package inventory

import (
	"context"
	"sort"
	"strings"

	"github.com/novox/mesh-controller/internal/catalogue"
)

// The kinds of edge in the catalogue's one dependency relation (novox/hq ADR 0162).
const (
	// EdgeStandsOn: the module's artifact is built on the other's.
	EdgeStandsOn = "stands-on"
	// EdgePackages: the module's build reads the other's repository.
	EdgePackages = "packages"
	// EdgeBuiltBy: the module is built by the holder of the build-machine seat.
	EdgeBuiltBy = "built-by"
	// EdgeDeclared: the manifest's own `build.on`.
	EdgeDeclared = "declared"
)

// Edge is one dependency: From depends on To, in the way Kind says.
type Edge struct {
	From string `json:"from"`
	To   string `json:"to"`
	Kind string `json:"kind"`
}

// Dependencies is the catalogue's dependency relation, whole: every module the mesh holds, with
// an edge to each module it depends on and the kind of dependency on the edge. One answer, so
// nothing else computes an edge (novox/hq ADR 0162) — the merge handler, `build --on` and the
// overview all read this.
//
// Four sources, one relation: a manifest's `build.on`; the artifacts the latest build was made
// against (an `artifact-store://<module>/…` reference is an edge to that module); the repositories
// the latest build read (an edge to the module whose source that is); and the build machine, which
// every source-built module is built by.
func (i *Inventory) Dependencies(ctx context.Context) ([]Edge, error) {
	entries, err := i.Catalogued(ctx)
	if err != nil {
		return nil, err
	}
	against, err := i.BuiltAgainst(ctx)
	if err != nil {
		return nil, err
	}
	read, err := i.ReadRepositories(ctx)
	if err != nil {
		return nil, err
	}
	return dependenciesOf(entries, against, read), nil
}

// dependenciesOf is Dependencies over what was read, so a test can hand it a catalogue.
func dependenciesOf(entries []Entry, against map[string][]string, read map[string][]ReadRepository) []Edge {
	known := map[string]bool{}
	byRepository := map[string][]string{}
	var builders []string
	for _, e := range entries {
		name := e.Manifest.Module
		known[name] = true
		if r := repositoryKey(e.Source.Repository); r != "" {
			byRepository[r] = append(byRepository[r], name)
		}
		if e.Manifest.ClaimsSeat("mesh-build-machine") {
			builders = append(builders, name)
		}
	}
	seen := map[Edge]bool{}
	var out []Edge
	add := func(from, to, kind string) {
		if from == to || !known[to] {
			return
		}
		e := Edge{From: from, To: to, Kind: kind}
		if !seen[e] {
			seen[e] = true
			out = append(out, e)
		}
	}
	for _, e := range entries {
		name := e.Manifest.Module
		if e.Manifest.Build != nil {
			for _, on := range e.Manifest.Build.On {
				if on.Module != "" {
					add(name, on.Module, EdgeDeclared)
				}
			}
		}
		for _, ref := range against[name] {
			if rest, ok := strings.CutPrefix(ref, catalogue.ArtifactStoreScheme); ok {
				if base, _, found := strings.Cut(rest, "/"); found {
					add(name, base, EdgeStandsOn)
				}
			}
		}
		for _, r := range read[name] {
			for _, other := range byRepository[repositoryKey(r.Repository)] {
				add(name, other, EdgePackages)
			}
		}
		if e.Source.Repository != "" {
			for _, b := range builders {
				add(name, b, EdgeBuiltBy)
			}
		}
	}
	sort.Slice(out, func(a, b int) bool {
		if out[a].From != out[b].From {
			return out[a].From < out[b].From
		}
		if out[a].To != out[b].To {
			return out[a].To < out[b].To
		}
		return out[a].Kind < out[b].Kind
	})
	return out
}

// repositoryKey is a repository as compared: lower-cased, without a trailing `.git`.
func repositoryKey(repository string) string {
	return strings.ToLower(strings.TrimSuffix(strings.TrimSpace(repository), ".git"))
}