package execenv

import (
	"fmt"
	"log/slog"
	"os"
	"regexp"
	"runtime"
	"strconv"
	"strings"

	"github.com/pelletier/go-toml/v2"
)

// Background
//
// On macOS, Codex's Seatbelt sandbox in the `workspace-write` mode silently
// ignores `[sandbox_workspace_write] network_access = true`. DNS resolution is
// blocked at the syscall layer, so processes inside the sandbox see
// `no such host` errors when calling out (for example, `multica issue get`
// hitting the Multica API). See upstream issue openai/codex#10390.
//
// Until a fixed Codex release ships, the per-task Codex config on macOS needs
// to fall back to `sandbox_mode = "danger-full-access"` so the agent can
// actually reach the Multica API. On Linux (and on macOS once the upstream
// fix is released), the normal `workspace-write` + `network_access = true`
// combo is preferred because it keeps the filesystem sandbox intact.
//
// CodexDarwinNetworkAccessFixedVersion is the earliest Codex CLI version in
// which `network_access = true` is honored under Seatbelt on macOS. Bump this
// constant when the upstream fix ships. Empty string means "no known fixed
// release yet — always treat macOS Codex as broken for network access".
const CodexDarwinNetworkAccessFixedVersion = ""

// codexSandboxPolicy describes how the per-task Codex config.toml should
// configure the sandbox.
type codexSandboxPolicy struct {
	// Mode is the value written as `sandbox_mode = "..."`.
	Mode string
	// NetworkAccess controls `[sandbox_workspace_write] network_access`.
	// Only meaningful when Mode is "workspace-write".
	NetworkAccess bool
	// WritableRoots are extra absolute paths added to
	// `[sandbox_workspace_write] writable_roots`, granting write access outside
	// the sandbox cwd (the task workdir). Under workspace-write (Linux Landlock)
	// everything outside the cwd is read-only, which breaks tools that write to
	// $HOME (npm, Prisma). The daemon points this at the per-task writable HOME.
	// Only emitted when Mode is "workspace-write"; empty on darwin
	// danger-full-access, where the filesystem is not sandboxed at all. See
	// task_home.go.
	WritableRoots []string
	// Reason is a short human-readable label used in warn-level logs.
	Reason string
	// Hint is an optional, actionable remediation surfaced in warn-level logs
	// when Mode is danger-full-access. It is empty when there is no generic
	// action to surface (e.g. the Windows compatibility fallback, where
	// enabling Codex's native sandbox is deferred follow-up work rather than a
	// version bump), so the log omits the hint instead of showing an irrelevant
	// one.
	Hint string
}

// resolveGOOS returns goos, or runtime.GOOS when goos is empty. Callers pass an
// explicit goos in tests; production leaves it empty to use the host platform.
func resolveGOOS(goos string) string {
	if goos == "" {
		return runtime.GOOS
	}
	return goos
}

// codexSandboxPolicyFor picks the default policy for the given platform and
// detected Codex CLI version. It is the platform baseline; per-task user config
// can refine it (see codexSandboxPolicyForConfig).
//
//   - Linux: workspace-write with network access. Landlock enforces the
//     filesystem sandbox and is not affected by the macOS Seatbelt bug.
//   - Windows: danger-full-access, as a deliberate compatibility choice.
//     Codex ships a native Windows sandbox (windows.sandbox = "unelevated" via
//     a Restricted Token, or "elevated"), but it is still experimental with
//     known reliability limitations, so the daemon does not enable it by
//     default. When no native windows.sandbox is configured, Codex cannot
//     enforce workspace-write on Windows (it downgrades to read-only) and then
//     rejects non-safe mutation commands "by policy" — e.g. `multica issue
//     create` fails — because under approval_policy = "never" the request never
//     reaches the daemon's auto-approver. danger-full-access sidesteps that.
//     Enabling the native sandbox is tracked as separate follow-up work. See
//     MUL-4957. A user who has opted into windows.sandbox (via config.toml or a
//     `-c` custom arg) keeps workspace-write instead of this fallback, and an
//     undecidable config fails closed; that logic lives in
//     codexSandboxPolicyForConfig / resolveWindowsSandboxState.
//   - darwin with a version at or above CodexDarwinNetworkAccessFixedVersion:
//     workspace-write with network access (upstream bug fixed).
//   - darwin otherwise (including when the version is unknown): fall back to
//     danger-full-access so the Multica CLI can reach the API.
func codexSandboxPolicyFor(goos, detectedVersion string) codexSandboxPolicy {
	if goos == "" {
		goos = runtime.GOOS
	}
	if goos == "windows" {
		return codexSandboxPolicy{
			Mode:   "danger-full-access",
			Reason: "codex on windows: compatibility fallback; no native windows.sandbox configured, so workspace-write cannot be enforced (MUL-4957)",
		}
	}
	if goos != "darwin" {
		return codexSandboxPolicy{
			Mode:          "workspace-write",
			NetworkAccess: true,
			Reason:        "non-darwin platform — seatbelt bug does not apply",
		}
	}
	if codexDarwinNetworkAccessFixed(detectedVersion) {
		return codexSandboxPolicy{
			Mode:          "workspace-write",
			NetworkAccess: true,
			Reason:        "codex version includes macOS network_access fix",
		}
	}
	reason := "codex on macOS: seatbelt ignores sandbox_workspace_write.network_access (openai/codex#10390)"
	if detectedVersion == "" {
		reason += " — version unknown, assuming broken"
	}
	return codexSandboxPolicy{
		Mode:          "danger-full-access",
		NetworkAccess: false,
		Reason:        reason,
		Hint:          codexUpgradeHint(),
	}
}

