/**
 * Transforms a raw XO invitation into a flattened, template-enriched structure
 * suitable for UI display without manually resolving template references.
 *
 * The original invitation format is unchanged in storage and transport; this
 * function produces a read model that merges commit data with template metadata
 * (names, descriptions, icons, roles, etc.).
 */

import { mergeInvitationCommits } from "@xo-cash/engine";
import { binToHex } from "@bitauth/libauth";
import type {
  XOInvitation,
  XOInvitationCommit,
  XOInvitationInput,
  XOInvitationOutput,
  XOInvitationVariable,
  XOInvitationVariableValue,
  XOTemplate,
  XOTemplateInput,
  XOTemplateOutput,
  XOTemplateVariable,
} from "@xo-cash/types";

/**
 * View metadata copied from a template definition onto a resolved invitation item.
 */
interface TemplateViewMetadata {
  name?: string;
  description?: string;
  icon?: string;
}

/**
 * Role-specific view metadata from a template output definition.
 */
export interface ResolvedInvitationOutputRoleMetadata {
  name?: string;
  description?: string;
  icon?: string;
}

/**
 * A variable from invitation commits enriched with its template definition.
 */
export interface ResolvedInvitationVariable {
  entityIdentifier: string;
  variableIdentifier: string;
  roleIdentifier?: string;
  value: XOInvitationVariableValue;
  name?: string;
  description?: string;
  type?: string;
  hint?: string;
}

/**
 * A transaction input from invitation commits enriched with its template definition.
 */
export type ResolvedInvitationInput = XOInvitationInput & {
  entityIdentifier: string;
  name?: string;
  description?: string;
  icon?: string;
  unlockingScript?: string;
  omitChangeAmounts?: XOTemplateInput["omitChangeAmounts"];
};

/**
 * A transaction output from invitation commits enriched with its template definition.
 */
export type ResolvedInvitationOutput = XOInvitationOutput & {
  entityIdentifier: string;
  name?: string;
  description?: string;
  icon?: string;
  roles?: Record<string, ResolvedInvitationOutputRoleMetadata>;
  lockingScript?: string;
};

/**
 * Flattened, template-enriched invitation data for UI consumption.
 */
export interface ResolvedInvitationData {
  invitationIdentifier: string;
  templateIdentifier: string;
  actionIdentifier: string;
  variables: ResolvedInvitationVariable[];
  inputs: ResolvedInvitationInput[];
  outputs: ResolvedInvitationOutput[];
}

/**
 * Picks human-readable view fields from a template definition.
 */
function pickTemplateViewMetadata(
  definition: TemplateViewMetadata | undefined,
): TemplateViewMetadata {
  if (!definition) return {};

  return {
    ...(definition.name !== undefined && { name: definition.name }),
    ...(definition.description !== undefined && {
      description: definition.description,
    }),
    ...(definition.icon !== undefined && { icon: definition.icon }),
  };
}

/**
 * Picks variable metadata from a template variable definition.
 */
function pickTemplateVariableMetadata(
  definition: XOTemplateVariable | undefined,
): Pick<ResolvedInvitationVariable, "name" | "description" | "type" | "hint"> {
  if (!definition) return {};

  return {
    ...pickTemplateViewMetadata(definition),
    ...(definition.type !== undefined && { type: definition.type }),
    ...(definition.hint !== undefined && { hint: definition.hint }),
  };
}

/**
 * Picks input metadata from a template input definition.
 */
function pickTemplateInputMetadata(
  definition: XOTemplateInput | undefined,
): Pick<
  ResolvedInvitationInput,
  "name" | "description" | "icon" | "unlockingScript" | "omitChangeAmounts"
> {
  if (!definition) return {};

  return {
    ...pickTemplateViewMetadata(definition),
    ...(definition.unlockingScript !== undefined && {
      unlockingScript: definition.unlockingScript,
    }),
    ...(definition.omitChangeAmounts !== undefined && {
      omitChangeAmounts: definition.omitChangeAmounts,
    }),
  };
}

/**
 * Template display metadata layered onto a committed output.
 */
interface TemplateOutputMetadata {
  name?: string;
  description?: string;
  icon?: string;
  roles?: Record<string, ResolvedInvitationOutputRoleMetadata>;
  lockingScript?: string;
  valueSatoshis?: bigint | string;
  token?: XOTemplateOutput["token"];
}

