// SPDX-License-Identifier: GPL-3.0-or-later

package detectors

import (
	"fmt"
	"strings"

	"codeberg.org/anassaeneroi/enodia-sentinal/go-agent/internal/config"
	"codeberg.org/anassaeneroi/enodia-sentinal/go-agent/internal/model"
)

const (
	SIDMemoryObfuscation       = 100039
	SIDProcessHidingLibrary    = 100048
	SIDProcessInjectionLibrary = 100049
)

var memoryWritablePrefixes = []string{"/tmp/", "/dev/shm/", "/var/tmp/", "/run/user/"}
var memoryLibraryExtensions = []string{".so", ".so.", ".dylib"}
var memoryHideHints = []string{
	"libhide", "libprocesshide", "process_hide", "proc_hide", "rootkit_hide",
}

// MemoryObfuscation ports the /proc/<pid>/maps detector. It reports one alert
// per signature and process, preserving Python's useful signal compression
// when a process has many suspicious mappings of the same kind.
func MemoryObfuscation(state model.State, cfg config.Config) []model.Alert {
	alerts := make([]model.Alert, 0)
	for _, process := range state.Processes {
		comm := process.Comm
		if comm == "" {
			comm = "?"
		}
		seen := map[string]bool{}
		for _, memory := range process.MemoryMaps {
			signature, severity, detail := memoryIndicator(memory, cfg)
			if signature == "" || seen[signature] {
				continue
			}
			// JIT allowlisting applies only to generic executable memory. A
			// library whose name suggests hiding or injection stays reviewable.
			if signature == "memory_obfuscation" && cfg.MemoryObfuscationAllowComms[comm] {
				continue
			}
			seen[signature] = true
			sid, classtype := SIDMemoryObfuscation, "memory-obfuscation"
			if signature == "process_hiding_library" {
				sid, classtype = SIDProcessHidingLibrary, "process-hiding"
			} else if signature == "process_injection_library" {
				sid, classtype = SIDProcessInjectionLibrary, "process-injection"
			}
			alerts = append(alerts, model.Alert{
				SID: sid, Severity: severity, Signature: signature,
				Classtype: classtype,
				Key:       fmt.Sprintf("mem:%s:%d:%x-%x", signature, process.PID, memory.Start, memory.End),
				Detail: fmt.Sprintf("pid=%d comm=%s %s range=%x-%x",
					process.PID, comm, detail, memory.Start, memory.End),
				PIDs: []int{process.PID},
			})
		}
	}
	return alerts
}

func memoryIndicator(memory model.MemoryMap, cfg config.Config) (string, string, string) {
	path := memory.Path
	if pathAllowed(path, cfg.MemoryObfuscationAllowPaths) {
		return "", "MEDIUM", ""
	}
	if path != "" && hasMemoryHint(path) {
		return "process_hiding_library", "CRITICAL",
			fmt.Sprintf("mapped library name suggests process hiding: %s", path)
	}
	executable := strings.Contains(memory.Perms, "x")
	writable := strings.Contains(memory.Perms, "w")
	if executable && path != "" && writableLibrary(path) {
		return "process_injection_library", "HIGH",
			fmt.Sprintf("executable library mapped from writable/runtime path: %s", path)
	}
	if executable && (strings.Contains(path, "memfd:") || strings.Contains(path, "(deleted)")) {
		return "memory_obfuscation", "CRITICAL",
			fmt.Sprintf("executable transient mapping perms=%s path=%s", memory.Perms, displayPath(path))
	}
	if executable && writable {
		return "memory_obfuscation", "HIGH",
			fmt.Sprintf("writable+executable memory mapping perms=%s path=%s", memory.Perms, displayPath(path))
	}
	if executable && anonymousPath(path) {
		return "memory_obfuscation", "HIGH",
			fmt.Sprintf("executable anonymous memory mapping perms=%s path=%s", memory.Perms, displayPath(path))
	}
	return "", "MEDIUM", ""
}

func pathAllowed(path string, prefixes []string) bool {
	for _, prefix := range prefixes {
		if prefix != "" && strings.HasPrefix(path, prefix) {
			return true
		}
	}
	return false
}

func hasMemoryHint(path string) bool {
	name := path
	if index := strings.LastIndex(name, "/"); index >= 0 {
		name = name[index+1:]
	}
	name = strings.ToLower(name)
	for _, hint := range memoryHideHints {
		if strings.Contains(name, hint) {
			return true
		}
	}
	return false
}

func writableLibrary(path string) bool {
	lower := strings.ToLower(path)
	allowedPrefix := false
	for _, prefix := range memoryWritablePrefixes {
		if strings.HasPrefix(lower, prefix) {
			allowedPrefix = true
			break
		}
	}
	if !allowedPrefix {
		return false
	}
	name := lower
	if index := strings.LastIndex(name, "/"); index >= 0 {
		name = name[index+1:]
	}
	for _, extension := range memoryLibraryExtensions {
		if strings.Contains(name, extension) {
			return true
		}
	}
	return false
}

func anonymousPath(path string) bool {
	return path == "" || path == "[heap]" || path == "[stack]" ||
		strings.HasPrefix(path, "[anon") || strings.HasPrefix(path, "[stack:")
}

func displayPath(path string) string {
	if path != "" {
		return path
	}
	return "<anonymous>"
}