// windowsSandboxConfig is the tri-state of a native Codex Windows sandbox
// selection. It is three-valued (not a bool) so an undecidable config fails
// closed — the daemon never loosens to danger-full-access when it cannot
// confirm the user's intent. See MUL-4957.
type windowsSandboxConfig int

const (
	// windowsSandboxAbsent: confidently no native sandbox is selected anywhere,
	// so the danger-full-access compatibility fallback is safe to apply.
	windowsSandboxAbsent windowsSandboxConfig = iota
	// windowsSandboxNative: a valid windows.sandbox = "unelevated"|"elevated"
	// is selected, so keep workspace-write and let Codex enforce isolation.
	windowsSandboxNative
	// windowsSandboxUndecidable: the config could not be read/parsed, or holds
	// a windows.sandbox value Codex does not accept. The daemon cannot tell
	// whether the user asked for isolation, so it must NOT loosen — fail closed.
	windowsSandboxUndecidable
)

// codexSandboxPolicyForConfig returns the platform default from
// codexSandboxPolicyFor for linux/darwin. On Windows it applies the resolved
// native-sandbox state (see resolveWindowsSandboxState): a user who opted into
// windows.sandbox keeps workspace-write, an undecidable config fails closed to
// workspace-write, and only a confidently absent sandbox gets the
// danger-full-access compatibility fallback. See MUL-4957.
//
// This is intentionally the branch point for the eventual native-sandbox
// rollout: flipping the Windows default later means writing windows.sandbox
// ourselves and defaulting winState to native, not restructuring callers.
func codexSandboxPolicyForConfig(goos, detectedVersion string, winState windowsSandboxConfig) codexSandboxPolicy {
	if goos == "" {
		goos = runtime.GOOS
	}
	if goos == "windows" {
		return codexSandboxPolicyForWindows(winState)
	}
	return codexSandboxPolicyFor(goos, detectedVersion)
}

// codexSandboxPolicyForWindows maps a resolved native-sandbox state to a
// policy. Native and Undecidable both keep workspace-write (Undecidable is the
// fail-closed case — it never loosens on doubt); only a confidently absent
// native sandbox gets the danger-full-access compatibility fallback.
func codexSandboxPolicyForWindows(state windowsSandboxConfig) codexSandboxPolicy {
	switch state {
	case windowsSandboxNative:
		return codexSandboxPolicy{
			Mode:          "workspace-write",
			NetworkAccess: true,
			Reason:        "codex on windows: native windows.sandbox configured; keeping workspace-write so Codex enforces task isolation",
		}
	case windowsSandboxUndecidable:
		return codexSandboxPolicy{
			Mode:          "workspace-write",
			NetworkAccess: true,
			Reason:        "codex on windows: windows.sandbox config undecidable (unreadable/unparseable/invalid); failing closed to workspace-write rather than loosening (MUL-4957)",
		}
	default: // windowsSandboxAbsent
		return codexSandboxPolicy{
			Mode:   "danger-full-access",
			Reason: "codex on windows: compatibility fallback; no native windows.sandbox configured (MUL-4957)",
		}
	}
}