/**
 * Picks output metadata from a template output definition.
 *
 * Committed output values (e.g. lockingBytecode) take precedence over template
 * defaults; display-oriented fields like name, description, and template
 * valueSatoshis expressions are layered on for UI rendering.
 */
function pickTemplateOutputMetadata(
  definition: XOTemplateOutput | undefined,
): TemplateOutputMetadata {
  if (!definition) return {};

  const roles = definition.roles
    ? Object.fromEntries(
        Object.entries(definition.roles).map(([roleId, roleDefinition]) => [
          roleId,
          pickTemplateViewMetadata(roleDefinition),
        ]),
      )
    : undefined;

  return {
    ...pickTemplateViewMetadata(definition),
    ...(roles !== undefined && Object.keys(roles).length > 0 && { roles }),
    ...(definition.lockingScript !== undefined && {
      lockingScript: definition.lockingScript,
    }),
    ...(definition.valueSatoshis !== undefined && {
      valueSatoshis: definition.valueSatoshis,
    }),
    ...(definition.token !== undefined && { token: definition.token }),
  };
}

/**
 * Enriches a committed variable with its template definition.
 */
function resolveVariable(
  variable: XOInvitationVariable,
  entityIdentifier: string,
  template: XOTemplate,
): ResolvedInvitationVariable {
  const definition = template.variables?.[variable.variableIdentifier];

  return {
    entityIdentifier,
    variableIdentifier: variable.variableIdentifier,
    ...(variable.roleIdentifier !== undefined && {
      roleIdentifier: variable.roleIdentifier,
    }),
    value: variable.value,
    ...pickTemplateVariableMetadata(definition),
  };
}

/**
 * Enriches a committed input with its template definition when an identifier is present.
 */
function resolveInput(
  input: XOInvitationInput,
  entityIdentifier: string,
  template: XOTemplate,
): ResolvedInvitationInput {
  const definition = input.inputIdentifier
    ? template.inputs?.[input.inputIdentifier]
    : undefined;

  return {
    entityIdentifier,
    ...input,
    ...pickTemplateInputMetadata(definition),
  };
}

/**
 * Enriches a committed output with its template definition when an identifier is present.
 */
function resolveOutput(
  output: XOInvitationOutput,
  entityIdentifier: string,
  template: XOTemplate,
): ResolvedInvitationOutput {
  const definition = output.outputIdentifier
    ? template.outputs?.[output.outputIdentifier]
    : undefined;
  const templateMetadata = pickTemplateOutputMetadata(definition);

  return {
    entityIdentifier,
    ...output,
    ...templateMetadata,
  } as ResolvedInvitationOutput;
}

/**
 * Converts hex or binary invitation bytecode fields to hex strings for display.
 */
function hexOrBinToHex(
  value: string | Uint8Array | undefined,
): string | undefined {
  if (value === undefined) {
    return undefined;
  }

  return typeof value === "string" ? value : binToHex(value);
}

/**
 * Normalizes a merged input row for UI display (hex strings, no encoding placeholders).
 */
function normalizeMergedInputForDisplay(input: XOInvitationInput): XOInvitationInput {
  const normalized: XOInvitationInput = { ...input };

  if (input.outpointTransactionHash !== undefined) {
    normalized.outpointTransactionHash = hexOrBinToHex(
      input.outpointTransactionHash,
    ) as XOInvitationInput["outpointTransactionHash"];
  }

  if (input.unlockingBytecode !== undefined) {
    const isPlaceholder =
      input.unlockingBytecode instanceof Uint8Array &&
      input.unlockingBytecode.length === 0;

    if (isPlaceholder) {
      delete normalized.unlockingBytecode;
    } else {
      normalized.unlockingBytecode = hexOrBinToHex(
        input.unlockingBytecode,
      ) as XOInvitationInput["unlockingBytecode"];
    }
  }

  if (normalized.sequenceNumber === 0) {
    delete normalized.sequenceNumber;
  }

  return normalized;
}

/**
 * Normalizes a merged output row for UI display (hex strings).
 */
function normalizeMergedOutputForDisplay(
  output: XOInvitationOutput,
): XOInvitationOutput {
  const normalized: XOInvitationOutput = { ...output };

  if (output.lockingBytecode !== undefined) {
    normalized.lockingBytecode = hexOrBinToHex(
      output.lockingBytecode,
    ) as XOInvitationOutput["lockingBytecode"];
  }

  return normalized;
}

/**
 * Recovers `outputIdentifier` from the source commit because the merger strips it
 * after template resolution.
 */
function findOutputIdentifierForMergedOutput(
  commit: XOInvitationCommit | undefined,
  mergedOutput: XOInvitationOutput,
): string | undefined {
  const outputs = commit?.data?.outputs ?? [];
  const mergedBytecodeHex = hexOrBinToHex(mergedOutput.lockingBytecode);

