package volume

import (
	"encoding/json"
	"fmt"
	"path/filepath"
	"regexp"
	"strings"

	"github.com/alexei/tinyforge/internal/store"
)

// resolveAbsolute validates that the source path is under one of the allowed prefixes.
func resolveAbsolute(source, allowedPathsJSON string) (string, error) {
	if source == "" {
		return "", fmt.Errorf("absolute scope requires a source path")
	}

	cleaned := filepath.Clean(source)
	if !filepath.IsAbs(cleaned) {
		return "", fmt.Errorf("absolute scope requires an absolute source path (starting with /)")
	}

	allowed, err := parseAllowedPaths(allowedPathsJSON)
	if err != nil {
		return "", fmt.Errorf("failed to parse allowed volume paths: %w", err)
	}
	if len(allowed) == 0 {
		return "", fmt.Errorf("absolute volume paths are disabled (no allowed paths configured in settings)")
	}

	for _, prefix := range allowed {
		prefixClean := filepath.Clean(prefix)
		if strings.HasPrefix(cleaned, prefixClean+string(filepath.Separator)) || cleaned == prefixClean {
			return cleaned, nil
		}
	}

	return "", fmt.Errorf("path %q is not under any allowed volume path", source)
}

// parseAllowedPaths parses a JSON array of path strings.
func parseAllowedPaths(jsonStr string) ([]string, error) {
	if jsonStr == "" || jsonStr == "[]" {
		return nil, nil
	}
	var paths []string
	if err := json.Unmarshal([]byte(jsonStr), &paths); err != nil {
		return nil, err
	}
	return paths, nil
}

// ParseAllowedPaths is the exported version for use in API validation.
func ParseAllowedPaths(jsonStr string) ([]string, error) {
	return parseAllowedPaths(jsonStr)
}

// ResolveWorkloadParams holds the parameters needed to resolve a
// workload-volume's host path. Unlike ResolveParams it is keyed on the
// workload identity (name + id) rather than the legacy project/stage
// dual-key, so it survives the Workload-first cutover.
type ResolveWorkloadParams struct {
	BasePath           string
	WorkloadID         string
	WorkloadName       string
	ImageTag           string // required for "instance" scope only
	AllowedVolumePaths string // JSON array of allowed absolute paths
}

// ResolveWorkloadPath returns the absolute host path for a WorkloadVolume.
// Scope semantics map onto the workload-first model:
//
//   - absolute   — host bind, must lie under settings.AllowedVolumePaths.
//   - ephemeral  — caller renders this as tmpfs; the function returns an
//     error because there is no host path.
//   - instance   — per-tag isolation under <workload>/instance-<tag>/<source>.
//     Useful for blue-green when each running instance needs its own dir.
//   - stage, project — both legacy names collapse to "shared across all
//     instances of this workload" under <workload>/<source>. Two names
//     for one shape is intentional: it lets legacy data migrate without
//     a path rewrite.
//   - project_named — workload-scoped named volume under
//     <workload>/_named/<name>/<source>.
//   - named         — globally-scoped named volume under
//     _named/<name>/<source>.
//
// The <workload> directory segment is `<sanitized-name>-<short-id>`. The
// short-id suffix prevents collisions when two workloads share a name
// (the workloads table only enforces uniqueness on (kind, ref_id)).
func ResolveWorkloadPath(vol store.WorkloadVolume, params ResolveWorkloadParams) (string, error) {
	scope := vol.Scope
	if scope == "" {
		return "", fmt.Errorf("workload volume: scope is required")
	}
	if scope == string(store.VolumeScopeEphemeral) {
		return "", fmt.Errorf("ephemeral volumes have no host path")
	}
	if scope == string(store.VolumeScopeAbsolute) {
		return resolveAbsolute(vol.Source, params.AllowedVolumePaths)
	}
	if params.BasePath == "" {
		return "", fmt.Errorf("workload volume: base path is required for scope %q", scope)
	}

	workloadDir, err := workloadPathSegment(params.WorkloadName, params.WorkloadID)
	if err != nil {
		return "", err
	}

	switch scope {
	case string(store.VolumeScopeInstance):
		if params.ImageTag == "" {
			return "", fmt.Errorf("instance scope requires image tag")
		}
		tag := sanitizePathSegment(params.ImageTag)
		if tag == "" {
			return "", fmt.Errorf("instance scope requires non-empty image tag")
		}
		return filepath.Join(params.BasePath, workloadDir, "instance-"+tag, vol.Source), nil
	case string(store.VolumeScopeStage), string(store.VolumeScopeProject):
		return filepath.Join(params.BasePath, workloadDir, vol.Source), nil
	case string(store.VolumeScopeProjectNamed):
		name := sanitizePathSegment(vol.Name)
		if name == "" {
			return "", fmt.Errorf("project_named scope requires name")
		}
		return filepath.Join(params.BasePath, workloadDir, "_named", name, vol.Source), nil
	case string(store.VolumeScopeNamed):
		name := sanitizePathSegment(vol.Name)
		if name == "" {
			return "", fmt.Errorf("named scope requires name")
		}
		return filepath.Join(params.BasePath, "_named", name, vol.Source), nil
	default:
		return "", fmt.Errorf("unknown volume scope %q", scope)
	}
}

// pathSegmentSanitizer collapses anything outside the [a-zA-Z0-9_.-] set
// to a single dash. The character set matches Docker's permissive segment
// rules; the additional Trim afterward keeps the segment from starting
// or ending with a separator.
var pathSegmentSanitizer = regexp.MustCompile(`[^a-zA-Z0-9_.-]+`)

func sanitizePathSegment(s string) string {
	s = strings.TrimSpace(s)
	if s == "" {
		return ""
	}
	return strings.Trim(pathSegmentSanitizer.ReplaceAllString(s, "-"), "-")
}

// workloadPathSegment builds the per-workload directory name. The
// 8-char id-short suffix disambiguates same-named workloads — only
// (kind, ref_id) is unique at the DB level, so names alone are unsafe.
// Returns an error when both identity fields are empty, since the
// resulting path would not be workload-scoped.
func workloadPathSegment(name, id string) (string, error) {
	cleanName := sanitizePathSegment(name)
	idShort := id
	if len(idShort) > 8 {
		idShort = idShort[:8]
	}
	idShort = sanitizePathSegment(idShort)
	if cleanName == "" && idShort == "" {
		return "", fmt.Errorf("workload volume: workload id or name required")
	}
	if cleanName == "" {
		return idShort, nil
	}
	if idShort == "" {
		return cleanName, nil
	}
	return cleanName + "-" + idShort, nil
}