// windowsSandboxFromConfig classifies the windows.sandbox selection in a
// config.toml body. Codex accepts only the exact-lowercase variants
// "unelevated"/"elevated" and refuses to load a config with any other value, so
// anything else present is treated as undecidable (fail closed) rather than a
// safe "absent". Unparseable TOML is likewise undecidable — Codex would reject
// the same file. An absent windows.sandbox key is a genuine "absent".
func windowsSandboxFromConfig(config string) windowsSandboxConfig {
	var probe struct {
		Windows struct {
			Sandbox string `toml:"sandbox"`
		} `toml:"windows"`
	}
	if err := toml.Unmarshal([]byte(config), &probe); err != nil {
		return windowsSandboxUndecidable
	}
	return classifyWindowsSandboxValue(probe.Windows.Sandbox)
}

// codexConfigOverrideValueRe matches the value token of a Codex `-c` /
// `--config` windows.sandbox override, e.g. `windows.sandbox = "unelevated"`.
// It tolerates whitespace around the dotted key and the `=`, matching Codex's
// own lenient `-c` parsing.
var codexWindowsSandboxOverrideRe = regexp.MustCompile(`^\s*windows\s*\.\s*sandbox\s*=`)

// windowsSandboxFromCustomArgs classifies a native Windows sandbox selection
// passed via Codex `-c windows.sandbox=...` / `--config windows.sandbox=...`
// args. These never land in config.toml (they stay in argv and are applied on
// top of it), so config-only detection would miss them — the MUL-4957 review's
// second must-fix. Mirrors the override-parsing shape in server/pkg/agent's
// buildCodexArgs: inline (`-c=windows.sandbox=x`) and two-token
// (`-c windows.sandbox=x`) forms, last occurrence winning (Codex is last-wins).
func windowsSandboxFromCustomArgs(args []string) windowsSandboxConfig {
	state := windowsSandboxAbsent
	for i := 0; i < len(args); i++ {
		arg := args[i]
		flag := arg
		value := ""
		hasInlineValue := false
		if idx := strings.Index(arg, "="); idx > 0 {
			flag = arg[:idx]
			value = arg[idx+1:]
			hasInlineValue = true
		}
		if flag != "-c" && flag != "--config" {
			continue
		}
		if !hasInlineValue {
			if i+1 >= len(args) {
				continue
			}
			i++
			value = args[i]
		}
		if !codexWindowsSandboxOverrideRe.MatchString(value) {
			continue
		}
		// A windows.sandbox override token: take the part after its first `=`.
		if eq := strings.Index(value, "="); eq >= 0 {
			state = classifyWindowsSandboxValue(value[eq+1:])
		}
	}
	return state
}

// classifyWindowsSandboxValue maps a raw windows.sandbox value (from config.toml
// or a `-c` arg, possibly surrounded by whitespace/quotes) to a tri-state. Only
// the exact-lowercase variants Codex accepts count as native; a present but
// unaccepted value is undecidable (Codex would refuse the config); an empty
// value is absent.
func classifyWindowsSandboxValue(raw string) windowsSandboxConfig {
	v := strings.TrimSpace(raw)
	v = strings.Trim(v, `"'`)
	v = strings.TrimSpace(v)
	switch v {
	case "":
		return windowsSandboxAbsent
	case "unelevated", "elevated":
		return windowsSandboxNative
	default:
		return windowsSandboxUndecidable
	}
}

// resolveWindowsSandbox folds per-layer states into one. Undecidable wins over
// everything (any broken/ambiguous layer means fail closed), then Native over
// Absent (an opt-in in any layer keeps isolation).
func resolveWindowsSandbox(states ...windowsSandboxConfig) windowsSandboxConfig {
	result := windowsSandboxAbsent
	for _, s := range states {
		if s == windowsSandboxUndecidable {
			return windowsSandboxUndecidable
		}
		if s == windowsSandboxNative {
			result = windowsSandboxNative
		}
	}
	return result
}

// codexDarwinNetworkAccessFixed returns true if the given detected version is
// known to honor `network_access = true` under Seatbelt on macOS.
func codexDarwinNetworkAccessFixed(detectedVersion string) bool {
	if CodexDarwinNetworkAccessFixedVersion == "" || detectedVersion == "" {
		return false
	}
	fixed, err := parseCodexSemver(CodexDarwinNetworkAccessFixedVersion)
	if err != nil {
		return false
	}
	got, err := parseCodexSemver(detectedVersion)
	if err != nil {
		return false
	}
	return !got.lessThan(fixed)
}

