package bnp

import (
	"bytes"
	"context"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"regexp"
	"sort"
	"strconv"

	abiv1 "git.dev.alexdunmow.com/block/core/abi/v1"
	core "git.dev.alexdunmow.com/block/core/plugin"
	"google.golang.org/protobuf/proto"
)

// Required top-level artifact members (mirrors the CMS reader).
const (
	fileWasm     = "plugin.wasm"
	fileMod      = "plugin.mod"
	fileManifest = "manifest.pb"
)

// minGoMajor/minGoMinor is the lowest Go toolchain that can emit reactor-mode
// (`-buildmode=c-shared`) wasip1 modules the guest shim relies on.
const (
	minGoMajor = 1
	minGoMinor = 24
)

// BuildOptions configures Build.
type BuildOptions struct {
	// Dir is the plugin repo root (holds plugin.mod and the main Go package).
	Dir string
	// Output is the destination .bnp path. Empty → "<name>-<version>.bnp" in
	// the current working directory.
	Output string
}

// BuildResult summarizes a produced artifact for the CLI summary table.
type BuildResult struct {
	OutputPath    string
	Name          string
	Version       string
	// Codeless marks a declarative artifact (no plugin.wasm, WO-WZ-020).
	Codeless      bool
	WasmBytes     int64
	ManifestBytes int64
	ArtifactBytes int64 // on-disk .bnp size
	UncompBytes   int64 // sum of packed file sizes
	BlockCount    int
	TemplateCount int
	AdminPages    int
	JobTypes      int
	Hooks         []string
	DataDir       bool
	IncludedDirs  []string
}

// Build compiles the plugin in opts.Dir to wasm, extracts its manifest, and
// packs a .bnp. No Docker/podman: the whole pipeline is the local Go
// toolchain + wazero + tar.zst.
func Build(ctx context.Context, opts BuildOptions) (*BuildResult, error) {
	dir := opts.Dir
	if dir == "" {
		dir = "."
	}
	dir, err := filepath.Abs(dir)
	if err != nil {
		return nil, fmt.Errorf("resolve dir: %w", err)
	}

	modPath := filepath.Join(dir, fileMod)
	modBytes, err := os.ReadFile(modPath)
	if err != nil {
		return nil, fmt.Errorf("read plugin.mod (is %s a plugin repo?): %w", dir, err)
	}
	mod, err := core.ParseModFull(modBytes)
	if err != nil {
		return nil, fmt.Errorf("parse plugin.mod: %w", err)
	}
	if mod.Plugin.Name == "" || mod.Plugin.Version == "" {
		return nil, fmt.Errorf("plugin.mod must set both name and version")
	}

	if err := checkGoVersion(ctx); err != nil {
		return nil, err
	}

	// 1. Compile to reactor-mode wasip1 c-shared.
	tmp, err := os.MkdirTemp("", "ninja-build-*")
	if err != nil {
		return nil, fmt.Errorf("temp dir: %w", err)
	}
	defer func() { _ = os.RemoveAll(tmp) }()
	wasmPath := filepath.Join(tmp, fileWasm)
	if err := buildWasm(ctx, dir, wasmPath); err != nil {
		return nil, err
	}

	// 2. Extract the manifest by driving DESCRIBE.
	wasm, err := readWasm(wasmPath)
	if err != nil {
		return nil, err
	}
	manifest, err := ExtractManifest(ctx, wasm)
	if err != nil {
		return nil, fmt.Errorf("extract manifest: %w", err)
	}

	// 3. Validate against plugin.mod before packing an incoherent artifact.
	if manifest.GetName() != mod.Plugin.Name {
		return nil, fmt.Errorf("manifest name %q != plugin.mod name %q", manifest.GetName(), mod.Plugin.Name)
	}
	if v := manifest.GetAbiVersion(); v != hostAbiVersion {
		return nil, fmt.Errorf("manifest abi_version %d unsupported (packer speaks %d)", v, hostAbiVersion)
	}

	// 4. Stamp the data_dir grant from plugin.mod. DESCRIBE cannot see
	//    plugin.mod (it lives outside guest code), so the packer is where the
	//    grant crosses from mod → manifest; the loader then reads one source.
	manifest.DataDir = mod.Plugin.DataDir

	// 4b. Mixed-form artifacts (WO-WZ-021): a reduced wasm plugin may keep a
	//     minimal guest for genuine logic (a contact route, Stripe) while its
	//     declarative surfaces (theme presets, bundled fonts, master pages,
	//     system/page templates, template overrides, email wrappers, css,
	//     required icon packs) live in an optional root manifest.yaml — exactly
	//     the codeless declarative set. Fold it into the DESCRIBE-derived
	//     manifest just as BuildCodeless does: the declarative keys
	//     supplement/override the guest's, and the referenced root JSON
	//     (presets.json / master_pages.json / fonts.json) is embedded into
	//     manifest.pb (not packed separately, same as codeless). The templates/
	//     dir carrying the .ninjatpl sources already rides the optional-dir
	//     pack below. A repo with NO manifest.yaml is a no-op here
	//     (applyManifestYAML returns nil on os.IsNotExist), so an existing
	//     pure-wasm plugin builds byte-for-byte as before.
	if err := applyManifestYAML(dir, manifest); err != nil {
		return nil, err
	}

	manifestBytes, err := proto.Marshal(manifest)
	if err != nil {
		return nil, fmt.Errorf("marshal manifest.pb: %w", err)
	}

