import { type Abi, type AbiFunction, type AbiStateMutability, type Address, type ContractFunctionArgs, type ContractFunctionName, encodeAbiParameters, getAddress, toFunctionSelector, toHex } from "viem";

import { ConstraintCondition, type Limit, LimitType, LimitUnlimited, LimitZero, type SessionConfig } from "../../utils/session.js";
import type { ContractWriteMutability, IndexedValues } from "./type-utils.js";
import { encodedInputToAbiChunks, getParameterChunkIndex, isDynamicInputType, isFollowedByDynamicInputType, msStringToSeconds } from "./utils.js";

export type PartialLimit = bigint | {
  limit: bigint;
  period?: string | bigint;
} | {
  limitType: "lifetime" | LimitType.Lifetime;
  limit: bigint;
} | {
  limitType: "unlimited" | LimitType.Unlimited;
} | {
  limitType: "allowance" | LimitType.Allowance;
  limit: bigint;
  period: string | bigint;
};

export type PartialCallPolicy = {
  address: Address;
  abi: Abi;
  functionName: string;
  maxValuePerUse?: bigint;
  valueLimit?: PartialLimit;
  constraints?: {
    index: number;
    value?: unknown;
    condition?: keyof typeof ConstraintCondition;
    limit?: PartialLimit;
  }[];
};

export interface TypesafePartialCallPolicy<
  abi extends Abi,
  functionName extends ContractFunctionName<abi, ContractWriteMutability>,
> extends PartialCallPolicy {
  abi: abi;
  functionName: functionName;
  // eslint-disable-next-line @typescript-eslint/ban-ts-comment
  // @ts-ignore
  constraints?: (IndexedValues<ContractFunctionArgs<abi, ContractWriteMutability, functionName>>[number] & {
    condition?: keyof typeof ConstraintCondition;
    limit?: PartialLimit;
  })[];
};

// Typesafety helper function
export const callPolicy = <
  abi extends Abi,
  functionName extends ContractFunctionName<abi, ContractWriteMutability>,
>(
  policy: TypesafePartialCallPolicy<abi, functionName>,
): PartialCallPolicy => policy as PartialCallPolicy;

export type PartialTransferPolicy = {
  to: Address;
  maxValuePerUse?: bigint;
  valueLimit?: PartialLimit;
};

export interface SessionPreferences {
  expiry?: string | bigint | Date;
  feeLimit?: PartialLimit;
  contractCalls?: PartialCallPolicy[];
  transfers?: PartialTransferPolicy[];
};

export const formatLimitPreferences = (limit: PartialLimit): Limit => {
  /* Just bigint was passed */
  if (typeof limit === "bigint") {
    return {
      limitType: LimitType.Lifetime,
      limit,
      period: 0n,
    };
  }

  /* LimitType was specified */
  if ("limitType" in limit) {
    if (limit.limitType === "lifetime" || limit.limitType === LimitType.Lifetime) {
      return {
        limitType: LimitType.Lifetime,
        limit: limit.limit,
        period: 0n,
      };
    } else if (limit.limitType === "unlimited" || limit.limitType === LimitType.Unlimited) {
      return {
        limitType: LimitType.Unlimited,
        limit: 0n,
        period: 0n,
      };
    } else if (limit.limitType === "allowance" || limit.limitType === LimitType.Allowance) {
      return {
        limitType: LimitType.Allowance,
        limit: limit.limit,
        period: typeof limit.period === "string" ? msStringToSeconds(limit.period) : limit.period,
      };
    }
    // eslint-disable-next-line @typescript-eslint/no-explicit-any
    throw new Error(`Invalid limit type: ${(limit as any).limitType}`);
  }

  /* LimitType not selected */
  if (limit.period) {
    return {
      limitType: LimitType.Allowance,
      limit: limit.limit,
      period: typeof limit.period === "string" ? msStringToSeconds(limit.period) : limit.period,
    };
  }
  return {
    limitType: LimitType.Lifetime,
    limit: limit.limit,
    period: 0n,
  };
};

export const formatDatePreferences = (date: string | bigint | Date): bigint => {
  if (typeof date === "string") {
    const now = Math.floor(new Date().getTime() / 1000);
    const seconds = msStringToSeconds(date);
    return BigInt(now) + seconds;
  }
  if (date instanceof Date) {
    const seconds = Math.floor(date.getTime() / 1000);
    return BigInt(seconds);
  }
  return date;
};

