package tool

import (
	"context"
	"encoding/json"
	"fmt"

	llm "gitea.stevedudenhoeffer.com/steve/majordomo/llm"
)

// gatedToolMarker is the unexported interface implemented by every Tool
// constructed via NewGatedTool. The IsGatedTool helper performs a type
// assertion against this marker so the meta-test in default_test.go
// (and the wizardtools meta-test) can enforce that every registered
// production tool uses the wrapper.
//
// Why an unexported method (vs a public marker): the goal is to make it
// IMPOSSIBLE for an external caller to lie about being gated. Only the
// implementation in this file can satisfy the interface, so the
// type-assertion in IsGatedTool is a real proof of provenance, not a
// pinky-swear from a struct that opts in.
type gatedToolMarker interface {
	isGatedTool()
}

// gatedTool is the concrete Tool returned by NewGatedTool. It carries
// the per-tool metadata (Name/Description/Permission) and the typed
// handler closure; BuildLLM wraps the handler with CheckGate +
// EmitAudit so tool authors literally cannot forget either call.
//
// Why generic on Args (vs accepting any-shaped JSON): each tool's
// handler is typed against its own param struct. defineTypedTool
// derives a JSON schema for the LLM from Args (llm.SchemaFor) and
// parses the args before invoking the handler. We re-marshal args to
// JSON once for the audit row so the captured shape matches exactly
// what the handler ran with (post-coercion).
type gatedTool[Args any] struct {
	name        string
	description string
	permission  Permission
	fn          func(ctx context.Context, inv Invocation, args Args) (string, error)
}

// isGatedTool implements gatedToolMarker for the meta-test.
func (g *gatedTool[Args]) isGatedTool() {}

// defineTypedTool builds the majordomo llm.Tool for a typed handler:
// schema derived from Args, arguments decoded leniently (string→number/
// boolean coercion preserved from the legacy gollm era — see argcoerce.go)
// before the handler runs. An unparseable arguments object returns the
// decode error WITHOUT running fn, framing arg-parse-error as a
// tool-call wiring failure rather than a tool-handler failure.
//
// Why not majordomo's llm.DefineTool: its decode is strict by design;
// mort's tool catalog keeps the lenient dialect for parity with years
// of model traffic that emits "3" where the schema says integer.
func defineTypedTool[Args any](name, description string, fn func(ctx context.Context, args Args) (string, error)) llm.Tool {
	schema, err := llm.SchemaFor[Args]()
	if err != nil {
		panic(fmt.Sprintf("skilltools: defineTypedTool(%q): %v", name, err))
	}
	return llm.Tool{
		Name:        name,
		Description: description,
		Parameters:  schema,
		Handler: func(ctx context.Context, raw json.RawMessage) (any, error) {
			var args Args
			if err := unmarshalArgsLenient(raw, &args); err != nil {
				return nil, fmt.Errorf("invalid arguments for %s: %w", name, err)
			}
			return fn(ctx, args)
		},
	}
}

// NewGatedTool wraps a typed handler so it automatically:
//  1. Calls CheckGate(inv) before the handler runs. On gate rejection
//     emits EmitAudit(inv, "{}", "", err) and returns the gate error.
//  2. Calls fn(ctx, inv, args) once gate passes.
//  3. Re-marshals args to JSON for the audit row (so the captured args
//     reflect any coercion performed during deserialisation), then
//     emits EmitAudit(inv, argsJSON, result, err) once the handler
//     returns.
//
// Production tools SHOULD use NewGatedTool unless they have a strong
// reason to handle gating manually. The wrapper exists because the
// previous per-tool pattern repeated four lines of boilerplate
// (CheckGate at the top, EmitAudit on every return path), and that
// boilerplate is easy to forget — wizard tools in v1 hotfix #4 had to
// be retrofitted because the author overlooked CheckGate. Centralising
// the calls makes them impossible to skip and the meta-test in
// tools/default_test.go enforces the discipline.
//
// The typed define layer handles JSON parsing and arg coercion before
// fn runs; if the args JSON is unparseable, the decode error is
// returned directly (the wrapper's audit emission does NOT fire on
// parse error — arg-parse-error is a tool-call wiring failure rather
// than a tool-handler failure).
//
// Test: pkg/skilltools/gated_tool_test.go covers gate rejection,
// happy path, fn-returned error, and the IsGatedTool assertion. The
// meta-test in pkg/skilltools/tools/default_test.go walks the registry
// and asserts every production tool implements gatedToolMarker.
func NewGatedTool[Args any](
	name, description string,
	permission Permission,
	fn func(ctx context.Context, inv Invocation, args Args) (string, error),
) Tool {
	return &gatedTool[Args]{
		name:        name,
		description: description,
		permission:  permission,
		fn:          fn,
	}
}

// Name returns the tool's registry key.
func (g *gatedTool[Args]) Name() string { return g.name }

// Description is shown to the LLM.
func (g *gatedTool[Args]) Description() string { return g.description }

// Permission classifies the tool for save-time / share-time gating.
func (g *gatedTool[Args]) Permission() Permission { return g.permission }

