package bnp

import (
	"context"
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"strings"

	abiv1 "git.dev.alexdunmow.com/block/core/abi/v1"
	core "git.dev.alexdunmow.com/block/core/plugin"
	"google.golang.org/protobuf/proto"
	"gopkg.in/yaml.v3"
)

// Codeless artifacts (WO-WZ-020): a .bnp with NO plugin.wasm — pure
// declaration the host runs. Classification is by repo shape: a plugin repo
// with no Go source builds codeless; a repo with Go builds wasm as always
// (a converted repo DELETES its Go — that's the point). Both artifact kinds
// may carry blocks/, templates/, and seed/; codeless just has nothing else.

// Declarative artifact dirs shared by both build paths.
const (
	dirBlocks    = "blocks"
	dirTemplates = "templates"
	dirSeed      = "seed"
)

// manifestYAMLName is the optional root-level declarative manifest source for
// codeless plugins (the counterpart of what DESCRIBE captures from Go code).
const manifestYAMLName = "manifest.yaml"

// manifestYAML mirrors the declarative PluginManifest fields a codeless
// plugin can set. File-valued keys are paths relative to the repo root.
type manifestYAML struct {
	ThemePresets      string   `yaml:"theme_presets"`  // JSON file
	BundledFonts      string   `yaml:"bundled_fonts"`  // JSON file
	SettingsSchema    string   `yaml:"settings_schema"` // JSON file
	MasterPages       string   `yaml:"master_pages"`   // JSON file ([]masterPageJSON)
	RequiredIconPacks []string `yaml:"required_icon_packs"`
	CSS               *struct {
		NpmPackages    map[string]string `yaml:"npm_packages"`
		CSSDirectives  []string          `yaml:"css_directives"`
		InputCSSAppend string            `yaml:"input_css_append"`
	} `yaml:"css"`
	Dependencies []struct {
		Plugin     string `yaml:"plugin"`
		MinVersion string `yaml:"min_version"`
		Required   bool   `yaml:"required"`
	} `yaml:"dependencies"`
}

// masterPageJSON mirrors abiv1.MasterPageDefinition for the declarative file.
type masterPageJSON struct {
	Key           string   `json:"key"`
	Title         string   `json:"title"`
	PageTemplates []string `json:"page_templates"`
	Blocks        []struct {
		BlockKey    string         `json:"block_key"`
		Title       string         `json:"title"`
		Content     map[string]any `json:"content"`
		HTMLContent *string        `json:"html_content"`
		Slot        string         `json:"slot"`
		SortOrder   int32          `json:"sort_order"`
	} `json:"blocks"`
}

// blocksYAML is the structural mirror of the CMS blocks.yaml manifest
// (cms blocks.LoadManifest) — a deliberate light duplication, same as the
// Verify↔reader pairing: the packer validates shape and file presence; full
// semantic validation (schema/template/provider checks) runs at install.
type blocksYAML struct {
	Blocks []struct {
		Key          string   `yaml:"key"`
		Title        string   `yaml:"title"`
		Description  string   `yaml:"description"`
		Category     string   `yaml:"category"`
		Schema       string   `yaml:"schema"`
		Template     string   `yaml:"template"`
		SampleData   string   `yaml:"sample_data"`
		Providers    []string `yaml:"providers"`
		RequiredTags []string `yaml:"required_tags"`
		Aliases      []string `yaml:"aliases"`
	} `yaml:"blocks"`
}

// seedJSON is the declarative seed schema (seed/seed.json). Applied by the
// host at load via the WO-WZ-019 provisioner (idempotent).
type seedJSON struct {
	Settings *struct {
		Merge    map[string]any `json:"merge"`
		Override map[string]any `json:"override"`
		Ensure   map[string]any `json:"ensure"`
	} `json:"settings"`
	Media []struct {
		ID     string `json:"id"` // UUID, required (deterministic media key)
		File   string `json:"file"`
		Alt    string `json:"alt"`
		Folder string `json:"folder"`
	} `json:"media"`
	Pages []struct {
		Slug              string `json:"slug"`
		ParentSlug        string `json:"parent_slug"`
		Title             string `json:"title"`
		TemplateKey       string `json:"template_key"`
		ReconcileBlocks   bool   `json:"reconcile_blocks"`
		ReconcileTemplate bool   `json:"reconcile_template"`
		Blocks            []struct {
			BlockKey    string         `json:"block_key"`
			Title       string         `json:"title"`
			Content     map[string]any `json:"content"`
			HTMLContent *string        `json:"html_content"`
			Slot        string         `json:"slot"`
			SortOrder   int32          `json:"sort_order"`
		} `json:"blocks"`
	} `json:"pages"`
	MenuItems []struct {
		Menu      string `json:"menu"`
		Label     string `json:"label"`
		URL       string `json:"url"`
		PageSlug  string `json:"page_slug"`
		SortOrder int32  `json:"sort_order"`
	} `json:"menu_items"`
}