	// 5. Assemble artifact entries.
	entries := []packEntry{
		{ArtifactPath: fileWasm, Source: wasmPath},
		{ArtifactPath: fileMod, Source: modPath},
		{ArtifactPath: fileManifest, Data: manifestBytes},
	}
	var includedDirs []string
	// dir-name → source subpath. web ships the Module Federation build output
	// (web/dist) flattened under web/ so the reader's dirExists("web") fires.
	optional := []struct{ artifact, src string }{
		{dirBlocks, dirBlocks},
		{dirTemplates, dirTemplates},
		{dirSeed, dirSeed},
		{"migrations", "migrations"},
		{"schemas", "schemas"},
		{"assets", "assets"},
		{"web", filepath.Join("web", "dist")},
	}
	// Declarative dirs ride along on wasm artifacts too (a reduced plugin may
	// mix definition-backed blocks with logic); validate them identically.
	if _, err := validateBlocksDir(dir); err != nil {
		return nil, err
	}
	if err := validateSeedDir(dir); err != nil {
		return nil, err
	}
	for _, o := range optional {
		dirEntries, has, dErr := collectDir(filepath.Join(dir, o.src), o.artifact)
		if dErr != nil {
			return nil, dErr
		}
		if has {
			entries = append(entries, dirEntries...)
			includedDirs = append(includedDirs, o.artifact)
		}
	}

	// 6. Pack.
	outPath := opts.Output
	if outPath == "" {
		outPath = fmt.Sprintf("%s-%s.bnp", mod.Plugin.Name, mod.Plugin.Version)
	}
	uncomp, err := packArtifact(outPath, entries)
	if err != nil {
		return nil, err
	}

	artInfo, err := os.Stat(outPath)
	if err != nil {
		return nil, fmt.Errorf("stat artifact: %w", err)
	}
	wasmInfo, _ := os.Stat(wasmPath)

	return &BuildResult{
		OutputPath:    outPath,
		Name:          manifest.GetName(),
		Version:       manifest.GetVersion(),
		WasmBytes:     wasmInfo.Size(),
		ManifestBytes: int64(len(manifestBytes)),
		ArtifactBytes: artInfo.Size(),
		UncompBytes:   uncomp,
		BlockCount:    len(manifest.GetBlocks()),
		TemplateCount: len(manifest.GetTemplateKeys()),
		AdminPages:    len(manifest.GetAdminPages()),
		JobTypes:      len(manifest.GetJobTypes()),
		Hooks:         hooksPresent(manifest),
		DataDir:       manifest.GetDataDir(),
		IncludedDirs:  includedDirs,
	}, nil
}

// buildWasm runs the reactor-mode wasip1 c-shared build in dir.
func buildWasm(ctx context.Context, dir, outPath string) error {
	cmd := exec.CommandContext(ctx, "go", "build", "-buildmode=c-shared", "-o", outPath, ".")
	cmd.Dir = dir
	cmd.Env = append(os.Environ(), "GOOS=wasip1", "GOARCH=wasm")
	var stderr bytes.Buffer
	cmd.Stderr = &stderr
	if err := cmd.Run(); err != nil {
		return fmt.Errorf("go build (GOOS=wasip1 GOARCH=wasm -buildmode=c-shared) failed: %w\n%s", err, stderr.String())
	}
	return nil
}

var goVersionRe = regexp.MustCompile(`go(\d+)\.(\d+)(?:\.\d+)?`)

// checkGoVersion enforces the minimum toolchain (Go 1.24) with a clear error.
func checkGoVersion(ctx context.Context) error {
	out, err := exec.CommandContext(ctx, "go", "version").Output()
	if err != nil {
		return fmt.Errorf("`go version` failed (is the Go toolchain on PATH?): %w", err)
	}
	m := goVersionRe.FindStringSubmatch(string(out))
	if m == nil {
		return fmt.Errorf("could not parse Go version from %q", string(out))
	}
	major, _ := strconv.Atoi(m[1])
	minor, _ := strconv.Atoi(m[2])
	if major < minGoMajor || (major == minGoMajor && minor < minGoMinor) {
		return fmt.Errorf(
			"building reactor-mode wasip1 plugins requires Go %d.%d+; found %d.%d — upgrade your toolchain",
			minGoMajor, minGoMinor, major, minor)
	}
	return nil
}

// hooksPresent returns the sorted set of runtime hooks the manifest declares,
// for the summary table.
func hooksPresent(m *abiv1.PluginManifest) []string {
	var hooks []string
	if m.GetHasLoadHook() {
		hooks = append(hooks, "load")
	}
	if m.GetHasUnloadHook() {
		hooks = append(hooks, "unload")
	}
	if m.GetHasHttpHandler() {
		hooks = append(hooks, "http")
	}
	if m.GetHasMediaHooks() {
		hooks = append(hooks, "media")
	}
	if len(m.GetJobTypes()) > 0 {
		hooks = append(hooks, "job")
	}
	if len(m.GetRagContentFetcherTypes()) > 0 {
		hooks = append(hooks, "rag")
	}
	sort.Strings(hooks)
	return hooks
}