package promptkit

import (
	"context"

	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
	"gitea.maximumdirect.net/eric/promptkit/internal/usecase"
)

// RequirementInspectionRequest selects a prompt and supplies caller context
// for requirement discovery. It requires no artifact bindings or credentials.
type RequirementInspectionRequest struct {
	PromptID      string
	PromptVersion string
	ProfileID     string
	Vars          map[string]string
	SessionID     string
}

// RequirementKind describes how a selected prompt may depend on an input or
// caller variable for the supplied context.
type RequirementKind string

const (
	// RequirementRequired identifies a declaration or definite access.
	RequirementRequired RequirementKind = "required"
	// RequirementConditional identifies a dependency whose reachability is
	// unresolved for the supplied context.
	RequirementConditional RequirementKind = "conditional"
	// RequirementOptional identifies a dependency known not to be required,
	// including a reference used only on a known skipped path.
	RequirementOptional RequirementKind = "optional"
)

// InputRequirement describes a declared or template-referenced prompt input.
type InputRequirement struct {
	Name        string
	Kind        RequirementKind
	Declared    bool
	ContentType *string
	Description *string
	Explanation string
}

// VariableRequirement describes a caller-map key referenced by a prompt.
type VariableRequirement struct {
	Name        string
	Kind        RequirementKind
	Supplied    bool
	Explanation string
}

// RequirementIssueCode identifies a limitation that can affect discovery.
type RequirementIssueCode string

const (
	RequirementIssueMissingVariable      RequirementIssueCode = "missing_variable"
	RequirementIssueInputContent         RequirementIssueCode = "input_content"
	RequirementIssueDynamicInputName     RequirementIssueCode = "dynamic_input_name"
	RequirementIssueUnsupportedConstruct RequirementIssueCode = "unsupported_construct"
)

// RequirementIssue describes one discovery limitation using safe summary
// text. Descriptions are not intended as machine-readable details.
type RequirementIssue struct {
	Code         RequirementIssueCode
	InputName    string
	VariableName string
	Description  string
}

// RequirementInspection contains discovered dependencies for one selected
// prompt context. Complete describes discovery, not renderability or readiness.
type RequirementInspection struct {
	PromptID      string
	PromptVersion string
	ProfileID     string
	Inputs        []InputRequirement
	Variables     []VariableRequirement
	Complete      bool
	Issues        []RequirementIssue
}

// InspectRequirements discovers inputs and caller variables for one selected
// prompt before its input artifacts exist. It uses exact, case-sensitive
// prompt selection and requires a profile ID either in the request or the
// selected prompt's default. The selected profile establishes identity only;
// it need not be execution-ready. A normalized nonblank SessionID bypasses the
// captured session template. Vars are copied before analysis, and returned
// slices and metadata pointers belong to the caller.
//
// This method does not perform artifact, schema, credential, rendering,
// validation, capacity, observation, provider, or execution work. Complete
// describes dependency discovery, not whether every dependency is supplied or
// the prompt is ready to execute. Discovery limitations return a partial
// inspection and no error; selection and operational failures return no
// inspection. Blank prompt IDs, invalid session IDs, and absent profile
// selection match ErrInvalidRequest; an absent profile selection also matches
// ErrProfileRequired. Missing prompt/profile IDs match ErrPromptNotFound or
// ErrProfileNotFound. Other selection/snapshot failures match ErrPromptLoad or
// ErrProfileLoad. A nil Engine matches ErrInvalidConfig.
func (e *Engine) InspectRequirements(
	ctx context.Context,
	req RequirementInspectionRequest,
) (*RequirementInspection, error) {
	if e == nil || e.internal == nil {
		return nil, ErrInvalidConfig
	}
	inspection, err := e.internal.InspectRequirements(ctx, usecase.RequirementInspectionRequest{
		PromptID: req.PromptID, PromptVersion: req.PromptVersion, ProfileID: req.ProfileID,
		Vars: copyStringMap(req.Vars), SessionID: req.SessionID,
	})
	if err != nil {
		return nil, mapPublicError(err)
	}
	return fromDomainRequirementInspection(inspection), nil
}

func fromDomainRequirementInspection(inspection *domain.RequirementInspection) *RequirementInspection {
	if inspection == nil {
		return nil
	}
	result := &RequirementInspection{
		PromptID: inspection.PromptID, PromptVersion: inspection.PromptVersion,
		ProfileID: inspection.ProfileID, Complete: inspection.Complete,
		Inputs:    make([]InputRequirement, len(inspection.Inputs)),
		Variables: make([]VariableRequirement, len(inspection.Variables)),
		Issues:    make([]RequirementIssue, len(inspection.Issues)),
	}
	for index, input := range inspection.Inputs {
		result.Inputs[index] = InputRequirement{
			Name: input.Name, Kind: RequirementKind(input.Kind), Declared: input.Declared,
			ContentType: copyRequirementString(input.ContentType), Description: copyRequirementString(input.Description),
			Explanation: input.Explanation,
		}
	}
	for index, variable := range inspection.Variables {
		result.Variables[index] = VariableRequirement{
			Name: variable.Name, Kind: RequirementKind(variable.Kind), Supplied: variable.Supplied,
			Explanation: variable.Explanation,
		}
	}
	for index, issue := range inspection.Issues {
		result.Issues[index] = RequirementIssue{
			Code: RequirementIssueCode(issue.Code), InputName: issue.InputName,
			VariableName: issue.VariableName, Description: issue.Description,
		}
	}
	return result
}

func copyRequirementString(value *string) *string {
	if value == nil {
		return nil
	}
	copy := *value
	return &copy
}