export function formatSessionPreferences(
  preferences: SessionPreferences,
  defaults: {
    expiresAt: bigint;
    feeLimit: Limit;
  },
): Omit<SessionConfig, "signer"> {
  return {
    expiresAt: preferences.expiry ? formatDatePreferences(preferences.expiry) : defaults.expiresAt,
    feeLimit: preferences.feeLimit ? formatLimitPreferences(preferences.feeLimit) : defaults.feeLimit,
    callPolicies: preferences.contractCalls?.map((policy) => {
      const allowedStateMutability: ContractWriteMutability[] = ["nonpayable", "payable"];
      const abiFunction = (policy.abi as Abi).find((fn) => fn.type === "function" && fn.name === policy.functionName && (allowedStateMutability as AbiStateMutability[]).includes(fn.stateMutability)) as AbiFunction;
      if (!abiFunction) throw new Error(`Function not found in the provided ABI: ${policy.functionName}`);

      const selector = toFunctionSelector(abiFunction);
      const valueLimit = policy.valueLimit ? formatLimitPreferences(policy.valueLimit) : LimitZero;

      return {
        target: getAddress(policy.address.toLowerCase()),
        maxValuePerUse: policy.maxValuePerUse ?? valueLimit.limit,
        valueLimit,
        selector: selector,
        constraints: policy.constraints?.map((constraint) => {
          const limit = constraint.limit ? formatLimitPreferences(constraint.limit) : LimitUnlimited;
          let condition = ConstraintCondition.Unconstrained;
          if (constraint.condition) {
            condition = ConstraintCondition[constraint.condition];
          } else if (constraint.value !== undefined && constraint.value !== null) {
            condition = ConstraintCondition.Equal;
          }

          const input = abiFunction.inputs[constraint.index];
          if (!input) {
            throw new Error(`Target function parameter not found in the provided ABI function. Provided at function ${policy.functionName}, index ${constraint.index}`);
          }

          const isDynamicType = isDynamicInputType(input.type);
          if (isDynamicType) {
            throw new Error(`Function parameters with dynamic types are not supported for constraint validation. Provided at function ${policy.functionName}, index ${constraint.index}`);
          }

          const isFollowedByDynamicType = isFollowedByDynamicInputType(abiFunction, constraint.index);
          if (isFollowedByDynamicType) {
            throw new Error(`Target function parameter is followed by a dynamic type parameter. Provided at function ${policy.functionName}, index ${constraint.index}`);
          }

          const startingAbiChunkIndex = getParameterChunkIndex(abiFunction, constraint.index);
          if (constraint.value === undefined || constraint.value === null) {
            return {
              index: BigInt(startingAbiChunkIndex),
              condition: ConstraintCondition.Unconstrained,
              refValue: toHex("", { size: 32 }),
              limit,
            };
          }

          const encodedInput = encodeAbiParameters([input], [constraint.value]);
          const abiBytesChunks = encodedInputToAbiChunks(encodedInput);
          const ALLOWED_OVERFLOW_CONDITIONS: ConstraintCondition[] = [
            ConstraintCondition.Unconstrained,
            ConstraintCondition.Equal,
            ConstraintCondition.NotEqual,
          ];
          const ALLOWED_OVERFLOW_LIMIT_TYPES: LimitType[] = [
            LimitType.Unlimited,
          ];

          if (
            abiBytesChunks.length > 1
            && (
              !ALLOWED_OVERFLOW_CONDITIONS.includes(condition) // Can't validate condition (e.g. < >) if value is split across multiple chunks
              || !ALLOWED_OVERFLOW_LIMIT_TYPES.includes(limit.limitType) // Can't validate limit if value is split across multiple chunks
            )
          ) {
            throw new Error(`Encoded input size of parameter at index ${constraint.index} of ${policy.functionName} exceeds the maximum size of 32 bytes: ${abiBytesChunks.length * 32} bytes`);
          };

          return abiBytesChunks.map((abiChunk, index) => ({
            index: BigInt(startingAbiChunkIndex + index),
            condition,
            refValue: abiChunk,
            limit,
          }));
        }).flat() ?? [],
      };
    }) ?? [],
    transferPolicies: preferences.transfers?.map((policy) => {
      const valueLimit = policy.valueLimit ? formatLimitPreferences(policy.valueLimit) : LimitZero;
      return {
        target: getAddress(policy.to.toLowerCase()),
        maxValuePerUse: policy.maxValuePerUse ?? valueLimit.limit,
        valueLimit,
      };
    }) ?? [],
  };
}