/*
Manifest Validation — Validates Volt v2 manifests before execution.

Checks include:
  - Required fields (name, mode)
  - Enum validation for mode, network, landlock, seccomp, writable_layer
  - Resource limit parsing (human-readable: "512M", "2G")
  - Port mapping parsing ("80:80/tcp", "443:443/udp")
  - CAS reference validation ("cas://sha256:<hex>")
  - Kernel path existence for hybrid modes
  - Workload name safety (delegates to validate.WorkloadName)

Provides both strict Validate() and informational DryRun().

Copyright (c) Armored Gates LLC. All rights reserved.
*/
package manifest

import (
	"fmt"
	"os"
	"regexp"
	"strconv"
	"strings"

	"github.com/armoredgate/volt/pkg/validate"
)

// ── Validation Errors ────────────────────────────────────────────────────────

// ValidationError collects one or more field-level errors.
type ValidationError struct {
	Errors []FieldError
}

func (ve *ValidationError) Error() string {
	var b strings.Builder
	b.WriteString("manifest validation failed:\n")
	for _, fe := range ve.Errors {
		fmt.Fprintf(&b, "  [%s] %s\n", fe.Field, fe.Message)
	}
	return b.String()
}

// FieldError records a single validation failure for a specific field.
type FieldError struct {
	Field   string // e.g. "workload.name", "resources.memory_limit"
	Message string
}

// ── Dry Run Report ───────────────────────────────────────────────────────────

// Severity classifies a report finding.
type Severity string

const (
	SeverityError   Severity = "error"
	SeverityWarning Severity = "warning"
	SeverityInfo    Severity = "info"
)

// Finding is a single line item in a DryRun report.
type Finding struct {
	Severity Severity
	Field    string
	Message  string
}

// Report is the output of DryRun. It contains findings at varying severity
// levels and a summary of resolved resource values.
type Report struct {
	Findings []Finding

	// Resolved values (populated during dry run for display)
	ResolvedMemoryLimit int64  // bytes
	ResolvedMemorySoft  int64  // bytes
	ResolvedPortMaps    []PortMapping
}

// HasErrors returns true if any finding is severity error.
func (r *Report) HasErrors() bool {
	for _, f := range r.Findings {
		if f.Severity == SeverityError {
			return true
		}
	}
	return false
}

// PortMapping is the parsed representation of a port string like "80:80/tcp".
type PortMapping struct {
	HostPort      int
	ContainerPort int
	Protocol      string // "tcp" or "udp"
}

// ── Validate ─────────────────────────────────────────────────────────────────

// Validate performs strict validation of a manifest. Returns nil if the
// manifest is valid. Returns a *ValidationError containing all field errors
// otherwise.
func (m *Manifest) Validate() error {
	var errs []FieldError

	// ── workload ─────────────────────────────────────────────────────────

	if m.Workload.Name == "" {
		errs = append(errs, FieldError{
			Field:   "workload.name",
			Message: "required field is empty",
		})
	} else if err := validate.WorkloadName(m.Workload.Name); err != nil {
		errs = append(errs, FieldError{
			Field:   "workload.name",
			Message: err.Error(),
		})
	}

	if m.Workload.Mode == "" {
		errs = append(errs, FieldError{
			Field:   "workload.mode",
			Message: "required field is empty",
		})
	} else if !ValidModes[m.Workload.Mode] {
		errs = append(errs, FieldError{
			Field:   "workload.mode",
			Message: fmt.Sprintf("invalid mode %q (valid: container, hybrid-native, hybrid-kvm, hybrid-emulated)", m.Workload.Mode),
		})
	}

	// ── kernel (hybrid modes only) ───────────────────────────────────────

	if m.NeedsKernel() {
		if m.Kernel.Path != "" {
			if _, err := os.Stat(m.Kernel.Path); err != nil {
				errs = append(errs, FieldError{
					Field:   "kernel.path",
					Message: fmt.Sprintf("kernel not found: %s", m.Kernel.Path),
				})
			}
		}
		// If no path and no version, the kernel manager will use defaults at
		// runtime — that's acceptable. We only error if an explicit path is
		// given and missing.
	}