// codexUpgradeHint returns a short, actionable hint for users running a Codex
// version that suffers from the macOS network_access bug.
func codexUpgradeHint() string {
	return "upgrade Codex CLI (e.g. `brew upgrade codex` or `npm i -g @openai/codex`) once a release including openai/codex#10390 is available to restore workspace-write + network_access"
}

// multicaManagedBeginMarker / multicaManagedEndMarker delimit the block the
// daemon writes into the per-task config.toml. Everything between the markers
// is owned by the daemon and will be rewritten idempotently; anything outside
// the markers is preserved as-is.
const (
	multicaManagedBeginMarker = "# BEGIN multica-managed (do not edit; regenerated by daemon)"
	multicaManagedEndMarker   = "# END multica-managed"
)

// renderMulticaManagedBlock produces the managed block for the given policy.
//
// The block contains only top-level key=value assignments — no `[table]`
// headers — and uses TOML dotted-key syntax for nested values. This is
// important because the block is inserted into a user-owned config.toml:
//
//   - If the block opened a `[sandbox_workspace_write]` header, any user
//     content that happened to sit below it would be silently reparented into
//     that table.
//   - If the block were appended after a file that already ends inside some
//     other table (e.g. `[permissions.multica]`), a bare `sandbox_mode = ...`
//     key would be parsed as a child of that preceding table.
//
// Keeping the block as pure top-level dotted-key assignments, and placing it
// at the top of the file (see upsertMulticaManagedBlock), avoids both traps.
func renderMulticaManagedBlock(policy codexSandboxPolicy) string {
	var b strings.Builder
	b.WriteString(multicaManagedBeginMarker)
	b.WriteString("\n")
	b.WriteString(fmt.Sprintf("sandbox_mode = %q\n", policy.Mode))
	if policy.Mode == "workspace-write" {
		b.WriteString(fmt.Sprintf("sandbox_workspace_write.network_access = %t\n", policy.NetworkAccess))
		if len(policy.WritableRoots) > 0 {
			b.WriteString("sandbox_workspace_write.writable_roots = ")
			b.WriteString(renderTomlStringArray(policy.WritableRoots))
			b.WriteString("\n")
		}
	}
	b.WriteString(multicaManagedEndMarker)
	b.WriteString("\n")
	return b.String()
}

// renderTomlStringArray renders a TOML inline array of basic strings, e.g.
// ["/a/b", "/c d"]. Each element is quoted with Go's %q, whose escaping (\\,
// \", \n, …) is a subset of TOML basic-string escaping, so ordinary
// filesystem paths — including ones with spaces — round-trip safely.
func renderTomlStringArray(vals []string) string {
	parts := make([]string, len(vals))
	for i, v := range vals {
		parts[i] = fmt.Sprintf("%q", v)
	}
	return "[" + strings.Join(parts, ", ") + "]"
}

// managedBlockRe captures the daemon-owned block (including the surrounding
// markers and any trailing blank lines) so it can be replaced idempotently.
// `\n*` rather than `\n?` so reruns don't accumulate blank lines when the
// block coexists with another managed block (e.g. multi-agent) in the file.
var managedBlockRe = regexp.MustCompile(
	`(?ms)^` + regexp.QuoteMeta(multicaManagedBeginMarker) +
		`.*?^` + regexp.QuoteMeta(multicaManagedEndMarker) + `\n*`)

// upsertMulticaManagedBlock returns the config content with the multica-managed
// block placed at the very top of the file. Any previously written managed
// block is removed in place; user content outside the markers is preserved.
//
// The block is always hoisted to the top (rather than replaced in place or
// appended to EOF) so that its top-level keys are parsed at the TOML root,
// regardless of whether the user's config ends inside a table like
// `[permissions.multica]` or `[profiles.foo]`. Combined with the dotted-key
// form used by renderMulticaManagedBlock, this means the managed block neither
// leaks into nor inherits from any surrounding table scope.
func upsertMulticaManagedBlock(content string, policy codexSandboxPolicy) string {
	// Drop any previously written managed block (wherever it sits).
	content = managedBlockRe.ReplaceAllString(content, "")
	block := renderMulticaManagedBlock(policy)
	// Trim leading blank lines left behind by the removal so we don't grow
	// the file on every idempotent rewrite.
	content = strings.TrimLeft(content, "\n")
	if content == "" {
		return block
	}
	return block + "\n" + content
}