// IsCodelessRepo reports whether dir is a declarative plugin repo: it has a
// plugin.mod but no Go source at the root (the wasm main package's home).
func IsCodelessRepo(dir string) (bool, error) {
	if _, err := os.Stat(filepath.Join(dir, fileMod)); err != nil {
		return false, fmt.Errorf("read plugin.mod (is %s a plugin repo?): %w", dir, err)
	}
	entries, err := os.ReadDir(dir)
	if err != nil {
		return false, err
	}
	for _, e := range entries {
		if !e.IsDir() && strings.HasSuffix(e.Name(), ".go") {
			return false, nil
		}
	}
	return true, nil
}

// BuildCodeless synthesizes manifest.pb from plugin.mod + the declarative
// files and packs a codeless .bnp (no plugin.wasm, no DESCRIBE probe).
func BuildCodeless(_ 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: %w", 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 mod.Plugin.DataDir {
		return nil, fmt.Errorf("codeless plugin cannot request data_dir — there is no code to use it")
	}

	manifest := &abiv1.PluginManifest{
		AbiVersion: hostAbiVersion,
		Name:       mod.Plugin.Name,
		Version:    mod.Plugin.Version,
		Codeless:   true,
	}

	blockCount, err := validateBlocksDir(dir)
	if err != nil {
		return nil, err
	}
	if err := validateSeedDir(dir); err != nil {
		return nil, err
	}
	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)
	}

	entries := []packEntry{
		{ArtifactPath: fileMod, Source: modPath},
		{ArtifactPath: fileManifest, Data: manifestBytes},
	}
	var includedDirs []string
	optional := []struct{ artifact, src string }{
		{dirBlocks, dirBlocks},
		{dirTemplates, dirTemplates},
		{dirSeed, dirSeed},
		{"migrations", "migrations"},
		{"schemas", "schemas"},
		{"assets", "assets"},
	}
	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)
		}
	}

	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)
	}

	return &BuildResult{
		OutputPath:    outPath,
		Name:          manifest.GetName(),
		Version:       manifest.GetVersion(),
		Codeless:      true,
		ManifestBytes: int64(len(manifestBytes)),
		ArtifactBytes: artInfo.Size(),
		UncompBytes:   uncomp,
		BlockCount:    blockCount,
		IncludedDirs:  includedDirs,
	}, nil
}

// validateBlocksDir structurally validates blocks/blocks.yaml when present:
// every entry has key/title/schema/template, referenced files exist within
// blocks/, and schemas are valid JSON. Returns the block count (0 when the
// dir is absent).
func validateBlocksDir(dir string) (int, error) {
	root := filepath.Join(dir, dirBlocks)
	manifestPath := filepath.Join(root, "blocks.yaml")
	if _, err := os.Stat(root); os.IsNotExist(err) {
		return 0, nil
	}
	raw, err := os.ReadFile(manifestPath)
	if err != nil {
		return 0, fmt.Errorf("blocks/ present but blocks.yaml unreadable: %w", err)
	}
	var bf blocksYAML
	if err := yaml.Unmarshal(raw, &bf); err != nil {
		return 0, fmt.Errorf("parse blocks/blocks.yaml: %w", err)
	}
	seen := map[string]bool{}
	for i, b := range bf.Blocks {
		if b.Key == "" {
			return 0, fmt.Errorf("blocks.yaml: entry %d has no key", i)
		}
		if seen[b.Key] {
			return 0, fmt.Errorf("blocks.yaml: duplicate key %q", b.Key)
		}
		seen[b.Key] = true
		if b.Title == "" || b.Schema == "" || b.Template == "" {
			return 0, fmt.Errorf("blocks.yaml: %q must declare title, schema, and template", b.Key)
		}
		for _, f := range []string{b.Schema, b.Template, b.SampleData} {
			if f == "" {
				continue
			}
			if err := fileWithin(root, f); err != nil {
				return 0, fmt.Errorf("blocks.yaml: %q: %w", b.Key, err)
			}
		}
		schemaRaw, err := os.ReadFile(filepath.Join(root, b.Schema))
		if err != nil {
			return 0, fmt.Errorf("blocks.yaml: %q schema: %w", b.Key, err)
		}
		if !json.Valid(schemaRaw) {
			return 0, fmt.Errorf("blocks.yaml: %q schema %s is not valid JSON", b.Key, b.Schema)
		}
	}
	return len(bf.Blocks), nil
}

