// Package composer is the node-engine's composition as one function over a plain request (novox/hq ADR 0482 clause 4,
// ADR 0593 §7): what the command mesh-compose runs, so a group that changes the node-engine's composition is composed by
// the composer built at that group's head of the node-engine's repository, in a build module's sandbox.
//
// **It reads its request and nothing else.** No bus, store, network, file or environment: the manifests come inside the
// request (raw, as their repository holds them), the rest of the mesh is the request's input, and the answer is a value.
// The request's and the verdict's shapes are mesh-sdk's composer package; their logic, which composes, is here.
package composer

import (
	"encoding/json"
	"fmt"
	"slices"
	"sort"

	"git.novox.be/novox/mesh-sdk/go/catalogue"
	sdk "git.novox.be/novox/mesh-sdk/go/composer"
	"git.novox.be/novox/mesh-sdk/go/delivery"
	"git.novox.be/novox/mesh-sdk/go/sdkversion"

	"github.com/novox/mesh-host/internal/compose"
	"github.com/novox/mesh-host/internal/compose/frombus"
)

// The shapes of mesh-sdk's composer package, by the names this package's code was written with.
type (
	Request      = sdk.Request
	Case         = sdk.Case
	Manifest     = sdk.Manifest
	Verdict      = sdk.Verdict
	CaseVerdict  = sdk.CaseVerdict
	ManifestRead = sdk.ManifestRead
	Machine      = sdk.Machine
	Path         = sdk.Path
)

const (
	Version      = sdk.Version
	DepthResolve = sdk.DepthResolve
	DepthCompose = sdk.DepthCompose
)

// ErrUnfilled is a manifest named by a digest that nobody replaced by its bytes (sdk.ErrUnfilled).
var ErrUnfilled = sdk.ErrUnfilled

// inputOf is the request's input as this composer's composition input: the request carries it as JSON (mesh-sdk holds no
// composition), the same bytes either way.
func inputOf(r Request) (compose.Input, error) {
	var in compose.Input
	raw, err := json.Marshal(r.Input)
	if err != nil {
		return in, fmt.Errorf("composer: the request's input cannot be read: %w", err)
	}
	if len(raw) == 0 || string(raw) == "null" {
		return in, nil
	}
	if err := json.Unmarshal(raw, &in); err != nil {
		return in, fmt.Errorf("composer: the request's input is not a composition input: %w", err)
	}
	return in, nil
}

// Run composes every case of r and answers the verdict, its SDK this binary's mesh-sdk. An error is a request it
// cannot run (an unknown depth, a case named twice, a manifest left as a digest); a machine that does not compose is a
// verdict.
func Run(r Request) (Verdict, error) {
	depth := r.Depth
	if depth == "" {
		depth = DepthCompose
	}
	if depth != DepthResolve && depth != DepthCompose {
		return Verdict{}, fmt.Errorf("composer: the depth %q is not resolve or compose", r.Depth)
	}
	v := Verdict{V: Version, SDK: sdkversion.Version()}
	seen := map[string]bool{}
	for _, c := range r.Cases {
		if seen[c.Name] {
			return Verdict{}, fmt.Errorf("composer: the case %q is named twice", c.Name)
		}
		seen[c.Name] = true
		cv, err := runCase(r, c, depth)
		if err != nil {
			return Verdict{}, err
		}
		v.Cases = append(v.Cases, cv)
	}
	return v, nil
}

// parse decodes every manifest leniently and takes its verdict (novox/hq ADR 0578 §3, §5): the composer judges none. A
// manifest refused by its verdict is held, composed as its stub without its items (as the bus reader holds one); bytes
// that do not decode are left out. Both are named in reads.
func parse(m map[string]Manifest, reads map[string]ManifestRead, verdicts map[string]delivery.ManifestVerdict) (map[string]catalogue.Manifest, error) {
	out := map[string]catalogue.Manifest{}
	for name, man := range m {
		if len(man.Raw) == 0 {
			return nil, fmt.Errorf("%w: %s (digest %s)", ErrUnfilled, name, man.Digest)
		}
		decoded, err := catalogue.Decode(man.Raw)
		read := ManifestRead{Accepted: err == nil, SetAside: decoded.SetAside()}
		if err != nil {
			read.Refused = fmt.Sprintf("the manifest of %s does not decode: %v", name, err)
		} else if v, ok := verdicts[name]; ok {
			if refused, _ := delivery.TakeManifestVerdict(&v); refused {
				if v.Module == "" {
					v.Module = name
				}
				read = ManifestRead{Refused: v.Why()}
				decoded.Items = nil
				decoded = compose.Stub(decoded)
			}
		}
		if reads != nil {
			reads[name] = read
		}
		if err == nil {
			out[name] = decoded
		}
	}
	return out, nil
}