// stripLegacySandboxDirectives removes top-level `sandbox_mode = ...` lines
// and any `[sandbox_workspace_write]` section that would otherwise conflict
// with the managed block. This lets the daemon migrate tasks whose config.toml
// was produced by an older daemon that wrote those values inline.
//
// Only top-level entries are stripped; anything under an unrelated section
// header (like `[permissions.foo]`) is preserved untouched.
func stripLegacySandboxDirectives(content string) string {
	lines := strings.Split(content, "\n")
	out := make([]string, 0, len(lines))
	inLegacyWorkspaceWrite := false
	for _, line := range lines {
		trimmed := strings.TrimSpace(line)
		if strings.HasPrefix(trimmed, "[") {
			// Entering a new section. Exit legacy-tracking if we were in one.
			inLegacyWorkspaceWrite = trimmed == "[sandbox_workspace_write]"
			if inLegacyWorkspaceWrite {
				continue
			}
			out = append(out, line)
			continue
		}
		if inLegacyWorkspaceWrite {
			// Drop the legacy section body until the next section.
			continue
		}
		if strings.HasPrefix(trimmed, "sandbox_mode") {
			// Drop legacy top-level sandbox_mode declarations.
			continue
		}
		out = append(out, line)
	}
	return strings.Join(out, "\n")
}

// ensureCodexSandboxConfig writes the multica-managed sandbox block into the
// given config.toml according to the policy. It is idempotent: running it
// twice produces the same file contents. The file is created if it doesn't
// exist.
//
// The function logs (at warn level) when it falls back to danger-full-access
// on macOS so the incident is visible in daemon logs.
func ensureCodexSandboxConfig(configPath string, policy codexSandboxPolicy, detectedVersion string, logger *slog.Logger) error {
	data, err := os.ReadFile(configPath)
	if err != nil && !os.IsNotExist(err) {
		return fmt.Errorf("read config.toml: %w", err)
	}
	existing := string(data)

	// Drop inline sandbox_mode / [sandbox_workspace_write] from older daemon
	// versions so they don't collide with the managed block.
	if existing != "" && !managedBlockRe.MatchString(existing) {
		existing = stripLegacySandboxDirectives(existing)
	}

	updated := upsertMulticaManagedBlock(existing, policy)
	if updated == string(data) {
		return nil
	}

	if policy.Mode == "danger-full-access" && logger != nil {
		version := detectedVersion
		if version == "" {
			version = "unknown"
		}
		attrs := []any{
			"reason", policy.Reason,
			"codex_version", version,
			"config_path", configPath,
		}
		if policy.Hint != "" {
			attrs = append(attrs, "hint", policy.Hint)
		}
		logger.Warn("codex sandbox: running unsandboxed with danger-full-access", attrs...)
	}

	if err := os.WriteFile(configPath, []byte(updated), 0o644); err != nil {
		return fmt.Errorf("write config.toml: %w", err)
	}
	return nil
}

// --- small semver helper, scoped to this package to avoid an import cycle
// with server/pkg/agent. The agent package already has a similar parser; we
// duplicate the minimal bits here because execenv cannot depend on agent.

type codexSemver struct {
	Major, Minor, Patch int
}

var codexSemverRe = regexp.MustCompile(`v?(\d+)\.(\d+)\.(\d+)`)

func parseCodexSemver(raw string) (codexSemver, error) {
	m := codexSemverRe.FindStringSubmatch(raw)
	if m == nil {
		return codexSemver{}, fmt.Errorf("cannot parse version %q", raw)
	}
	maj, _ := strconv.Atoi(m[1])
	min, _ := strconv.Atoi(m[2])
	pat, _ := strconv.Atoi(m[3])
	return codexSemver{Major: maj, Minor: min, Patch: pat}, nil
}

func (v codexSemver) lessThan(o codexSemver) bool {
	if v.Major != o.Major {
		return v.Major < o.Major
	}
	if v.Minor != o.Minor {
		return v.Minor < o.Minor
	}
	return v.Patch < o.Patch
}