package builtin

import (
	"context"
	"fmt"
	"os"
	"path/filepath"
	"runtime"
	"strings"
	"time"

	"reasonix/internal/netclient"
	"reasonix/internal/sandbox"
	"reasonix/internal/secrets"
	"reasonix/internal/tool"
)

// ConfineBash returns the bash built-in bound to an OS-sandbox spec, overriding
// the unconfined instance registered at init. When the spec enforces, bash runs
// each command through the sandbox (see package sandbox). guard appends a
// warning to command output when the command references Reasonix's own session
// stores (see SessionDataGuard).
func ConfineBash(spec sandbox.Spec, guard SessionDataGuard, timeout ...time.Duration) tool.Tool {
	shell := spec.Shell
	if shell.Path == "" {
		shell = sandbox.ResolveShell("", "", nil)
	}
	b := bash{sb: spec, shell: shell, guard: guard}
	if len(timeout) > 0 {
		b.timeout = timeout[0]
	}
	return b
}

// ConfineWebFetch returns the web_fetch built-in bound to Reasonix proxy
// settings while preserving its SSRF-guarded dialer.
func ConfineWebFetch(proxySpec netclient.ProxySpec) tool.Tool {
	return webFetch{proxySpec: proxySpec}
}

// ConfineWriters returns the file-writing built-ins (write_file, edit_file,
// multi_edit, move_file, notebook_edit) bound to roots — the only directories they may
// modify. The composition root adds these to the per-run registry to override
// the unconfined instances registered at init time, so writes stay inside the
// workspace by default. roots may be relative; they are resolved to absolute,
// symlink-free paths once here. An empty roots slice yields unconfined writers.
// guard additionally rejects writes into Reasonix's own session stores even
// when the roots would allow them (see SessionDataGuard). managed names the
// Reasonix-owned config files writable outside the roots after a fresh human
// approval (see ManagedConfigPaths).
func ConfineWriters(roots []string, guard SessionDataGuard, managed ManagedConfigPaths) []tool.Tool {
	rs := realRoots(roots)
	return []tool.Tool{
		writeFile{roots: rs, guard: guard, managed: managed},
		editFile{roots: rs, guard: guard, managed: managed},
		multiEdit{roots: rs, guard: guard, managed: managed},
		moveFile{roots: rs, guard: guard, managed: managed},
		notebookEdit{roots: rs, guard: guard, managed: managed},
		deleteRange{roots: rs, guard: guard, managed: managed},
		deleteSymbol{roots: rs, guard: guard, managed: managed},
	}
}

// ConfineReaders returns the read/list/search built-ins (read_file, glob,
// ls, code_index) bound to forbidRoots — directories the agent may not read or list.
// grep is handled separately by ConfineSearch so it can carry the
// sandbox spec for its ripgrep subprocess.
// An empty forbidRoots slice yields unconfined readers.
func ConfineReaders(forbidRoots []string) []tool.Tool {
	rs := realRoots(forbidRoots)
	return []tool.Tool{
		readFile{forbidRoots: rs},
		listDir{forbidRoots: rs},
		globTool{forbidRoots: rs},
		codeIndex{forbidRoots: rs},
	}
}

// confineRead reports whether target is inside any forbidRoot or, when the
// user enabled [secrets] protect_sensitive_files, matches Reasonix's built-in
// sensitive credential path denylist. An empty forbidRoots slice with the
// denylist off is unconfined (returns false). Callers should return a result
// that mimics the directory appearing empty, matching the tmpfs semantics the
// bubblewrap sandbox provides. Deny-side, so the check folds case on
// case-insensitive platforms (see withinFold): a case-variant of a forbidden
// path reaches the same bytes there.
func confineRead(forbidRoots []string, target string) bool {
	protect := secrets.ProtectSensitiveFiles()
	if len(forbidRoots) == 0 && !protect {
		return false
	}
	abs, err := realPath(target)
	if err != nil {
		return false // can't resolve -> let the caller's normal error path handle it
	}
	if protect && sensitiveReadPath(abs) {
		return true
	}
	for _, r := range forbidRoots {
		if withinFold(r, abs) {
			return true
		}
	}
	return false
}

func sensitiveReadPath(abs string) bool {
	clean := filepath.Clean(abs)
	name := strings.ToLower(filepath.Base(clean))
	switch name {
	case ".env", ".git-credentials", ".netrc":
		return true
	}
	for _, ext := range []string{".pem", ".key", ".p12", ".pfx"} {
		if strings.HasSuffix(name, ext) {
			return true
		}
	}
	home, err := os.UserHomeDir()
	if err == nil && home != "" {
		if withinFold(filepath.Join(home, ".ssh"), clean) {
			return true
		}
	}
	return false
}