// BuildLLM produces the per-invocation llm.Tool. The returned tool's
// handler:
//   - Runs CheckGate(inv) FIRST (before any handler logic). On gate
//     rejection emits the audit row and returns the gate error.
//   - Calls the user-supplied fn with the typed args. fn never sees a
//     gate-rejected invocation.
//   - Re-marshals args to JSON and emits the audit row exactly once,
//     regardless of fn's return value (success or error).
//
// Why re-marshal vs using the raw LLM JSON: the lenient decode performs
// numeric/boolean coercion (e.g. "3" → 3) before invoking the handler;
// the audit row should reflect what fn actually received, not the
// pre-coercion text the LLM emitted.
func (g *gatedTool[Args]) BuildLLM(inv Invocation) llm.Tool {
	return defineTypedTool[Args](
		g.name,
		g.description,
		func(ctx context.Context, args Args) (string, error) {
			if err := CheckGate(inv); err != nil {
				EmitAudit(inv, "{}", "", err)
				return "", err
			}
			argsJSON, mErr := json.Marshal(args)
			if mErr != nil {
				// Vanishingly rare for the typed param structs in use;
				// fall back to "{}" so the audit row never carries a
				// half-formed args field.
				argsJSON = []byte("{}")
			}
			result, err := g.fn(ctx, inv, args)
			EmitAudit(inv, string(argsJSON), result, err)
			return result, err
		},
	)
}

// IsGatedTool reports whether t was constructed via NewGatedTool /
// NewGatedToolWithAudit. Used by the meta-test in
// tools/default_test.go to enforce that every registered production
// tool uses the wrapper. The check is a type assertion against the
// unexported gatedToolMarker interface, so only the gatedTool variants
// from this package can satisfy it — there is no way for an external
// Tool to pretend to be gated.
func IsGatedTool(t Tool) bool {
	_, ok := t.(gatedToolMarker)
	return ok
}

// AuditedResult is what a NewGatedToolWithAudit handler returns:
// LLMResult is the string surfaced to the LLM (the tool-call result
// the model sees in its conversation); AuditArgs and AuditResult are
// what the wrapper logs to the audit row INSTEAD of the auto-derived
// values.
//
// Why a separate variant: a small number of tools (paste_create being
// the canonical example) need to return a sensitive value to the LLM
// (a URL containing an encryption-key fragment) but MUST redact that
// value from the audit row, since the audit row is rendered to admins
// in the webui run-trace view. The default wrapper auto-logs args +
// result, which would leak the key. NewGatedToolWithAudit lets the
// handler explicitly separate the LLM-visible output from the
// audit-visible output, while still benefitting from auto-injected
// CheckGate.
type AuditedResult struct {
	// LLMResult is the string returned to the LLM as the tool result.
	LLMResult string
	// AuditArgs is the args string written to the audit row. If empty,
	// the wrapper falls back to the JSON-marshaled typed args (same
	// behaviour as NewGatedTool).
	AuditArgs string
	// AuditResult is the result string written to the audit row. May
	// be empty (logged as "") to suppress sensitive fragments.
	AuditResult string
}

// gatedToolWithAudit is the variant of gatedTool whose handler returns
// an AuditedResult so it can override what the audit row captures.
type gatedToolWithAudit[Args any] struct {
	name        string
	description string
	permission  Permission
	fn          func(ctx context.Context, inv Invocation, args Args) (AuditedResult, error)
}

// isGatedTool implements gatedToolMarker for the meta-test.
func (g *gatedToolWithAudit[Args]) isGatedTool() {}

func (g *gatedToolWithAudit[Args]) Name() string           { return g.name }
func (g *gatedToolWithAudit[Args]) Description() string    { return g.description }
func (g *gatedToolWithAudit[Args]) Permission() Permission { return g.permission }

// NewGatedToolWithAudit is the redaction-aware variant of NewGatedTool.
// Use it ONLY when the LLM-facing result must differ from the audit
// row (e.g. the result contains an encryption key that the audit must
// NOT capture). Most tools should use NewGatedTool.
//
// Behaviour matches NewGatedTool exactly except:
//   - The handler returns AuditedResult; the wrapper passes
//     AuditedResult.LLMResult to the LLM and writes
//     AuditedResult.AuditArgs / AuditedResult.AuditResult to the
//     audit row (falling back to the JSON-marshaled args if
//     AuditArgs is empty).
//   - Gate rejection still emits an audit row with empty Result and
//     args="{}" before returning the gate error.
//
// Test: covered alongside NewGatedTool in pkg/skilltools/
// gated_tool_test.go.
func NewGatedToolWithAudit[Args any](
	name, description string,
	permission Permission,
	fn func(ctx context.Context, inv Invocation, args Args) (AuditedResult, error),
) Tool {
	return &gatedToolWithAudit[Args]{
		name:        name,
		description: description,
		permission:  permission,
		fn:          fn,
	}
}

// BuildLLM produces the per-invocation llm.Tool. Same gate-injection
// semantics as gatedTool[Args].BuildLLM; the audit row uses the
// handler-supplied AuditArgs / AuditResult so a sensitive LLM-visible
// result string never leaks into the audit log.
func (g *gatedToolWithAudit[Args]) BuildLLM(inv Invocation) llm.Tool {
	return defineTypedTool[Args](
		g.name,
		g.description,
		func(ctx context.Context, args Args) (string, error) {
			if err := CheckGate(inv); err != nil {
				EmitAudit(inv, "{}", "", err)
				return "", err
			}
			res, err := g.fn(ctx, inv, args)
			auditArgs := res.AuditArgs
			if auditArgs == "" {
				if b, mErr := json.Marshal(args); mErr == nil {
					auditArgs = string(b)
				} else {
					auditArgs = "{}"
				}
			}
			EmitAudit(inv, auditArgs, res.AuditResult, err)
			return res.LLMResult, err
		},
	)
}