm, e.cm, g, e.op.Meta.Cwd, e.op.Mounts, refs, func(m *pb.Mount, ref cache.ImmutableRef) (cache.MutableRef, error) {
		desc := fmt.Sprintf("mount %s from exec %s", m.Dest, strings.Join(e.op.Meta.Args, " "))
		return e.cm.New(ctx, ref, g, cache.WithDescription(desc))
	}, platformOS)
	defer func() {
		if err != nil {
			execInputs := make([]solver.Result, len(e.op.Mounts))
			for i, m := range e.op.Mounts {
				if m.Input == -1 {
					continue
				}
				execInputs[i] = inputs[m.Input].Clone()
			}
			execMounts := make([]solver.Result, len(e.op.Mounts))
			copy(execMounts, execInputs)
			for i, res := range results {
				execMounts[p.OutputRefs[i].MountIndex] = res
			}
			for _, active := range p.Actives {
				if active.NoCommit {
					active.Ref.Release(context.TODO())
				} else {
					ref, cerr := active.Ref.Commit(ctx)
					if cerr != nil {
						err = errors.Wrapf(err, "error committing %s: %s", active.Ref.ID(), cerr)
						continue
					}
					execMounts[active.MountIndex] = worker.NewWorkerRefResult(ref, e.w)
				}
			}
			err = errdefs.WithExecError(err, execInputs, execMounts)
		} else {
			// Only release actives if err is nil.
			for i := len(p.Actives) - 1; i >= 0; i-- { // call in LIFO order
				p.Actives[i].Ref.Release(context.TODO())
			}
		}
		for _, o := range p.OutputRefs {
			if o.Ref != nil {
				o.Ref.Release(context.TODO())
			}
		}
	}()
	if err != nil {
		return nil, err
	}

	extraHosts, err := container.ParseExtraHosts(e.op.Meta.ExtraHosts)
	if err != nil {
		return nil, err
	}

	emu, err := getEmulator(ctx, e.platform)
	if err != nil {
		return nil, err
	}
	if emu != nil {
		e.op.Meta.Args = append([]string{qemuMountName}, e.op.Meta.Args...)

		p.Mounts = append(p.Mounts, executor.Mount{
			Readonly: true,
			Src:      emu,
			Dest:     qemuMountName,
		})
	}

	meta := executor.Meta{
		Args:                      e.op.Meta.Args,
		Env:                       e.op.Meta.Env,
		Cwd:                       e.op.Meta.Cwd,
		User:                      e.op.Meta.User,
		Hostname:                  e.op.Meta.Hostname,
		ReadonlyRootFS:            p.ReadonlyRootFS,
		ExtraHosts:                extraHosts,
		Ulimit:                    e.op.Meta.Ulimit,
		CgroupParent:              e.op.Meta.CgroupParent,
		NetMode:                   e.op.Network,
		SecurityMode:              e.op.Security,
		RemoveMountStubsRecursive: e.op.Meta.RemoveMountStubsRecursive,
	}

	if e.op.Meta.ProxyEnv != nil {
		meta.Env = append(meta.Env, proxyEnvList(e.op.Meta.ProxyEnv)...)
	}
	var currentOS string
	if e.platform != nil {
		currentOS = e.platform.OS
	}
	meta.Env = addDefaultEnvvar(meta.Env, "PATH", utilsystem.DefaultPathEnv(currentOS))

	secretEnv, err := e.loadSecretEnv(ctx, g)
	if err != nil {
		return nil, err
	}
	meta.Env = append(meta.Env, secretEnv...)

	stdout, stderr, flush := logs.NewLogStreams(ctx, os.Getenv("BUILDKIT_DEBUG_EXEC_OUTPUT") == "1")
	defer stdout.Close()
	defer stderr.Close()
	defer func() {
		if err != nil {
			flush()
		}
	}()

	rec, execErr := e.exec.Run(ctx, "", p.Root, p.Mounts, executor.ProcessInfo{
		Meta:   meta,
		Stdin:  nil,
		Stdout: stdout,
		Stderr: stderr,
	}, nil)

	for i, out := range p.OutputRefs {
		if mutable, ok := out.Ref.(cache.MutableRef); ok {
			ref, err := mutable.Commit(ctx)
			if err != nil {
				return nil, errors.Wrapf(err, "error committing %s", mutable.ID())
			}
			results = append(results, worker.NewWorkerRefResult(ref, e.w))
		} else {
			results = append(results, worker.NewWorkerRefResult(out.Ref.(cache.ImmutableRef), e.w))
		}
		// Prevent the result from being released.
		p.OutputRefs[i].Ref = nil
	}
	e.rec = rec
	return results, errors.Wrapf(execErr, "process %q did not complete successfully", strings.Join(e.op.Meta.Args, " "))
}

func proxyEnvList(p *pb.ProxyEnv) []string {
	out := []string{}
	if v := p.HttpProxy; v != "" {
		out = append(out, "HTTP_PROXY="+v, "http_proxy="+v)
	}
	if v := p.HttpsProxy; v != "" {
		out = append(out, "HTTPS_PROXY="+v, "https_proxy="+v)
	}
	if v := p.FtpProxy; v != "" {
		out = append(out, "FTP_PROXY="+v, "ftp_proxy="+v)
	}
	if v := p.NoProxy; v != "" {
		out = append(out, "NO_PROXY="+v, "no_proxy="+v)
	}
	if v := p.AllProxy; v != "" {
		out = append(out, "ALL_PROXY="+v, "all_proxy="+v)
	}
	return out
}

func (e *ExecOp) Acquire(ctx context.Context) (solver.ReleaseFunc, error) {
	if e.parallelism == nil {
		return func() {}, nil
	}
	err := e.parallelism.Acquire(ctx, 1)
	if err != nil {
		return nil, err
	}
	return func() {
		e.parallelism.Release(1)
	}, nil
}

func (e *ExecOp) loadSecretEnv(ctx context.Context, g session.Group) ([]string, error) {
	secretenv := e.op.Secretenv
	if len(secretenv) == 0 {
		return nil, nil
	}
	out := make([]string, 0, len(secretenv))
	for _, sopt := range secretenv {
		id := sopt.ID
		if id == "" {
			return nil, errors.Errorf("secret ID missing for %q environment variable", sopt.Name)
		}
		var dt []byte
		var err error
		err = e.sm.Any(ctx, g, func(ctx context.Context, _ string, caller session.Caller) error {
			dt, err = secrets.GetSecret(ctx, caller, id)
			if err != nil {
				if errors.Is(err, secrets.ErrNotFound) && sopt.Optional {
					return nil
				}
				return err
			}
			return nil
		})
		if err != nil {
			return nil, err
		}
		out = append(out, fmt.Sprintf("%s=%s", sopt.Name, string(dt)))
	}
	return out, nil
}

func (e *ExecOp) IsProvenanceProvider() {
}

func (e *ExecOp) Samples() (*resourcestypes.Samples, error) {
	if e.rec == nil {
		return nil, nil
	}
	return e.rec.Samples()
}