func runCase(r Request, c Case, depth string) (CaseVerdict, error) {
	cv := CaseVerdict{Name: c.Name, Manifests: map[string]ManifestRead{}}
	shelf, err := parse(c.Manifests, cv.Manifests, c.Verdicts)
	if err != nil {
		return CaseVerdict{}, err
	}
	base, err := inputOf(r)
	if err != nil {
		return CaseVerdict{}, err
	}
	in, err := frombus.Placed(base, c.Placements)
	if err != nil {
		return CaseVerdict{}, fmt.Errorf("composer: the case %q: %w", c.Name, err)
	}
	// The module the mesh provides itself (the private network) has no repository the indexer reads, so no case carries
	// it: its manifest comes with mesh-sdk and always wins, as the bus reader has it (frombus readBase). Without it a node
	// it is assigned to composed nothing (issue 1126, check of mesh-host #200: "nothing provides mesh-wireguard").
	for _, name := range delivery.ProvidedModules() {
		m, _, err := delivery.ProvidedManifest(name)
		if err != nil {
			return CaseVerdict{}, fmt.Errorf("composer: %w", err)
		}
		shelf[name] = m
	}
	in.Catalogue = shelf
	in.Nodes = slices.Clone(in.Nodes)
	in.Holdings = slices.Clone(in.Holdings)
	for i := range in.Nodes {
		in.Nodes[i].Kept = nil
		if kept := c.Kept[in.Nodes[i].Name]; len(kept) > 0 {
			k, err := parse(kept, nil, nil)
			if err != nil {
				return CaseVerdict{}, err
			}
			in.Nodes[i].Kept = k
		}
	}
	if r.HoldingsFromClaims {
		in.Holdings = append(in.Holdings, HoldingsOf(shelf, in.Nodes)...)
	}
	if len(r.Machines) == 0 {
		return cv, nil
	}
	cv.Machines = map[string]Machine{}
	for _, node := range r.Machines {
		cv.Machines[node] = machine(in, node, depth, r.Declarations)
	}
	return cv, nil
}

// HoldingsOf is every seat an assigned module claims, held on the node it is assigned to, in node order: the holdings
// of an input that has none of record (the assigner's, mesh-delivery-assigner internal/assign input).
func HoldingsOf(shelf map[string]catalogue.Manifest, nodes []compose.Node) []catalogue.Held {
	var out []catalogue.Held
	sorted := slices.Clone(nodes)
	sort.Slice(sorted, func(i, j int) bool { return sorted[i].Name < sorted[j].Name })
	for _, n := range sorted {
		for _, mod := range n.Assigned {
			for _, cl := range shelf[mod].Claims {
				scope := cl.Scope
				if seat, ok := catalogue.SeatNamed(cl.Name); ok && scope == "" {
					scope = seat.Scope
				}
				out = append(out, catalogue.Held{Claim: cl.Name, Scope: scope, Node: n.Name, Module: mod})
			}
		}
	}
	return out
}

func machine(in compose.Input, node, depth string, declarations bool) Machine {
	if depth == DepthResolve {
		if _, err := compose.Resolve(in, node); err != nil {
			return Machine{Reason: err.Error()}
		}
		return Machine{Composes: true}
	}
	d, problems, err := compose.Compose(in, node)
	if err != nil {
		return Machine{Reason: err.Error()}
	}
	m := Machine{Composes: len(problems) == 0, Problems: problems, Refusals: d.Refusals()}
	if len(problems) > 0 {
		m.Reason = "the node-engine's validator refuses the declaration"
	}
	if declarations {
		m.Declared = pathsOf(d)
	}
	return m
}

// pathsOf is every resource of a declaration that names a path, with its owner, group and mode as declared, sorted by
// path.
func pathsOf(d compose.Declared) []Path {
	var out []Path
	str := func(r map[string]any, key string) string {
		if v, ok := r[key]; ok && v != nil {
			return fmt.Sprint(v)
		}
		return ""
	}
	for _, r := range d.Resources {
		p := str(r, "path")
		if p == "" {
			continue
		}
		out = append(out, Path{Path: p, Kind: str(r, "type"), Owner: str(r, "owner"), Group: str(r, "group"),
			Mode: str(r, "mode"), Module: d.ModuleOf[str(r, "id")]})
	}
	sort.Slice(out, func(i, j int) bool {
		if out[i].Path != out[j].Path {
			return out[i].Path < out[j].Path
		}
		return out[i].Kind < out[j].Kind
	})
	return out
}

// Package is the import path of the command, which a build module builds at the node-engine's repository's head of a
// group that changes the node-engine's composition (novox/hq ADR 0593 §7): mesh-sdk's composer.Package names the same.
const Package = "github.com/novox/mesh-host/cmd/mesh-compose"

// Decode reads a request (sdk.Decode); it refuses one that is not JSON or of another version.
func Decode(data []byte) (Request, error) { return sdk.Decode(data) }