  for (const commitOutput of outputs) {
    if (commitOutput.outputIdentifier === undefined) {
      continue;
    }

    const commitBytecodeHex = hexOrBinToHex(commitOutput.lockingBytecode);

    if (
      mergedBytecodeHex !== undefined &&
      commitBytecodeHex !== undefined &&
      mergedBytecodeHex === commitBytecodeHex
    ) {
      return commitOutput.outputIdentifier;
    }
  }

  const outputsWithIdentifier = outputs.filter(
    (commitOutput) => commitOutput.outputIdentifier !== undefined,
  );

  if (outputsWithIdentifier.length === 1) {
    const soleIdentifiedOutput = outputsWithIdentifier[0];
    return soleIdentifiedOutput?.outputIdentifier;
  }

  return undefined;
}

/**
 * Whether two invitation variable rows refer to the same template variable slot.
 */
function matchesInvitationVariable(
  left: XOInvitationVariable,
  right: XOInvitationVariable,
): boolean {
  return (
    left.variableIdentifier === right.variableIdentifier &&
    left.roleIdentifier === right.roleIdentifier
  );
}

/**
 * Finds the entity that authored a merged variable by scanning invitation commits.
 * Last matching commit in array order wins. Best-effort until the engine orders
 * commits internally or exposes source attribution on merged variables.
 */
function findVariableEntityIdentifier(
  variable: XOInvitationVariable,
  commits: XOInvitationCommit[],
): string {
  let entityIdentifier = "";

  for (const commit of commits) {
    for (const commitVariable of commit.data?.variables ?? []) {
      if (matchesInvitationVariable(commitVariable, variable)) {
        entityIdentifier = commit.entityIdentifier;
      }
    }
  }

  return entityIdentifier;
}

/**
 * Returns template-enriched invitation data for UI display.
 *
 * Uses {@link mergeInvitationCommits} for inputs and outputs so `mergesWith`
 * extensions and transaction indices are resolved. Variables come from the merged
 * result and are enriched with template metadata. Commit ordering is delegated to
 * the engine merger.
 *
 * @param invitation - The raw invitation in standard XO format.
 * @param template - The template referenced by the invitation.
 * @returns Resolved invitation data ready for display.
 */
export function resolveCommitReferences(
  invitation: XOInvitation,
  template: XOTemplate,
): ResolvedInvitationData {
  const commits = invitation.commits ?? [];
  const commitsMap = new Map(
    commits.map((commit) => [commit.commitIdentifier, commit]),
  );

  const merged = mergeInvitationCommits(
    invitation as Parameters<typeof mergeInvitationCommits>[0],
    template,
  );

  if (merged === null) {
    return {
      invitationIdentifier: invitation.invitationIdentifier,
      templateIdentifier: invitation.templateIdentifier,
      actionIdentifier: invitation.actionIdentifier,
      variables: [],
      inputs: [],
      outputs: [],
    };
  }

  const variables = merged.variables.map((variable) =>
    resolveVariable(
      variable,
      findVariableEntityIdentifier(variable, commits),
      template,
    ),
  );

  const inputs = merged.inputs.map((mergedInput) => {
    const commit = commitsMap.get(mergedInput.sourceCommitIdentifier);
    const entityIdentifier = commit?.entityIdentifier ?? "";
    const {
      sourceCommitIdentifier: _sourceCommitIdentifier,
      mergesWith: _mergesWith,
      ...input
    } = mergedInput;

    return resolveInput(
      normalizeMergedInputForDisplay(input),
      entityIdentifier,
      template,
    );
  });

  const outputs = merged.outputs.map((mergedOutput) => {
    const commit = commitsMap.get(mergedOutput.sourceCommitIdentifier);
    const entityIdentifier = commit?.entityIdentifier ?? "";
    const {
      sourceCommitIdentifier: _sourceCommitIdentifier,
      mergesWith: _mergesWith,
      ...output
    } = mergedOutput;
    const outputIdentifier = findOutputIdentifierForMergedOutput(commit, output);
    const outputForDisplay = normalizeMergedOutputForDisplay(
      outputIdentifier !== undefined ? { ...output, outputIdentifier } : output,
    );

    return resolveOutput(outputForDisplay, entityIdentifier, template);
  });

  return {
    invitationIdentifier: invitation.invitationIdentifier,
    templateIdentifier: invitation.templateIdentifier,
    actionIdentifier: invitation.actionIdentifier,
    variables,
    inputs,
    outputs,
  };
}