	// ── security ─────────────────────────────────────────────────────────

	if m.Security.LandlockProfile != "" {
		lp := LandlockProfile(m.Security.LandlockProfile)
		if !ValidLandlockProfiles[lp] {
			// Could be a file path for custom profile — check if it looks like
			// a path (contains / or .)
			if !looksLikePath(m.Security.LandlockProfile) {
				errs = append(errs, FieldError{
					Field:   "security.landlock_profile",
					Message: fmt.Sprintf("invalid profile %q (valid: strict, default, permissive, custom, or a file path)", m.Security.LandlockProfile),
				})
			}
		}
	}

	if m.Security.SeccompProfile != "" {
		validSeccomp := map[string]bool{
			"strict": true, "default": true, "unconfined": true,
		}
		if !validSeccomp[m.Security.SeccompProfile] && !looksLikePath(m.Security.SeccompProfile) {
			errs = append(errs, FieldError{
				Field:   "security.seccomp_profile",
				Message: fmt.Sprintf("invalid profile %q (valid: strict, default, unconfined, or a file path)", m.Security.SeccompProfile),
			})
		}
	}

	if len(m.Security.Capabilities) > 0 {
		for _, cap := range m.Security.Capabilities {
			if !isValidCapability(cap) {
				errs = append(errs, FieldError{
					Field:   "security.capabilities",
					Message: fmt.Sprintf("unknown capability %q", cap),
				})
			}
		}
	}

	// ── resources ────────────────────────────────────────────────────────

	if m.Resources.MemoryLimit != "" {
		if _, err := ParseMemorySize(m.Resources.MemoryLimit); err != nil {
			errs = append(errs, FieldError{
				Field:   "resources.memory_limit",
				Message: err.Error(),
			})
		}
	}
	if m.Resources.MemorySoft != "" {
		if _, err := ParseMemorySize(m.Resources.MemorySoft); err != nil {
			errs = append(errs, FieldError{
				Field:   "resources.memory_soft",
				Message: err.Error(),
			})
		}
	}
	if m.Resources.CPUWeight != 0 {
		if m.Resources.CPUWeight < 1 || m.Resources.CPUWeight > 10000 {
			errs = append(errs, FieldError{
				Field:   "resources.cpu_weight",
				Message: fmt.Sprintf("cpu_weight %d out of range [1, 10000]", m.Resources.CPUWeight),
			})
		}
	}
	if m.Resources.CPUSet != "" {
		if err := validateCPUSet(m.Resources.CPUSet); err != nil {
			errs = append(errs, FieldError{
				Field:   "resources.cpu_set",
				Message: err.Error(),
			})
		}
	}
	if m.Resources.IOWeight != 0 {
		if m.Resources.IOWeight < 1 || m.Resources.IOWeight > 10000 {
			errs = append(errs, FieldError{
				Field:   "resources.io_weight",
				Message: fmt.Sprintf("io_weight %d out of range [1, 10000]", m.Resources.IOWeight),
			})
		}
	}
	if m.Resources.PidsMax != 0 {
		if m.Resources.PidsMax < 1 {
			errs = append(errs, FieldError{
				Field:   "resources.pids_max",
				Message: "pids_max must be positive",
			})
		}
	}

	// ── network ──────────────────────────────────────────────────────────

	if m.Network.Mode != "" && !ValidNetworkModes[m.Network.Mode] {
		errs = append(errs, FieldError{
			Field:   "network.mode",
			Message: fmt.Sprintf("invalid network mode %q (valid: bridge, host, none, custom)", m.Network.Mode),
		})
	}

	for i, port := range m.Network.Ports {
		if _, err := ParsePortMapping(port); err != nil {
			errs = append(errs, FieldError{
				Field:   fmt.Sprintf("network.ports[%d]", i),
				Message: err.Error(),
			})
		}
	}

	// ── storage ──────────────────────────────────────────────────────────

	if m.Storage.Rootfs != "" && m.HasCASRootfs() {
		if err := validateCASRef(m.Storage.Rootfs); err != nil {
			errs = append(errs, FieldError{
				Field:   "storage.rootfs",
				Message: err.Error(),
			})
		}
	}

	if m.Storage.WritableLayer != "" && !ValidWritableLayerModes[m.Storage.WritableLayer] {
		errs = append(errs, FieldError{
			Field:   "storage.writable_layer",
			Message: fmt.Sprintf("invalid writable_layer %q (valid: overlay, tmpfs, none)", m.Storage.WritableLayer),
		})
	}

	for i, vol := range m.Storage.Volumes {
		if vol.Host == "" {
			errs = append(errs, FieldError{
				Field:   fmt.Sprintf("storage.volumes[%d].host", i),
				Message: "host path is required",
			})
		}
		if vol.Container == "" {
			errs = append(errs, FieldError{
				Field:   fmt.Sprintf("storage.volumes[%d].container", i),
				Message: "container path is required",
			})
		}
	}

	if len(errs) > 0 {
		return &ValidationError{Errors: errs}
	}
	return nil
}

// ── DryRun ───────────────────────────────────────────────────────────────────

// DryRun performs validation and additionally resolves human-readable resource
// values into machine values, returning a Report with findings and resolved
// values. Unlike Validate(), DryRun never returns an error — the Report itself
// carries severity information.
func (m *Manifest) DryRun() *Report {
	r := &Report{}