// validateSeedDir validates seed/seed.json when the dir is present: it
// parses, media entries carry an id + an existing file, pages carry slugs.
func validateSeedDir(dir string) error {
	root := filepath.Join(dir, dirSeed)
	if _, err := os.Stat(root); os.IsNotExist(err) {
		return nil
	}
	raw, err := os.ReadFile(filepath.Join(root, "seed.json"))
	if err != nil {
		return fmt.Errorf("seed/ present but seed.json unreadable: %w", err)
	}
	var sf seedJSON
	if err := json.Unmarshal(raw, &sf); err != nil {
		return fmt.Errorf("parse seed/seed.json: %w", err)
	}
	for i, m := range sf.Media {
		if m.ID == "" || m.File == "" {
			return fmt.Errorf("seed.json: media entry %d needs both id and file", i)
		}
		if err := fileWithin(root, m.File); err != nil {
			return fmt.Errorf("seed.json: media %q: %w", m.ID, err)
		}
	}
	for i, p := range sf.Pages {
		if p.Slug == "" || p.Title == "" {
			return fmt.Errorf("seed.json: page entry %d needs slug and title", i)
		}
	}
	for i, mi := range sf.MenuItems {
		if mi.Menu == "" || mi.Label == "" {
			return fmt.Errorf("seed.json: menu item %d needs menu and label", i)
		}
	}
	return nil
}

// applyManifestYAML folds the optional root manifest.yaml into the manifest.
func applyManifestYAML(dir string, m *abiv1.PluginManifest) error {
	raw, err := os.ReadFile(filepath.Join(dir, manifestYAMLName))
	if os.IsNotExist(err) {
		return nil
	}
	if err != nil {
		return fmt.Errorf("read %s: %w", manifestYAMLName, err)
	}
	var my manifestYAML
	if err := yaml.Unmarshal(raw, &my); err != nil {
		return fmt.Errorf("parse %s: %w", manifestYAMLName, err)
	}

	readJSONFile := func(rel, what string) ([]byte, error) {
		if rel == "" {
			return nil, nil
		}
		if err := fileWithin(dir, rel); err != nil {
			return nil, fmt.Errorf("%s: %s: %w", manifestYAMLName, what, err)
		}
		b, err := os.ReadFile(filepath.Join(dir, rel))
		if err != nil {
			return nil, fmt.Errorf("%s: %s: %w", manifestYAMLName, what, err)
		}
		if !json.Valid(b) {
			return nil, fmt.Errorf("%s: %s %s is not valid JSON", manifestYAMLName, what, rel)
		}
		return b, nil
	}

	if m.ThemePresets, err = readJSONFile(my.ThemePresets, "theme_presets"); err != nil {
		return err
	}
	if m.BundledFonts, err = readJSONFile(my.BundledFonts, "bundled_fonts"); err != nil {
		return err
	}
	if m.SettingsSchema, err = readJSONFile(my.SettingsSchema, "settings_schema"); err != nil {
		return err
	}
	m.RequiredIconPacks = my.RequiredIconPacks
	if my.CSS != nil {
		m.CssManifest = &abiv1.CssManifest{
			NpmPackages:    my.CSS.NpmPackages,
			CssDirectives:  my.CSS.CSSDirectives,
			InputCssAppend: my.CSS.InputCSSAppend,
		}
	}
	for _, d := range my.Dependencies {
		m.Dependencies = append(m.Dependencies, &abiv1.Dependency{
			Plugin: d.Plugin, MinVersion: d.MinVersion, Required: d.Required,
		})
	}

	if my.MasterPages != "" {
		mpRaw, err := readJSONFile(my.MasterPages, "master_pages")
		if err != nil {
			return err
		}
		var mps []masterPageJSON
		if err := json.Unmarshal(mpRaw, &mps); err != nil {
			return fmt.Errorf("%s: master_pages %s: %w", manifestYAMLName, my.MasterPages, err)
		}
		for _, mp := range mps {
			def := &abiv1.MasterPageDefinition{
				Key: mp.Key, Title: mp.Title, PageTemplates: mp.PageTemplates,
			}
			for _, b := range mp.Blocks {
				contentJSON, err := json.Marshal(b.Content)
				if err != nil {
					return fmt.Errorf("master page %q block %q: %w", mp.Key, b.BlockKey, err)
				}
				def.Blocks = append(def.Blocks, &abiv1.MasterPageBlock{
					BlockKey: b.BlockKey, Title: b.Title, ContentJson: contentJSON,
					HtmlContent: b.HTMLContent, Slot: b.Slot, SortOrder: b.SortOrder,
				})
			}
			m.MasterPages = append(m.MasterPages, def)
		}
	}
	return nil
}

// fileWithin ensures rel names an existing regular file inside root (no
// traversal escapes).
func fileWithin(root, rel string) error {
	clean := filepath.Clean(rel)
	if filepath.IsAbs(clean) || strings.HasPrefix(clean, "..") {
		return fmt.Errorf("path %q escapes the plugin directory", rel)
	}
	fi, err := os.Stat(filepath.Join(root, clean))
	if err != nil {
		return fmt.Errorf("referenced file %q: %w", rel, err)
	}
	if !fi.Mode().IsRegular() {
		return fmt.Errorf("referenced path %q is not a regular file", rel)
	}
	return nil
}