// realRoots resolves each root to an absolute, symlink-free path, dropping any
// that cannot be made absolute. Resolving here (once) means the per-call check
// only has to resolve the target.
func realRoots(roots []string) []string {
	out := make([]string, 0, len(roots))
	for _, r := range roots {
		if real, err := realPath(r); err == nil {
			out = append(out, real)
		}
	}
	return out
}

// confine reports an error when target resolves outside every root. An empty
// roots slice is unconfined (returns nil) — the safe default for the built-in
// templates before a run configures the workspace. The error text is written
// for the model: it names the boundary and how the user can widen it.
func confine(roots []string, target string) error {
	if len(roots) == 0 {
		return nil
	}
	abs, err := realPath(target)
	if err != nil {
		return fmt.Errorf("resolve %s: %w", target, err)
	}
	for _, r := range roots {
		if within(r, abs) {
			return nil
		}
	}
	return fmt.Errorf("path %q is outside the writable roots (writes are confined to %s); "+
		"write inside the workspace or a configured allow_write root, or widen [sandbox] workspace_root / allow_write in reasonix.toml",
		target, strings.Join(roots, ", "))
}

// confineWrite is the write-tool boundary check: workspace confinement first,
// then the session-data guard, so a write can be inside the roots (e.g. a
// home-directory workspace covering the state root) and still be refused when
// it targets Reasonix's own session stores. A target outside every root that
// matches a Reasonix-managed config file (see ManagedConfigPaths) may proceed
// after a fresh per-write human approval carried on ctx; without an approver it
// fails closed with the original confinement error semantics.
func confineWrite(ctx context.Context, roots []string, guard SessionDataGuard, managed ManagedConfigPaths, target string) error {
	confineErr := confine(roots, target)
	if confineErr == nil {
		return guard.Check(target)
	}
	if !managed.Match(target) {
		return confineErr
	}
	if err := guard.Check(target); err != nil {
		return err
	}
	return managed.approve(ctx, target)
}

// confinePreview mirrors confineWrite for ctx-less diff previews: they read the
// target to render a diff but never write, so a managed config file passes
// without the per-write approval — Execute still gates the actual write.
func confinePreview(roots []string, guard SessionDataGuard, managed ManagedConfigPaths, target string) error {
	confineErr := confine(roots, target)
	if confineErr == nil {
		return guard.Check(target)
	}
	if !managed.Match(target) {
		return confineErr
	}
	return guard.Check(target)
}

// realPath resolves path to an absolute, symlink-free form. Because a write
// target need not exist yet (write_file creates it), it resolves the deepest
// existing ancestor with EvalSymlinks and re-appends the not-yet-existing tail.
// This stops a symlinked directory from smuggling a write outside a root.
func realPath(path string) (string, error) {
	abs, err := filepath.Abs(path)
	if err != nil {
		return "", err
	}
	abs = filepath.Clean(abs)
	tail := ""
	cur := abs
	for {
		if real, err := filepath.EvalSymlinks(cur); err == nil {
			return filepath.Join(real, tail), nil
		}
		parent := filepath.Dir(cur)
		if parent == cur {
			return abs, nil // nothing along the path exists; use the cleaned abs
		}
		tail = filepath.Join(filepath.Base(cur), tail)
		cur = parent
	}
}

// within reports whether path is at or below root. Both must be absolute,
// cleaned, symlink-free. It uses filepath.Rel so it is correct across volumes
// and is not fooled by a prefix that only matches a partial path component
// (e.g. /work-other is not within /work).
func within(root, path string) bool {
	rel, err := filepath.Rel(root, path)
	if err != nil {
		return false
	}
	return rel == "." || (rel != ".." && !strings.HasPrefix(rel, ".."+string(filepath.Separator)))
}

// foldPaths reports whether deny-side path checks on this platform must ignore
// case: the default filesystems on Windows (NTFS) and macOS (APFS/HFS+) are
// case-insensitive, so /X/SESSIONS and /x/sessions reach the same bytes and a
// case-variant must not slip past a deny rule. EvalSymlinks does NOT normalize
// case, so realPath alone cannot be relied on for this.
var foldPaths = runtime.GOOS == "windows" || runtime.GOOS == "darwin"

// withinFold is within with platform case folding, for DENY-side checks only
// (forbid-read roots, the session-data guard). Allow-side checks (confine)
// keep the exact within: folding an allow rule on a case-sensitive filesystem
// would wave a genuinely different directory through, whereas folding a deny
// rule only ever refuses more. On a case-sensitive macOS volume this can
// refuse a legitimate same-letters-different-case path; the error text points
// at allow_write / forbid_read config as the way out.
func withinFold(root, path string) bool {
	if foldPaths {
		return within(strings.ToLower(root), strings.ToLower(path))
	}
	return within(root, path)
}