	// Run validation and collect errors as findings.
	if err := m.Validate(); err != nil {
		if ve, ok := err.(*ValidationError); ok {
			for _, fe := range ve.Errors {
				r.Findings = append(r.Findings, Finding{
					Severity: SeverityError,
					Field:    fe.Field,
					Message:  fe.Message,
				})
			}
		}
	}

	// ── Informational findings ───────────────────────────────────────────

	// Resolve memory limits.
	if m.Resources.MemoryLimit != "" {
		if bytes, err := ParseMemorySize(m.Resources.MemoryLimit); err == nil {
			r.ResolvedMemoryLimit = bytes
			r.Findings = append(r.Findings, Finding{
				Severity: SeverityInfo,
				Field:    "resources.memory_limit",
				Message:  fmt.Sprintf("resolved to %d bytes (%s)", bytes, m.Resources.MemoryLimit),
			})
		}
	} else {
		r.Findings = append(r.Findings, Finding{
			Severity: SeverityWarning,
			Field:    "resources.memory_limit",
			Message:  "not set — workload will have no memory limit",
		})
	}

	if m.Resources.MemorySoft != "" {
		if bytes, err := ParseMemorySize(m.Resources.MemorySoft); err == nil {
			r.ResolvedMemorySoft = bytes
		}
	}

	// Resolve port mappings.
	for _, port := range m.Network.Ports {
		if pm, err := ParsePortMapping(port); err == nil {
			r.ResolvedPortMaps = append(r.ResolvedPortMaps, pm)
		}
	}

	// Warn about container mode with kernel section.
	if m.Workload.Mode == ModeContainer && (m.Kernel.Path != "" || m.Kernel.Version != "") {
		r.Findings = append(r.Findings, Finding{
			Severity: SeverityWarning,
			Field:    "kernel",
			Message:  "kernel section is set but mode is 'container' — kernel config will be ignored",
		})
	}

	// Warn about hybrid modes without kernel section.
	if m.NeedsKernel() && m.Kernel.Path == "" && m.Kernel.Version == "" {
		r.Findings = append(r.Findings, Finding{
			Severity: SeverityWarning,
			Field:    "kernel",
			Message:  "hybrid mode selected but no kernel specified — will use host default",
		})
	}

	// Check soft < hard memory.
	if r.ResolvedMemoryLimit > 0 && r.ResolvedMemorySoft > 0 {
		if r.ResolvedMemorySoft > r.ResolvedMemoryLimit {
			r.Findings = append(r.Findings, Finding{
				Severity: SeverityWarning,
				Field:    "resources.memory_soft",
				Message:  "memory_soft exceeds memory_limit — soft limit will have no effect",
			})
		}
	}

	// Info about writable layer.
	if m.Storage.WritableLayer == WritableNone {
		r.Findings = append(r.Findings, Finding{
			Severity: SeverityInfo,
			Field:    "storage.writable_layer",
			Message:  "writable_layer is 'none' — rootfs will be completely read-only",
		})
	}

	return r
}

// ── Parsers ──────────────────────────────────────────────────────────────────

// ParseMemorySize parses a human-readable memory size string into bytes.
// Supports: "512M", "2G", "1024K", "1T", "256m", "100" (raw bytes).
func ParseMemorySize(s string) (int64, error) {
	s = strings.TrimSpace(s)
	if s == "" {
		return 0, fmt.Errorf("empty memory size")
	}

	// Raw integer (bytes).
	if n, err := strconv.ParseInt(s, 10, 64); err == nil {
		return n, nil
	}

	// Strip unit suffix.
	upper := strings.ToUpper(s)
	var multiplier int64 = 1
	var numStr string

	switch {
	case strings.HasSuffix(upper, "T"):
		multiplier = 1024 * 1024 * 1024 * 1024
		numStr = s[:len(s)-1]
	case strings.HasSuffix(upper, "G"):
		multiplier = 1024 * 1024 * 1024
		numStr = s[:len(s)-1]
	case strings.HasSuffix(upper, "M"):
		multiplier = 1024 * 1024
		numStr = s[:len(s)-1]
	case strings.HasSuffix(upper, "K"):
		multiplier = 1024
		numStr = s[:len(s)-1]
	default:
		return 0, fmt.Errorf("invalid memory size %q: expected a number with optional suffix K/M/G/T", s)
	}

	n, err := strconv.ParseFloat(strings.TrimSpace(numStr), 64)
	if err != nil {
		return 0, fmt.Errorf("invalid memory size %q: %w", s, err)
	}
	if n < 0 {
		return 0, fmt.Errorf("invalid memory size %q: negative value", s)
	}

	return int64(n * float64(multiplier)), nil
}

// portRegex matches "hostPort:containerPort/protocol" or "hostPort:containerPort".
var portRegex = regexp.MustCompile(`^(\d+):(\d+)(?:/(tcp|udp))?$`)

// ParsePortMapping parses a port mapping string like "80:80/tcp".
func ParsePortMapping(s string) (PortMapping, error) {
	s = strings.TrimSpace(s)
	matches := portRegex.FindStringSubmatch(s)
	if matches == nil {
		return PortMapping{}, fmt.Errorf("invalid port mapping %q: expected hostPort:containerPort[/tcp|udp]", s)
	}

	hostPort, _ := strconv.Atoi(matches[1])
	containerPort, _ := strconv.Atoi(matches[2])
	proto := matches[3]
	if proto == "" {
		proto = "tcp"
	}

	if hostPort < 1 || hostPort > 65535 {
		return PortMapping{}, fmt.Errorf("invalid host port %d: must be 1-65535", hostPort)
	}
	if containerPort < 1 || containerPort > 65535 {
		return PortMapping{}, fmt.Errorf("invalid container port %d: must be 1-65535", containerPort)
	}

	return PortMapping{
		HostPort:      hostPort,
		ContainerPort: containerPort,
		Protocol:      proto,
	}, nil
}

// ── Internal Helpers ─────────────────────────────────────────────────────────

// casRefRegex matches "cas://sha256:<hex>" or "cas://sha512:<hex>".
var casRefRegex = regexp.MustCompile(`^cas://(sha256|sha512):([0-9a-fA-F]+)$`)

// validateCASRef validates a CAS reference string.
func validateCASRef(ref string) error {
	if !casRefRegex.MatchString(ref) {
		return fmt.Errorf("invalid CAS reference %q: expected cas://sha256:<hex> or cas://sha512:<hex>", ref)
	}
	return nil
}

// cpuSetRegex matches ranges like "0-3", "0,1,2,3", "0-3,8-11".
var cpuSetRegex = regexp.MustCompile(`^(\d+(-\d+)?)(,\d+(-\d+)?)*$`)

// validateCPUSet validates a cpuset string.
func validateCPUSet(s string) error {
	if !cpuSetRegex.MatchString(s) {
		return fmt.Errorf("invalid cpu_set %q: expected ranges like '0-3' or '0,1,2,3'", s)
	}
	// Verify ranges are valid (start <= end).
	for _, part := range strings.Split(s, ",") {
		if strings.Contains(part, "-") {
			bounds := strings.SplitN(part, "-", 2)
			start, _ := strconv.Atoi(bounds[0])
			end, _ := strconv.Atoi(bounds[1])
			if start > end {
				return fmt.Errorf("invalid cpu_set range %q: start (%d) > end (%d)", part, start, end)
			}
		}
	}
	return nil
}

// looksLikePath returns true if s looks like a filesystem path.
func looksLikePath(s string) bool {
	return strings.Contains(s, "/") || strings.Contains(s, ".")
}

// knownCapabilities is the set of recognized Linux capabilities (without the
// CAP_ prefix for convenience).
var knownCapabilities = map[string]bool{
	"AUDIT_CONTROL":      true,
	"AUDIT_READ":         true,
	"AUDIT_WRITE":        true,
	"BLOCK_SUSPEND":      true,
	"BPF":                true,
	"CHECKPOINT_RESTORE": true,
	"CHOWN":              true,
	"DAC_OVERRIDE":       true,
	"DAC_READ_SEARCH":    true,
	"FOWNER":             true,
	"FSETID":             true,
	"IPC_LOCK":           true,
	"IPC_OWNER":          true,
	"KILL":               true,
	"LEASE":              true,
	"LINUX_IMMUTABLE":    true,
	"MAC_ADMIN":          true,
	"MAC_OVERRIDE":       true,
	"MKNOD":              true,
	"NET_ADMIN":          true,
	"NET_BIND_SERVICE":   true,
	"NET_BROADCAST":      true,
	"NET_RAW":            true,
	"PERFMON":            true,
	"SETFCAP":            true,
	"SETGID":             true,
	"SETPCAP":            true,
	"SETUID":             true,
	"SYSLOG":             true,
	"SYS_ADMIN":          true,
	"SYS_BOOT":           true,
	"SYS_CHROOT":         true,
	"SYS_MODULE":         true,
	"SYS_NICE":           true,
	"SYS_PACCT":          true,
	"SYS_PTRACE":         true,
	"SYS_RAWIO":          true,
	"SYS_RESOURCE":       true,
	"SYS_TIME":           true,
	"SYS_TTY_CONFIG":     true,
	"WAKE_ALARM":         true,
}

// isValidCapability checks if a capability name is recognized.
// Accepts with or without "CAP_" prefix.
func isValidCapability(name string) bool {
	upper := strings.ToUpper(strings.TrimPrefix(name, "CAP_"))
	return knownCapabilities[upper]
}